Ammonia

About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.

The ‘neurotoxicity’ of l-2,4-diaminobutyric acid

Abstract: The neurolathyrogen l-2,4-diaminobutyric acid is concentrated by liver, and liver damage can yield neurotoxicity; thus the neurotoxicity caused by this compound may be due to liver damage followed by secondary brain damage. 1. The intraperitoneal administration of toxic doses of l-2,4-diaminobutyric acid to rats resulted in hyperirritability, tremors and convulsions in 12–20hr. and increased the concentration of ammonia of blood and brain slightly and the concentration of glutamine of brain two- to three-fold. By contrast, toxic doses of l-homoarginine, l-lysine, l-leucine and ammonium acetate caused dyspnoea, extreme prostration, and in some cases coma in 15–30min., and increased the concentration of ammonia of blood significantly and the concentration of glutamine of brain slightly. These results indicate that l-2,4-diaminobutyric acid caused a chronic ammonia toxicity, whereas the other amino acids and ammonium acetate resulted in an acute ammonia toxicity. 2. Liver slices from l-2,4-diaminobutyric acid-treated animals and normal liver slices preincubated with l-2,4-diaminobutyric acid utilized ammonia and formed urea at a lower rate than control slices from normal rats. 3. l-2,4-Diaminobutyric acid inhibited competitively ornithine carbamoyltransferase of rat liver homogenates, thus demonstrating that this reaction is a primary site of toxicity for this neurolathyrogen. Although we were unable to show marked elevations of blood ammonia concentration after treatment with l-2,4-diaminobutyric acid, these results are interpreted to mean that ammonia utilization (urea synthesis) in liver is inhibited by l-2,4-diaminobutyric acid and that at least part of the neurotoxicity is due to a prolonged slight increase in body ammonia concentration.

Removal of Nutrients in Wastewater by using Magnesium Salts

Abstract: The removal of ammonia nitrogen and phosphorus from wastewater by precipitating out with magnesium salts was showed. Factors of pH, reaction time, N/P ratio, and dissolution test were investigated to find optimal conditions for magnesium ammonium phosphate (MAP) formation. The investigated conditions were also applied to toxic industrial wastewater. SEM and EDS analyses indicated that the precipitate was magnesium ammonium phosphate that was fine crystals of Mg and P compounds. The removal of ammonia and phosphorus increased with pH up to 10.5 where 82.6% and 97% of ammonia nitrogen and phosphorus were removed. It was found that minimum 10 minutes reaction was required for the nutrients removal. However, a small amount of phosphorus dissolved after 60 minutes. Ammonia nitrogen was well removed at one mole to two moles of magnesium. But at doses higher than two moles of magnesium, ammonia nitrogen increased due probably to the decreased pH. Bittern and sea water proved to be excellent coagulants for nutrie...

Soil Nitrogen Turnover — Mineralisation, Nitrification and Denitrification in European Forest Soils

Abstract: Mineralisation, nitrification and denitrification are major processes in the soil nitrogen cycle (see Schulze, Fig. 1.2, this Vol. Chap. 1). Nitrogen (N) mineralisation is by definition the biotic conversion of organic N into inorganic N, mainly NH4 + and NO3 −. Many organism groups, bacteria, fungi and certain soil animals, possess this capability, and the product formed is generally ammonia/ammonium, depending on the soil pH. Ammonium (NH4 +) can be oxidised via nitrite (NO2 − to nitrate (NO3 −. Both chemoautotrophic (using CO2 as a C source) and heterotrophic (using organic C as a C source) microorganisms can perform this nitrification process (Prosser 1986). Heterotrophic microorganisms can also produce nitrate directly from organic N sources (Killham 1986). Nitrate can be reduced via nitrite to nitric oxide (NO), nitrous oxide (N2O) and/or dinitrogen (N2) (denitrification). In addition to these processes, ammonium/ammonia, nitrite and nitrate can be assimilated (immobilised) by microorganisms, mycorrhizal fungi and roots. Further, ammonia and nitrite are known to react with certain organic compounds and, thus, be chemically immobilised (Nommik and Vahtras 1982; Azhar El Sayed et al. 1986).

Urea as a nitrogen source for the phytoplankton in the Oslofjord

Abstract: Ambient concentrations of urea in the inner Oslofjord, Norway, showed a pronounced yearly cycle in 1980, with values in the range 0.1 to 10.0 μg-at N l-1; this cycle resemble that of ammonia although urea concentrations were usually lower. The uptake of urea by phytoplankton was investigated using 15N. Urea was usually a less important N source than NH 4 + , and accounted for 0 to 53% (mean 19%) of summed NH 4 + +NO 3 - + urea uptake rates from April to October. Absolute as well as relative (specific) uptake rates of urea were higher in the summer (June–August) than at other times. Uptake of urea was inhibited by NH 4 + concentrations higher than 1 to 2 μg-at N l-1. The summed NH 4 + +NO 3 - + urea uptake rate was exponentially related to temperature.