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PubMed2004

Nitrogen nutrition and isotopic discrimination in tropical ectomycorrhizal fungi.

It is known that many ectomycorrhizal (EcM) fungi are able to utilise complex organic sources of nitrogen. Two hypotheses were tested using isolates of tropical EcM fungi grown in vitro: (i) EcM fungi isolated from mineral soils of tropical rain forests are less able to utilise organic sources of nitrogen than mineral sources; and (ii) nitrogen isotope discrimination patterns follow those of the nitrogen source utilised. Pisolithus albus and Tomentella sp. represented tropical EcM fungi and they were grown along with Thelephora terrestris. All three species were able to utilise bovine serum albumen as a nitrogen source and P. albus produced the greatest biomass on this source of nitrogen. Nitrate was generally less well utilised than ammonium although all three species were able to grow on this nitrogen source. The nitrogen source which led to the greatest biomass also led to the highest fungal nitrogen concentration in P. albus and Tomentella sp., but not T. terrestris. All three species discriminated against (15)N when grown on BSA and NO(3) but there were interspecific differences in isotope discrimination when grown on NH(4). From a limited number of isolates, it was found that EcM fungi from tropical soils utilise protein nitrogen as well as mineral nitrogen and there can be considerable nitrogen isotope discrimination during the utilisation of all these nitrogen sources.

Acacia↗
PubMed2003

Nitrogen metabolism and virulence of Candida albicans require the GATA-type transcriptional activator encoded by GAT1.

Nitrogen acquisition and metabolism is central to microbial growth. A conserved family of zinc-finger containing transcriptional regulators known as GATA-factors ensures efficient utilization of available nitrogen sources by fungi. GATA factors activate expression of nitrogen catabolic pathways when preferred nitrogen sources are absent or limiting, a phenomenon known as nitrogen catabolite repression. GAT1 of Candida albicans encodes a GATA-factor homologous to the AREA protein of Aspergillus nidulans and related transcription factors involved in nitrogen regulation. Two observations implicated GAT1 in nitrogen regulation. The growth of mutants lacking GAT1 was reduced when isoleucine, tyrosine or tryptophan were the sole source of nitrogen. Secondly, when cultured on a secondary nitrogen source, gat1Delta mutants were unable to activate expression of GAP1, UGA4 or DAL5, which were shown to be nitrogen regulated in C. albicans. This regulatory defect did not prevent filamentation of gat1Delta mutants in nitrogen repressing or non-repressing conditions, demonstrating that nitrogen catabolite repression does not influence dimorphism. The mutants were, however, highly attenuated in a murine model of disseminated candidiasis. Attenuation was not associated with any diminution of growth in serum or ability to utilize serum amino acids. The results indicate an important role for nitrogen regulation in the virulence of C. albicans.

Amino Acid Sequence↗
PubMed2006

Ammonia excretion increased and urea excretion decreased in urine of a new world nectarivorous bat with decreased nitrogen intake.

We determined the effect of water and nitrogen intake on nitrogenous waste composition in the nectarivorous Pallas's long-tongued bat Glossophaga soricina (Phyllostomidae) to test the hypothesis that bats reduce excretion of urea nitrogen and increase the excretion of ammonia nitrogen as nitrogen intake decreases and water intake decreases. Because changes in urine nitrogen composition are expected only in animals whose natural diets are low in nitrogen and high in water content, we also measured maintenance nitrogen requirements (MNR). We hypothesized that, similar to other plant-eating vertebrates, nectarivorous bats have low MNR. Our nitrogen excretion hypothesis was partly proved correct. There was an increase in the proportion of N excreted as ammonia and a decrease in the proportion excreted as urea in low-nitrogen diets. The proportion of N excreted as ammonia and urea was independent of water intake. Most individuals were ureotelic (n = 28), and only a few were ureo-ammonotelic (n = 3) or ammonotelic (n = 2). According to our nitrogen requirement hypothesis, apparent MNR (60 mg kg(-0.75) d(-1)) and truly digestible MNR (54 mg N kg(-0.75) d(-1)) were low. A decrease in urea excretion in low-nitrogen diets may result from urea recycling from liver to the gut functioning as a nitrogen salvage system in nectarivorous bats. This mechanism probably contributes to the low MNR found in Pallas's long-tongued bats.

Ammonia↗
PubMed2007

Nitrogen balance, protein loss, and the open abdomen.

OBJECTIVE: Goal-directed nutritional support is essential to improving morbidity and mortality. Open abdominal decompression is similarly crucial to the successful treatment of intra-abdominal hypertension and abdominal compartment syndrome. The open abdomen, however, places the patient at risk for potentially significant fluid, electrolyte, and presumably protein losses from the exposed viscera. Although nutritional protein assessments are frequently utilized to measure urinary nitrogen, these calculations do not consider the loss of protein from the open abdomen. We hypothesize that accurate assessment of nitrogen balance in the patient requiring an open abdomen must include either a measurement or estimation of abdominal fluid nitrogen loss. DESIGN: Prospective, observational cohort study. SETTING: Adult surgical/trauma intensive care unit of a level I trauma center. PATIENTS: Surgical/trauma patients requiring laparotomy. INTERVENTIONS: Serial 24-hr collections of urine and abdominal fluid protein were performed to characterize abdominal fluid protein loss and evaluate the clinical effect of accounting for abdominal fluid nitrogen as part of nitrogen balance calculations. MEASUREMENTS AND MAIN RESULTS: Nitrogen intake correlates with urinary nitrogen loss but not with abdominal fluid nitrogen loss. Abdominal fluid nitrogen loss is significant and remains relatively stable in the early postoperative period. Nutritional calculations that fail to account for abdominal fluid nitrogen loss significantly overestimate actual nitrogen balance by an average of 3.5 g/24 hrs. CONCLUSIONS: The open abdomen represents a significant source of protein/nitrogen loss in the critically ill. Failure to account for this loss in nutritional calculations may lead to underfeeding and inadequate nutritional support with a direct effect on patient outcome. Although direct measurement of abdominal fluid protein loss may be optimal, an estimate of 2 g of nitrogen per liter of abdominal fluid output should be included in the nitrogen balance calculations of any patient with an open abdomen.

Abdominal Cavity↗
PubMed2003

Nitrogen fixation in the activated sludge treatment of thermomechanical pulping wastewater: effect of dissolved oxygen.

N-ViroTech, a novel technology which selects for nitrogen-fixing bacteria as the bacteria primarily responsible for carbon removal, has been developed to treat nutrient limited wastewaters to a high quality without the addition of nitrogen, and only minimal addition of phosphorus. Selection of the operating dissolved oxygen level to maximise nitrogen fixation forms a key component of the technology. Pilot scale activated sludge treatment of a thermomechanical pulping wastewater was carried out in nitrogen-fixing mode over a 15 month period. The effect of dissolved oxygen was studied at three levels: 14% (Phase 1), 5% (Phase 2) and 30% (Phase 3). The plant was operated at an organic loading of 0.7-1.1 kg BOD5/m3/d, a solids retention time of approximately 10 d, a hydraulic retention time of 1.4 d and a F:M ratio of 0.17-0.23 mg BOD5/mg VSS/d. Treatment performance was very stable over the three dissolved oxygen operating levels. The plant achieved 94-96% BOD removal, 82-87% total COD removal, 79-87% soluble COD removal, and >99% total extractives removal. The lowest organic carbon removals were observed during operation at 30% DO but were more likely to be due to phosphorus limitation than operation at high dissolved oxygen, as there was a significant decrease in phosphorus entering the plant during Phase 3. Discharge of dissolved nitrogen, ammonium and oxidised nitrogen were consistently low (1.1-1.6 mg/L DKN, 0.1-0.2 mg/L NH4+-N and 0.0 mg/L oxidised nitrogen). Discharge of dissolved phosphorus was 2.8 mg/L, 0.1 mg/L and 0.6 mg/L DRP in Phases 1, 2 and 3 respectively. It was postulated that a population of polyphosphate accumulating bacteria developed during Phase 1. Operation at low dissolved oxygen during Phase 2 appeared to promote biological phosphorus uptake which may have been affected by raising the dissolved oxygen to 30% in Phase 3. Total nitrogen and phosphorus discharge was dependent on efficient secondary clarification, and improved over the course of the study as suspended solids discharge improved. Nitrogen fixation was demonstrated throughout the study using an acetylene reduction assay. Based on nitrogen balances around the plant, there was a 55, 354 and 98% increase in nitrogen during Phases 1, 2 and 3 respectively. There was a significant decrease in phosphorus between Phases 1 and 2, and Phase 3 of the study, as well as a significant increase in nitrogen between Phases 2 and 3 which masked the effect of changing the dissolved oxygen. Operation at low dissolved oxygen appeared to confer a competitive advantage to the nitrogen-fixing bacteria.

Bioreactors↗
PubMed2003

[Dynamic simulation of nitrogen application level effects on rice yield and optimization analysis of fertilizer supply in paddy field].

Field and water tank plot experiments were conducted in Zhejiang Province in 1999 to determine the effects of nitrogen application amount and times on rice growth and yield, and rice growth simulation model ORYZA-0 and nitrogen management module were used to establish a modified nitrogen effect-rice growth model. The simulated results presented a higher positive relationship with the measured results. According to the simulated and measured results, 160 kg.hm-2 was the economic nitrogen application amount for two rice varieties production, and the nitrogen application strategies were: 1) < 100 kg.hm-2 nitrogen fertilizer should be applied within 35 days after transplanting; 2) when the nitrogen application level was between 100-200 kg.hm-2, it should be applied within 45 days after transplanting; 3) if the nitrogen application amount exceeded 200 kg.hm-2, it should be put into paddy field within 60 days after transplanting; 4) as the nitrogen application amount increased, the nitrogen supply at the later rice growth stage should be increased. As for the second cropping rice, the more times the nitrogen applied in the field, the more closeness the rice yield reached the APCUM curve(optimized nitrogen curve) suggested. But in real rice production, it is impossible for farmers to adopt more times of N applying, since labor and cost will increase. Based on the experimental parameters and real rice production situation, the reasonable nitrogen application under 160 kg.hm-2 levels for high yielding second cropping rice was split into 4 times with fraction 0.2:0.3:0.3:0.2 at 5, 20, 30, 40 days after transplanting. The rice yield could reach 5,916 kg.hm-2, resulted in a 3.12% increase as compared with the yield under actual fertilizer application amount and timing.

Crops, Agricultural↗
PubMedDate not supplied

[Synthesis of the nitrogen-fixing enzyme system in oligonitrophilic bacteria].

Oligonitrophilic bacteria were cultivated on a medium containing only 2.5--10.0 mg/litre of nitrogen compounds. They assimilated elementary nitrogen only after utilization of these nitrogen compounds during growth and formation of nitrogen-fixing enzyme system. Their cells grown on a medium containing high concentrations of bound nitrogen did not fix nitrogen during further incubation in the atmosphere of 15N; therefore, the enzymes involved in nitrogen fixation were induced. These organisms are characterized by diauxia during their growth on media containing "start" doses of nitrogen. Enzymes catalysing nitrogen fixation in azotobacter are also induced. But, contrary to oligonitrophilic bacteria, the azotobacter does not require nitrogen compounds in the medium in order to adapt to molecular nitrogen, and its growth curve is not of a biphasal character. These data and the evidence of other authors suggest that all nitrogen-fixing microorganisms are characterized by the induced, not constitutive, enzymes involved in reduction of molecular nitrogen.

Bacillus↗
PubMedDate not supplied

Root adaptation and nitrogen source acquisition in natural ecosystems.

The capacity for nitrate reduction, as measured by nitrate reductase activity (NRA), was generally low for a range of plant communities in Australia (coastal heathland, rainforest, savanna woodland, monsoon forest, mangrove, open Eucalyptus forest, coral cay open forest) and only a loose relationship existed between NRA and leaf nitrogen concentration. This suggests that nitrate ions are not the sole nitrogen source in these communities. Based on (15)N labeling experiments, we found a range of tree species exhibiting a pronounced preference for uptake of ammonium over nitrate. Analysis of soil solutions from several forest and heathland communities indicated that ammonium ions were more prevalent than nitrate ions and that soluble forms of organic nitrogen (amino acids and protein) were present in concentrations similar to those of mineral nitrogen. To determine the extent to which root adaptations and associations might broaden nitrogen source utilization to include organic nitrogen, we assessed the effects of various nitrogen sources on seedling growth in sterile culture. Non-mycorrhizal seedlings of Eucalyptus grandis W. Hill ex Maiden and Eucalyptus maculata Hook. grew well on mineral sources of nitrogen, but did not grow on organic sources of nitrogen other than glutamine. Mycorrhizal seedlings grew well on a range of organic nitrogen sources. When offered a mixture of inorganic and organic nitrogen sources at low concentrations, mycorrhizal seedlings derived a significant proportion of their nitrogen budget from organic sources. We also demonstrated that a species of the obligately non-mycorrhizal genus Hakea, a heathland proteaceous shrub possessing cluster roots, had the ability to incorporate (15)N-labeled organic sources (e.g., glycine). We conclude that mycorrhizal associations and root adaptations confer the ability to substantially broaden the nitrogen source base on some plant species.

Journal Article↗
PubMed1982

[N]NMR determination of asparagine and glutamine nitrogen utilization for synthesis of storage protein in developing cotyledons of soybean in culture.

Solid-state [(15)N]NMR was used to measure the use of the amide and amino nitrogens of glutamine and asparagine for synthesis of storage protein in cotyledons of soybean (Glycine max L. cv. Elf) in culture. No major discrimination in the incorporation of the amide or amino nitrogens of glutamine into protein is apparent, but the same nitrogens of asparagine are used with a degree of specificity. During the first seven days in culture with asparagine as the sole nitrogen source, the amino nitrogen donates approximately twice as much nitrogen to protein as does the amide nitrogen. The use of the amide nitrogen increases with longer periods of culture. The reduced use of the amide nitrogen was confirmed by its early appearance as ammonium in the culture medium. The amide nitrogen of asparagine was found at all times to be an essential precursor for protein because of its appearance in protein in residues whose nitrogens were not supplied by the amino nitrogen. In addition, methionine sulfoximine inhibited growth completely on asparagine, indicating that some ammonium assimilation is essential for storage protein synthesis. These results indicate that in a developing cotyledon, a transaminase reaction is of major importance in the utilization of asparagine for synthesis of storage protein and that, at least in the early stages of cotyledon development, reduced activities of ammonium-assimilating enzymes in the cotyledon tissue or in other tissues of the seed or pod may be a limiting factor in the use of asparagine-amide nitrogen.

Journal Article↗
PubMed1985

Effects of Nitrate Application on Amaranthus powellii Wats. : III. Optimal Allocation of Leaf Nitrogen for Photosynthesis and Stomatal Conductance.

Optimal allocation of leaf nitrogen maximizes daily CO(2) assimilation for a given leaf nitrogen concentration. According to the hypothesis of optimization, this condition occurs when the partial derivative of assimilation rate with respect to leaf nitrogen concentration is constant. This hypothesis predicts a linear increase of assimilation rate with leaf nitrogen concentration under constant conditions. Plants of Amaranthus powellii Wats. were grown at 1, 5, 10, or 45 millimolar nitrate to obtain leaves with different nitrogen concentrations. Assimilation rate at 340 microbar CO(2)/bar, stomatal conductance, CO(2)- and light-saturated net photosynthetic rate, the initial slope of the CO(2) response of photosynthesis, ribulose-1,5'-bisphosphate carboxylase activity, and phosphoenolpyruvate carboxylase activity were linearly related to estimated or actual leaf nitrogen concentration. The data are consistent with the optimal use of leaf nitrogen. This hypothesis and the hypothesis of optimal stomatal conductance were combined to determine the relationship between conductance and leaf nitrogen concentration. The slope of conductance versus leaf nitrogen concentration was not significantly different than the slope predicted by the combination of the two hypotheses. Stomatal conductance was linearly related to leaf nitrogen in the field and the slope decreased with lower xylem pressure potentials in a manner consistent with the hypotheses. Finally, apparent maximum stomatal aperture of isolated abaxial epidermal strips was linearly related to leaf nitrogen suggesting stomatal conductance and assimilation rate are controlled in parallel by leaf nitrogen concentration or some factor correlated with leaf nitrogen.

Journal Article↗
PubMed1984

[Effect of guar flour on endogenous nitrogen excretion in rats determined by the 15N-tracer technic].

The metabolic fecal nitrogen was determined in 8 young rats (90-100 g body weight) using a single oral dose of 75 mg 15N-glycine. Four rats were fed a diet containing 8% guar and 4 rats received a control diet without guar. Compared to the control group, apparent protein digestibility and nitrogen balance were significantly lower in the guar group. After an initial steep rise the 15N-elimination in feces and urine (days 2-8 after 15N-glycine application) followed an exponential curve in at least 2 phases, with increasing half-time values. The proportion of metabolic fecal nitrogen to total fecal nitrogen was calculated from the 15N-atom-% excess, determined daily in urine and in feces. This calculation is based on the assumption that the specific 15N-activity (15N-atom-% excess) in urine represents the specific 15N-activity of the endogenous nitrogen pool. The addition of guar raised the proportion of metabolic fecal nitrogen from 51% (control) to 73%, corresponding to an increase in total fecal nitrogen loss (24 mg) observed in the guar-fed animals. This indicates that the rise in fecal nitrogen loss caused by guar is due almost entirely to enhanced secretion of endogenous nitrogen and not to undigested food protein. Based on the analysis of 2,6-diamino-pimelic acid in the feces of 4 rats the proportion of bacterial nitrogen in the feces was calculated. It amounted to 19.8% of total fecal N in the control group, and to 30.1% in the guar group, or to 39.4% and 44.4% of metabolic fecal nitrogen respectively. Obviously the increased dietary fiber intake also caused a rise in the amount of metabolic fecal nitrogen, which is derived from gastro-intestinal secretions and epithelial tissue.

Animals↗
PubMed2001

Phosphorus limitation of nitrogen fixation by Trichodesmium in the central Atlantic Ocean.

Marine fixation of atmospheric nitrogen is believed to be an important source of biologically useful nitrogen to ocean surface waters, stimulating productivity of phytoplankton and so influencing the global carbon cycle. The majority of nitrogen fixation in tropical waters is carried out by the marine cyanobacterium Trichodesmium, which supplies more than half of the new nitrogen used for primary production. Although the factors controlling marine nitrogen fixation remain poorly understood, it has been thought that nitrogen fixation is limited by iron availability in the ocean. This was inferred from the high iron requirement estimated for growth of nitrogen fixing organisms and the higher apparent densities of Trichodesmium where aeolian iron inputs are plentiful. Here we report that nitrogen fixation rates in the central Atlantic appear to be independent of both dissolved iron levels in sea water and iron content in Trichodesmium colonies. Nitrogen fixation was, instead, highly correlated to the phosphorus content of Trichodesmium and was enhanced at higher irradiance. Furthermore, our calculations suggest that the structural iron requirement for the growth of nitrogen-fixing organisms is much lower than previously calculated. Although iron deficiency could still potentially limit growth of nitrogen-fixing organisms in regions of low iron availability-for example, in the subtropical North Pacific Ocean-our observations suggest that marine nitrogen fixation is not solely regulated by iron supply.

Atlantic Ocean↗
PubMed1990

Nitrogen-deregulated mutants of Phanerochaete chrysosporium--a lignin-degrading basidiomycete.

Two nitrogen-deregulated mutants of Phanerochaete chrysosporium, der8-2 and der8-5, were isolated by subjecting wild type conidia to gamma irradiation, plating on Poly-R medium containing high levels of nitrogen, and identifying colonies that are able to decolorize Poly-R. The mutants showed high levels of ligninolytic activity (14C-synthetic lignin----14CO2), and lignin peroxidase, manganese peroxidase and glucose oxidase activities in both low nitrogen (2.4 mM) and high nitrogen (24 mM) media. The wild type on the other hand displayed these activities in low nitrogen medium but showed little or no activities in high nitrogen medium. Fast protein liquid chromatographic analyses showed that the wild type as well as the der mutants produce three major lignin peroxidase peaks (designated L1, L2 and L3) with lignin peroxidase activity in low nitrogen medium. Furthermore, in low nitrogen medium, mutant der8-5 produced up to fourfold greater lignin peroxidase activity than that produced by the wild type. In high nitrogen medium, the wild type produced no detectable lignin peroxidase peaks whereas the mutants produced peaks L1 and L2, but not L3, and a new lignin peroxidase protein peak designated LN. Mutants der8-2 and der8-5 also produced high levels of glucose oxidase, an enzyme known to be associated with secondary metabolism and an important source of H2O2 in ligninolytic cultures, both in low and high nitrogen media. In contrast, the wild type produced high levels of glucose oxidase in low nitrogen medium and only trace amounts of this enzyme in high nitrogen medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Basidiomycota↗
PubMed2004

Nitrogen and oxygen mixture adsorption on carbon nanotube bundles from molecular simulation.

The adsorption of a nitrogen and oxygen mixture (air) on two types of single-walled carbon nanotube bundles at both sub- and supercritical temperatures is studied using grand canonical Monte Carlo molecular simulation. On an infinite periodic hexagonal bundle without an external surface, adsorption at a subcritical temperature is of type I. With increasing pressure, nitrogen adsorption first increases and then decreases until saturation; oxygen adsorption continues increasing, displacing nitrogen, until saturation. Both nitrogen and oxygen first form annuli inside the nanotubes, then with increased coverage they occupy the nanotube centers, and at the highest coverage some oxygen also adsorbs in the interstitial channels between the nanotubes. The selectivity of nitrogen over oxygen decreases with increasing pressure and reaches a constant near saturation. Adsorption at a supercritical temperature is also of type I, with both nitrogen and oxygen adsorption increasing with increasing pressure, though the selectivity of nitrogen to oxygen first increases slightly and then decreases with increasing pressure. On a small isolated hexagonal bundle with an external surface, adsorption at a subcritical temperature is of type II. With increasing pressure, nitrogen adsorption first increases, then decreases, and finally increases again due to wetting by liquid air, while oxygen adsorption increases continually. Both nitrogen and oxygen adsorb first at the internal annuli and at the grooves, and with increasing pressure, they then adsorb at the ridges and at the nanotube centers; at higher pressures, only oxygen adsorbs in the interstitial channels, and multilayer adsorption and wetting occur on the external surface as the bulk phase approaches saturation. The selectivity, like that of subcritical temperature adsorption on the infinite periodic bundle, decreases with increasing pressure and reaches a constant upon wetting. Adsorption at a supercritical temperature is of type I, with both nitrogen and oxygen adsorption increasing with increasing pressure. The selectivity of nitrogen to oxygen, like that of supercritical temperature adsorption on the infinite periodic bundle, first increases slightly and then decreases with increasing pressure. These results indicate that the adsorption selectivity strongly depends on temperature but only weakly depends on the type of the bundle and that a nitrogen--oxygen mixture (air) might be separated by competitive adsorption on the carbon nanotube bundles.

Adsorption↗
PubMedDate not supplied

Nitrogen export from an agriculture watershed in the Taihu Lake area, China.

Temporal changes in nitrogen concentrations and stream discharge, as well as sediment and nitrogen losses from erosion plots with different land uses, were studied in an agricultural watershed in the Taihu Lake area in eastern China. The highest overland runoff loads and nitrogen losses were measured under the upland at a convergent footslope. Much higher runoff, sediment and nitrogen losses were observed under upland cropping and vegetable fields than that under chestnut orchard and bamboo forest. Sediment associated nitrogen losses accounted for 8-43.5% of total nitrogen export via overland runoff. N lost in dissolved inorganic nitrogen forms (NO(3-)-N + NH4+-N) accounted for less than 50% of total water associated nitrogen export. Agricultural practices and weather-driven fluctuation in discharge were main reasons for the temporal variations in nutrient losses via stream discharge. Significant correlation between the total nitrogen concentration and stream discharge load was observed. Simple regression models could give satisfactory results for prediction of the total nitrogen concentrations in stream water and can be used for better quantifying nitrogen losses from arable land. Nitrogen losses from the studied watershed via stream discharge during rice season in the year 2002 were estimated to be 10.5 kg N/ha using these simple models.

Agriculture↗
PubMed1977

Effects of oral neomycin and kanamycin in chronic uremic patients: II. Nitrogen balance.

Nitrogen balance was studied for five to seven days before and during oral administration of neomycin or kanamycin to 14 patients with severe chronic renal failure who were receiving long-term nutritional therapy consisting of protein restriction and supplements of essential amino acids or their nitrogen-free analogues. There was a significant improvement in nitrogen balance during the antibiotic period when compared to the control period, averaging +0.80 g of N per day (P less than 0.005). There was no significant change in average dietary nitrogen, fecal nitrogen, the excretion of non-urea urinary nitrogen, or urea appearance (defined as the sum of urinary urea and the change in the urea pool) during the antibiotic period. However, total nitrogen intake increased by 0.47 g per day owing to nitrogen contained in the drugs. The lack of a change in fecal nitrogen implies that fecal nitrogen not attributable to the drug must have fallen substantially. We conclude that oral neomycin and kanamycin may improve nitrogen balance in patients with severe chronic renal failure by diminishing endogenous fecal nitrogen.

Administration, Oral↗
PubMed2001

Estimation of wet, dry and bulk deposition of atmospheric nitrogen in Connecticut.

Atmospheric nitrogen species including NO3-, NH4+ and total nitrogen in air and precipitation samples were collected with low-volume filter packs and wet deposition collectors from March 1999 through the end of December 2000 in seven sampling locations in Connecticut. Three sampling locations were chosen along the shores of Long Island Sound and four were chosen in interior sections of Connecticut. Sampling sites were chosen to represent both rural and urban sectors. Wet deposition flux of nitrogen species was calculated using wet concentrations, the volume of collected precipitation and the opening surface area of the Aerochemetrics wet deposition collector. The dry deposition flux of nitrogen species was estimated with the application of the dry deposition inferential model (DDIM). Bulk deposition of nitrogen was collected with the aid of a device based on the Swedish IVL Sampler. The dry deposition fluxes of NO3-, NH4+ and total nitrogen were found to be significantly higher in urban areas than the rural sampling locations. There was, however, no significant difference between the wet deposition fluxes of different nitrogen species in rural and urban sampling locations. When inland and coastal sites were compared, the dry deposition fluxes of NH4+ and total nitrogen were significantly higher in inland locations and there was no significant difference between coastal and inland sampling locations for wet deposition fluxes of nitrogen species. No significant difference was observed between the bulk deposition and the sum of the wet and dry deposition fluxes of total nitrogen at rural sampling locations. In urban sampling locations, the bulk deposition flux of total nitrogen was significantly lower than the sum of dry and wet deposition fluxes. There appears to be a similar seasonal trend in wet and dry deposition fluxes of total nitrogen in Connecticut with high and low deposition fluxes occurring in summer and winter periods, respectively.

Air Pollutants↗
PubMedDate not supplied

Nitrogen requirements of an old world nectarivore, the orange-tufted sunbird Nectarinia osea.

Nectarivorous birds are represented by three major radiations: honeyeaters and sunbirds in the Old World and hummingbirds in the New World. Costa's hummingbirds and New Holland honeyeaters have unusually low nitrogen requirements, which have been related to the species' low-protein, high-sugar diets. Therefore, we hypothesised that orange-tufted sunbirds (Nectarinia osea) would likewise have low-maintenance nitrogen requirements and low rates of endogenous nitrogen loss. To test this hypothesis, we measured nitrogen balance, total endogenous nitrogen loss, and body mass changes in captive birds, using insects as a nitrogen source. Nitrogen balance, estimated by regression analysis to be 3.9 mg d(-1), was less than one-half of that allometrically predicted, while total endogenous nitrogen loss (1.9+/-0.6 mg d(-1)) was less than one-third of the allometrically predicted value. Thus, orange-tufted sunbirds follow the same pattern of low nitrogen requirements found in hummingbirds and honeyeaters. Total endogenous losses of nitrogen in nectarivores are low because a fibreless, easily digestible liquid diet reduces nitrogen losses in the feces, while the protein-sparing effect of a diet containing largely sugar leads to low endogenous urinary nitrogen losses.

Animals↗