Nitrite

About: Nitrite is a research topic. Over the lifetime, 15425 publications have been published within this topic receiving 484581 citations.

Dietary Nitrate Supplementation and Exercise Performance

Abstract: Dietary nitrate is growing in popularity as a sports nutrition supplement. This article reviews the evidence base for the potential of inorganic nitrate to enhance sports and exercise performance. Inorganic nitrate is present in numerous foodstuffs and is abundant in green leafy vegetables and beetroot. Following ingestion, nitrate is converted in the body to nitrite and stored and circulated in the blood. In conditions of low oxygen availability, nitrite can be converted into nitric oxide, which is known to play a number of important roles in vascular and metabolic control. Dietary nitrate supplementation increases plasma nitrite concentration and reduces resting blood pressure. Intriguingly, nitrate supplementation also reduces the oxygen cost of submaximal exercise and can, in some circumstances, enhance exercise tolerance and performance. The mechanisms that may be responsible for these effects are reviewed and practical guidelines for safe and efficacious dietary nitrate supplementation are provided.

A highly sensitive electrochemical sensor for nitrite detection based on Fe2O3 nanoparticles decorated reduced graphene oxide nanosheets

Abstract: Nitrite is one of the most frequent measurements in environmental analysis due to their detrimental effect on environment. The development of simple and sensitive analytical method for the detection of nitrite is highly important. In this study, we report the fabrication and testing of nitrite sensor based on the use of Fe 2 O 3 /rGO composite. The Fe 2 O 3 /rGO composites were prepared by a facile one-step hydrothermal approach. Field emission scanning electron microscope studies and powder X-ray diffraction analysis revealed that the Fe 2 O 3 nanoparticles were successfully grafted on the rGO nanosheets. Further, the prepared Fe 2 O 3 /rGO composites have been examined for the electrochemical detection of nitrite using cyclic voltammetry and differential pulse voltammetry techniques. The electrochemical studies demonstrated that Fe 2 O 3 /rGO composite detects nitrite linearly over a concentration range of 5.0 × 10 −8 to 7.8 × 10 −4 M with a detection limit of 1.5 × 10 −8 M. The obtained detection limit for Fe 2 O 3 /rGO composite is very much comparable to the recent literature values. Furthermore, the Fe 2 O 3 /rGO composite modified electrode showed an excellent anti-interference ability against electroactive species and metal ions.

Nitrous oxide production by Alcaligenes faecalis under transient and dynamic aerobic and anaerobic conditions

Abstract: Nitrous oxide can be a harmful by-product in nitrogen removal from wastewater. Since wastewater treatment systems operate under different aeration regimens, the influence of different oxygen concentrations and oxygen fluctuations on denitrification was studied. Continuous cultures of Alcaligenes faecalis TUD produced N2O under anaerobic as well as aerobic conditions. Below a dissolved oxygen concentration of 5% air saturation, the relatively highest N2O production was observed. Under these conditions, significant activities of nitrite reductase could be measured. After transition from aerobic to anaerobic conditions, there was insufficient nitrite reductase present to sustain growth and the culture began to wash out. After 20 h, nitrite reductase became detectable and the culture started to recover. Nitrous oxide reductase became measurable only after 27 h, suggesting sequential induction of the denitrification reductases, causing the transient accumulation of N2O. After transition from anaerobic conditions to aerobic conditions, nitrite reduction continued (at a lower rate) for several hours. N2O reduction appeared to stop immediately after the switch, indicating inhibition of nitrous oxide reductase, resulting in high N2O emissions (maximum, 1.4 mmol liter-1 h-1). The nitrite reductase was not inactivated by oxygen, but its synthesis was repressed. A half-life of 16 to 22 h for nitrite reductase under these conditions was calculated. In a dynamic aerobic-anaerobic culture of A. faecalis, a semisteady state in which most of the N2O production took place after the transition from anaerobic to aerobic conditions was obtained. The nitrite consumption rate in this culture was equal to that in an anaerobic culture (0.95 and 0.92 mmol liter-1 h-1, respectively), but the production of N2O was higher in the dynamic culture (28 and 26% of nitrite consumption, respectively).

Semiautomated Measurement of Nitrate in Biological Fluids

Abstract: The nitric oxide radical (NO·) plays an important role as a physiological messenger (1). NO is formed from l-arginine (2) by NO synthase (NOS; EC 1.14.13.39), which exists in several isoforms (3). Constitutive calcium-dependent isoforms (cNOS) modulate the control of vascular tone in endothelial cells or the neurotransmission in neurons, whereas inducible calcium-independent isoforms (iNOS) are located in macrophages, chondrocytes, and hepatocytes and are induced by cytokines and endotoxin (4)(5). Pathological conditions associated with increased release of cytokines and endotoxin, e.g., inflammation or sepsis (6), can therefore increase NO production. NO is a very unstable, short half-life gas that breaks down rapidly into the stable products nitrate and nitrite (7). Upon coming into the bloodstream, nitrite reacts immediately with oxyhemoglobin to form methemoglobin. Consequently, most NO produced is detected in serum as the remaining product, nitrate (8). Recently, several reports focused on methods to measure nitrate concentrations in biological fluids (9)(10)(11). One of the most commonly used methods is based on the reduction of nitrate to nitrite by cadmium or nitrate reductase, the nitrite produced being determined by Griess reaction (9)(12)(13). Other methods for monitoring NO production are based on chemiluminescence (11)(14), enzymatic assay with an internal standard (10), or chromatographic procedures (8) for nitrate (15)—all of which are time-consuming for routine application in clinical chemistry laboratories. We describe a rapid semiautomated method based on the Griess reaction, involving a shortened incubation period of nitrate with cadmium. The method is applicable to several types of biological fluids. Serum or plasma samples from healthy individuals after a 12-h fast were obtained in accordance with the Medical Ethical Committee of our hospital. Samples were stored at −20 °C and were stable for at least 6 months. The method was …