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PubMed2005

Denitrification as a nitrogen removal mechanism in a Vermont peatland.

Atmospheric deposition of nitrogenous compounds to ombrotrophic peatlands (i.e., those that have peat layers higher than their surroundings and receive nutrients and minerals exclusively by precipitation) has the potential to significantly alter ecosystem functioning. This study utilized the acetylene inhibition technique to estimate the relative importance of denitrification in nitrogen removal from a primarily ombrotrophic peatland, in an attempt to estimate the threat of increased nitrogen loadings to these areas. Estimates of mean rates of denitrification ranged from -2.76 to 84.0 ng N(2)O-N cm(-3) h(-1) (equivalent to -150 to 4800 microg N(2)O-N m(-2) h(-1)) using an ex situ core technique and from -8.30 to 5.98 microg N(2)O-N m(-2) h(-1) using an in situ chamber technique. Core rates may have been elevated over natural field levels due to effects of disturbance on substrate availability, and chamber rates may have been low due to diffusional constraints on acetylene and N(2)O. Net nitrification was also measured in an attempt to evaluate this process as a source of nitrate for denitrifiers. The low rates of net nitrification measured, in combination with the low rates of in situ denitrification and the very low amounts of free nitrate measured in this peatland, suggests that inorganic N turnover in this wetland is low. Results showed that nitrate was a limiting factor for denitrification in this peatland, with mean rates from nitrate-amended cores ranging from 13.1 to 260 ng N(2)O-N cm(-3) h(-1), and it is expected that increases in nitrogen loadings will increase denitrification rates in this ecosystem.

Acetylene↗
PubMed2001

Trichosporon porosum comb. nov., an anamorphic basidiomycetous yeast inhabiting soil, related to the loubieri/laibachii group of species that assimilate hemicelluloses and phenolic compounds.

Several isolates representing the genus Trichosporon were collected over a 6-year period from soils in The Netherlands. Based on classical growth tests with carbon and nitrogen compounds these were identical. Three of these (CBS 8396, CBS 8397 and CBS 8522) were subjected to molecular analysis of the D1/D2 region of the large subunit of rDNA. This confirmed that the three strains were identical, yet distinct from other members of the genus. Conspecificity was demonstrated with the type strain (CBS 2040) of Apiotrichum porosum Stautz (1931), with the exception that A. porosum, which had been isolated from exudate of a yew tree, differed morphologically from the soil strains. Based on the identity of DNA base sequences, morphology was not considered to be an adequate parameter to separate otherwise identical strains into two genera. Therefore, the new combination Trichosporon porosum is presented. Based on molecular sequence analysis, T. porosum may be related to T. sporotrichoides, within a weakly related clade that includes species such as Trichosporon laibachii and Trichosporon loubieri. The strains of T. porosum degrade phenolic compounds and hemicelluloses, which are characteristics with potential ecological importance in soil habitats. Characters distinguishing the nine species of the laibachii/loubieri group of species were listed. These include traditionally used tests as well as assimilation patterns of some aliphatic and phenolic compounds. Based on these tests, species such as Trichosporon multisporum and T. laibachii could be separated.

DNA, Fungal↗
PubMed1989

Absorption by the cecum of wild birds: is there interspecific variation.

The major functions proposed for the avian cecum--energy balance and osmoregulation--involve absorption of material from the cecum, yet little is known of these absorptive processes in wild birds. The magnitude of transport of compounds from the ceca depends on the concentrations of compounds in the ceca, the presence of transport pathways for those compounds, and the size of the reabsorptive surface. Interspecific variation in size of avian ceca is well documented, but the other two determinants of absorption are much less well studied. All ceca examined contained acetic, propionic, and butyric acid; water content varies from less than 70 to greater than 90%. Most other constituents have been quantified in just one or two species. A model for cecal transport, derived from studies of mammalian ceca but consistent with observations on birds, is described. A luminal (mucosal) Na+/H+ exchanger couples the absorption of Na+ to that of volatile fatty acids, which are absorbed in their uncharged (protonated) form; these two compounds are thereby mutually stimulatory in their absorption. The cecum also absorbs water, sodium, carbon dioxide, and probably some nitrogenous compounds (e.g., ammonia). Too few data exist to analyze interspecific variation in cecal transport in birds. However, variations in the following characteristics do exist: cecal contents, cecal absorptive surface area, transport characteristics of other regions of avian intestine (e.g., rectum), cecal transport among mammalian species, and histology of avian ceca. Studies of the physiological consequences of these variation should yield insight into the function and contributions of the avian cecum.

Absorption↗
PubMed1989

Biological nitrogen fixation under primordial Martian partial pressures of dinitrogen.

Early Earth and early Mars were similar enough such that past geochemical and climatic conditions on Mars may have also been favorable for the origin of life. However, one of the most striking differences between the two planets was the low partial pressure of dinitrogen (pN2) on early Mars (18 mb). On Earth, nitrogen is a key biological element and in many ecosystems the low availability of fixed nitrogen compounds is the main factor limiting growth. Biological fixation of dinitrogen on Earth is a crucial source of fixed nitrogen. Could the low availability of dinitrogen in the primordial Martian atmosphere have prevented the existence, or evolution of Martian microbiota? Azotobacter vinelandii and Azomonas agilis were grown in nitrogen free synthetic medium under various partial pressures of dinitrogen ranging from 780-0 mb (total atmosphere=1 bar). Below 400 mb the biomass, cell number, and growth rate decreased with decreasing pN2. Both microorganisms were capable of growth at a pN2 as low as 5 mb, but no growth was observed at a pN2 < or = 1 mb. The data appear to indicate that biological nitrogen fixation could have occurred on primordial Mars (pN2=18 mb) making it possible for a biotic system to have played a role in the Martian nitrogen cycle. It is possible that nitrogen may have played a key role in the early evolution of life on Mars, and that later a lack of available nitrogen on that planet (currently, pN2=0.2 mb) may have been involved in its subsequent extinction.

Atmosphere↗
PubMed1999

Temporal and spatial variations of airborne Mg, Cl, Na, Ca and K in rural areas of Norway

The Norwegian air chemistry monitoring network includes measurements of gaseous and particulate compounds in air at 12 rural sites. The sampling method is designed to determine concentration levels of sulphur and nitrogen compounds and uses a three-stage filter pack sampler. Concentration levels of base-cations and sea salts may also be determined from the chemical analysis of the filter extracts. In this study, concentration levels of water soluble Mg, Cl, Na, Ca and K in air have been investigated in terms of temporal, seasonal and spatial trends during the period 1986-1996. The results have been combined with precipitation chemistry data to estimate total deposition, and to evaluate the relative importance of dry deposition. While Na, Cl and Mg are of marine origin, which is clearly reflected in concentration ratios and spatial gradients, Ca and K are of a mixed origin. Air trajectory analyses indicate that air masses originating in Eastern Europe result in significantly higher airborne concentrations of non-sea salt Ca and K, than air from other sectors. Major sources of airborne Ca and K in Norway are expected to be of anthropogenic origin from combustion plants and industrial processes in Eastern Europe, while aeolian dust from agricultural areas within Europe or from Sahara is of limited importance. Concentration levels of non-sea salt base-cations in air were 20-30% lower during the 1990s, compared to 1986-1989. Precipitation chemistry data available since the early 1980s indicate even larger reductions, and in the order of 50%. Total deposition of non-sea salt base-cations during 1993-1996 was generally below 10 mmol(c) m-2 year-1, whereas in coastal areas with large precipitation amounts, inputs exceeding 15 mmol(c) m-2 year-1 occurred. Deposition of base-cations may thus counteract up to 25% of the strong acid anion input, but more typically in the order of 5-10%. Dry deposition of non-sea salt base-cations of southern Norway is comparatively small, typically contributing 10-30% to the total deposition in the inland areas, and relatively less in other regions.

Journal Article↗
PubMedDate not supplied

Health risk assessment of urban suspended particulate matter with special reference to polycyclic aromatic hydrocarbons: a review.

Airborne suspended particulate matter is an important marker of air quality. The term 'particulates' includes organic and inorganic matter, nitrogen compounds, sulphur compounds, polycyclic aromatic hydrocarbons (PAHs), several heavy metals, and radionuclides. The health risks from the 'classic' pollutants sulfur dioxide, nitrogen dioxide, ozone, carbon monoxide, and particulates have been comprehensively reviewed. Alarming levels of non-classic pollutants like the PAHs have been reported globally. PAHs have been found in placental tissues of women and in umbilical cord blood samples from newborn babies. The damaged DNA in cord blood is a indication of the fate of these pollutants in the environment. Hence, a need exists for a comprehensive investigation of the human health-related aspects of exposure to particulates and PAHs in the urban environment. This paper reviews the literature on PAHs in conjunction with particulate matter on a global perspective.

Adult↗
PubMed1975

A model for gastric cancer epidemiology.

It is postulated that one major subtype of gastric carcinoma ("intestinal type") is the end- result of a series of mutations and cell transformation begun in the first decade of life. The mutagen could be a nitroso compound synthesised in the upper gastrointestinal tract by the action of nitrite (i.e., from food or saliva) on naturally occurring nitrogen compounds. Under normal conditions these nitroso compounds do not reach the gastric epithelial cell, presumably because their synthesis is inhibited by antioxidants present in food or because of their inability to pass the mucous barrier. The barrier may be overcome by abrasives or irritants such as hard grains, food with high sodium-chloride concentration, or surfactants. Once the first mutation occurs, the glandular gastric epithelium is gradually changed to intestinal-type epithelium, the mucous barrier altered, and the pH elevated. Under these conditions, bacteria proliferate in the gastric cavity and facilitate the conversion of nitrates to nitrites, thereby increasing the nitrite pool and the probability of formation of mutagenic-carcinogenic nitroso compounds. This process of gastric atrophy and intestinal metaplasia goes on for 30 to 50 years until some of the individuals affected have the final mutation or cell transformation which allows the cell to become autonomous and invade other tissues.

Carcinogens↗
PubMed2005

Why isn't the N20 dodecahedron ideal for three-coordinate nitrogen?

Nitrogen molecules are the focus of much attention for their potential as high-energy density materials. The usefulness of such molecules as energy sources depends on the stability of the molecules with respect to dissociation. Many such molecules dissociate too easily to be a stable fuel, and the reasons for such instability are related to the details of structure and bonding of the molecule. Such details will be examined for isomers of the molecule N20. N20 has a highly symmetric isomer in which the 20 atoms occupy the vertexes of a dodecahedron. This isomer is a cage molecule in which all of the faces are regular pentagons that have interior angles of 108 degrees . These angles are very close to the known bond angles in very stable nitrogen compounds such as ammonia. Such a structure with only pentagons should provide an ideal bonding environment for three-coordinate nitrogen. However, by use of theoretical calculations including density-functional theory and fourth-order perturbation theory, along with the Dunning correlation-consistent basis sets, it will be shown that dodecahedral N20 is not the most stable cage for N20. The reasons why will be discussed in terms of the structure and bonding of the molecules.

Computer Simulation↗
PubMed1976

[Relations between atmospheric pollution and the respiratory tract].

After mentioning the close relationships between enviornmental pollution and the respiratory system, the various polluting compounds, from solid particles to fumes and gases, are reviewed, special attention being paid to the commonest types (sulphur and nitrogen compounds). Attention is called to two other polluting factors, asbestos and radioactivity, both of which are important in neoplastic pathology. The complexity of the air pollution problem in relation to respiratory pathology is stressed while stating that the most important problem remains that of prevention.

Air Pollutants↗
PubMed2006

Changes in carbon and nitrogen pool during in-situ aeration of old landfills under varying conditions.

Emissions from old landfills via leachate and the gas phase are influenced by state and stability of the organic matter in the solid waste and by environmental conditions within the landfill. Remediation of landfills by means of in-situ aeration is one possibility to reduce these emissions. By establishing aerobic conditions, biological processes in the landfill are accelerated. To investigate the effects of this remediation technology, lab-scale experiments with column tests have been carried out. The main goal of the present work is to characterize the changes of the carbon and nitrogen compounds in the aerated solid waste, the leachate and the gas phase under varying conditions. The results demonstrate a clear reduction of emissions and a stabilization of the organic matter. Furthermore, it is shown that both the intensity of aeration and the amount of water affect biological processes to a certain extent. Even when columns were operated under anaerobic conditions after a long running period of aeration, the emissions remained low.

Air Pollutants↗
PubMed2003

Biomarker responses and chemical analyses in fish indicate leakage of polycyclic aromatic hydrocarbons and other compounds from car tire rubber.

Rubber tire material contains toxic compounds including oils rich in polycyclic aromatic hydrocarbons (PAH), so-called highly aromatic (HA) oils, as well as other reactive additives used as antioxidants, antiozonants, and vulcanization accelerators. The toxicity of rubber tire leachates to aquatic organisms has been demonstrated before. However, previous studies have focused on lethal rather than sublethal effects. We kept rainbow trout (Oncorhynchus mykiss) in tanks with two types of tires: a tire containing HA oils in the tread or a tire free of HA oils in the tread. After 1 d of exposure, an induction of cytochrome P4501A1 (CYP1A1) was evident in both exposed groups, measured as elevated ethoxyresorufin-O-deethylase (EROD) activity and increased CYP1A1 mRNA levels. After two weeks of exposure, EROD activity and CYP1A1 mRNA were still high in fish exposed to leachate from HA oil-containing tire, whereas the effect was somewhat lower in fish exposed to leachate from HA oil-free tread tire. Compounds in the tire leachates also affected antioxidant parameters. Total glutathione concentration in liver as well as hepatic glutathione reductase, glutathione S-transferase, and glucose-6-phosphate dehydrogenase activities were markedly elevated after two weeks of exposure in both groups. The responses were greater in the group exposed to leachate from HA oil-free tread tire. Vitellogenin measurements did not indicate leakage of estrogenic compounds from the tires. Chemical analyses of bile from exposed fish revealed the presence of hydroxylated PAH as well as aromatic nitrogen compounds indicating uptake of these compounds by the fish.

Animals↗
PubMedDate not supplied

[Effect of various nitrogen sources on lipase formation by Rhizopus microsporus].

The effect of organic and mineral nitrogen sources on the production of lipolytic enzymes and the accumulation of biomass was studied with Rhizopus microsporus UzLT-I. Addition of mineral nitrogen sources to the growth medium weakly stimulated synthesis of lipase by the fungus. The production of lipolytic enzymes was highest on media with organic nitrogen compounds, particularly yeast autolysate and fodder yeast cells (0.1: 0.25%). The lipolytic activity of the cultural broth on media with these nitrogen sources increased by 50% cf. the control.

Culture Media↗
PubMed2002

Speciation of nitrogen - [N(3-)] and [N(2)(2-)] - in binary compounds.

The nitrogen content of the binary compounds SrN = Sr(4)[N](2)[N(2)], Sr[N(2)], and Ba[N(2)] (prepared by high-pressure syntheses) was determined analytically by using the carrier gas hot extraction method. For handling of the air- and moisture-sensitive samples, a transfer chamber was constructed to protect the compounds against decomposition before being analyzed. Additionally, it was necessary to develop a method allowing controlled and variable heating of the electrode furnace to get analytical results with high precision and accuracy. By means of a suitable temperature program it was possible not only to verify the existence but also to quantify the two different nitrogen species ([N(3-)] and [N(2)(2-)]), and thus confirm the results of recent neutron diffraction studies.

Journal Article↗
PubMed2006

Chemical characteristics and origins of nitrogen-containing organic compounds in PM2.5 aerosols in the Lower Fraser Valley.

Some nitrogen-containing organic compounds (NOCs) in PM2.5 aerosols in forest, tunnel, urban, rural, and mixed forest/ urban areas in the Lower Fraser Valley (LFV), British Columbia, Canada, were measured to assess their chemical characteristics, temporal and spatial distributions, and origins. The levels of E-caprolactam, isoindole-1,3-dione, benzothiazolone, and N-butyl-benzensulfonamide showed significant differences among the sites, with the highest level at the mixed forest/urban site, indicating that aerosols at this site were impacted by chemical manufacturing activities. N,N-diethyl-m-toluamide (deet) was detected at all locations but was highest in the forest area, demonstrating a widespread usage as an insect repellent in the LFV and at camps at the forest site. Alkyl amides, tracers from wood burning and cooking, ranging from C6 to C20 including two unsaturated amides, hexadecenamide, and 9-octa-decenamide, were detected at all sites. Three patterns of carbon number distributions of alkyl amides varied with location and time, and were mainly impacted by biomass burning or cooking compared to levoglucosan and cholesterol in the LFV. Ratio of oleamide to stearamide (C18:1/C18:0) was discussed as a potential indicator for determining "age" or transport range of biomass combustion plumes.

Air Pollutants↗
PubMed1995

Lipofuscin fluorophore inhibits lysosomal protein degradation and may cause early stages of macular degeneration.

One of the autofluorescent compounds that accumulates within the lipofuscin granules of the human retinal pigment epithelium (RPE) has now been identified as a quaternary nitrogen-containing cationic amphiphile (the bis-retinoid pyridinium salt, A2-E). Experimental evidence suggests that it may be responsible for lipofuscinogenesis in the RPE through its ability to inhibit lysosomal proteolysis. Furthermore, it may be involved in the events that trigger the changes leading to age-related macular degeneration (AMD), the leading cause of untreatable blindness in the elderly. It is suggested that if similar weakly basic nitrogenous compounds or cationic amphiphiles arise in reactions between amines and aldehydes in other tissues, a "self-assembling lysosomotropic amine" mechanism may provide an alternative explanation for lipofuscinogenesis those cell types as well.

Adolescent↗
PubMed2004

Performance of constructed wetland treating wastewater from seafood industry.

Wastewater from seafood industry contains high concentrations of organic matter, nitrogen compounds, and solid matter. Constructed wetland can be used as tertiary treatment and for nutrient recycling. This research studied the performance of nitrogen and suspended solids removal efficiency of a constructed wetland treating wastewater from a seafood-processing factory located at Songkhla, southern Thailand. The existing constructed wetland has dimensions of 85 m, 352 m and 1.5 m in width, length and depth respectively, with an area of about 29,920 m2. The water depth of 0.30 m is maintained in operation with plantation of cattails (Typha augustifolia). Flow rate of influent ranged between 500-4,660 m3/d. Average hydraulic retention time in the constructed wetland was about 4.8 days. Influent and effluent from the constructed wetland were collected once a week and analyzed for pH, temperature, dissolved oxygen (DO), biochemical oxygen demand (BOD5), Suspended solid (SS), total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3-N), organic nitrogen (Org-N), nitrate (NO3-N), and nitrite (NO2-N). The average removal efficiencies of BOD5, SS, TKN, NH3-N, and Org-N were 84%, 94%, 49%, 52% and 82%, respectively. It was found that the constructed wetland acting as a tertiary treatment process provided additional removal of BOD5, SS and TKN from wastewater from the seafood industry.

Biodegradation, Environmental↗
PubMedDate not supplied

[The nutritional status characteristics and the protein metabolic indices of children with acute leukemia].

The nutritive status features and the main parameters of nitrogen metabolism were investigated in 212 children with acute leukemia at varying stages of the disease. A study was made of the patients' body mass, nitrogen balance, excretion of nitrogenous compounds with urine and feces, total protein and albumin content in the blood, as well as blood content of urea, creatinine, amino nitrogen and uric acid. The results of the study have shown a negative influence of both leukemia and its therapy on the nutritive status of the patients, that was manifested in protein-energy deficiency and in protein assimilation disorders. A relationship has been revealed between infectious complications, preventing the successful treatment, and the nutritive status of the patients. Clarification of these pathogenetic mechanisms of the negative action of the disease itself and antileukemic therapy will help in the realization of the purposeful correction.

Acute Disease↗
PubMedDate not supplied

Influence of different cultural conditions on cellulase production by Nectria catalinensis.

The production of the extracellular cellulolytic enzyme system (endoglucanase, exoglucanase and cellobiase) of N. catalinensis was tested with different nitrogen sources, inorganic and organic ones, in liquid culture medium with microcrystalline cellulose. The nitrogen compounds used were: potassium nitrate, sodium nitrate, ammonium nitrate, ammonium phosphate, ammonium sulphate, ammonium chloride, ammonium carbonate, ammonium acetate, ammonium tartrate, urea, casamino acids, glycine, L-alanine, L-leucine, L-proline, L-lysine, L-aspartic acid, L-glutamic acid, L-asparagine, L-glutamine, L-phenylalanine, L-tyrosine, L-tryptophan, L-methionine and L-cysteine. Among these, ammonium nitrate and ammonium tartrate gave the highest yields of cellulases in 20-day-old cultures at a concentration equivalent to 0.75 g N/l in both cases. Optimal temperature for cellulase production, growth and cellulose degradation was 23 degrees C. On the other hand, an initial pH of 6.5 gave the highest yields of endoglucanase and cellobiase. In the same way, at pH 6.5, maximal growth and cellulose degradation were achieved. However, maximal exoglucanase production and glycogen content were reached at pH 7.5.

Amino Acids↗