Methaemoglobin

Ramsay, D.H.E., and C.C.Harvey. 1959. Marking-ink poisoning An outbreak of methaemoglobin cyanosis in newborn babies. Lancet 1 910-912. 

Methaemoglobin forming compounds should be used cautiously in victims suffering from concurrent carbon monoxide poisoning or hypoxia. The second approach calls for provision of additional sulfur groups to enhance the detoxification of cyanide and thiocyanate by endogenous rhodanese this comes about by giving sodium thiosulphate. 

Methaemoglobin is formed in all red cells on a daily basis. Oxygen, being strongly electronegative, can abstract an electron from a donor to form a free radical ion called superoxide, 02 Fe2+ is just such a electron donor ... 

The enzymes GSH peroxidase, GSH reductase and SOD collaborate to ensure that the red cell is protected from the effects of methaemoglobin and superoxide. Disposal of hydrogen peroxide may occur by catalase, in a reaction which is also dependent on NADPH. This vital coenzyme is provided via the PPP. Although the PPP operates in all cell types for the provision of pentose sugars and nucleotides, its role in the RBC is more directed to cell survival than cell division. 

The scheme shown above, sometimes called the diaphorase reaction, is an important mechanism in the RBC for the reduction of methaemoglobin. A mechanistically... 

The number 1.34 is known as Huffiier s constant. It describes the volume of 02 (ml) that can combine with each 1 g Hb. In vitro, its value is 1.39 but this becomes 1.34 in vivo because abnormal forms of Hb such as carboxyhaemoglobin and methaemoglobin are less able to carry 02. 

Akintonwa DA. Theoretical mechanistic basis of oxidants of methaemoglobin formation. Med Hypotheses 2000 54 312. 

McLean S, Starmer GA, Thomas J Methaemoglobin formation by aromatic amines. J Pharmacol 21(7) 441-450, 1969... 

The potentially harmful effects of exposure to high concentrations of nitrates in drinking water result from reduction to nitrites, which combine with haemoglobin to form methaemoglobin (blue baby disease). Additionally, nitrosamine formation can cause cancer and hypertension. In nature, high levels of nutrients, such as nitrates, lead to eutrophication of water sources, which in, severe cases, lead to the extermination of the other aquatic life due the decreased levels of oxygen and luminosity. 

Methaemoglobin has very low affinity for oxygen, so large doses of nitrites can result in pseudocyanosis (reduced carrying capacity), tissue hypoxia and death. 

Based on the avidity of cobalt for cyanide ions, intravenous injection of the cobalt EDT A complex has been recommended as being the best antidote in cyanide poisoning73). Earlier therapy was based on sodium nitrite and sodium thiosulphate, with partial conversion of haemoglobin to methaemoglobin. 

Soldatov, A.A. and Maslova, M.N. (1989). Methaemoglobin concentration in fish blood over the annual cycle (In Russian). Zhumal Evolutionnoy Biokhimii i Physiologii 25,454-459. 

The history of ferredoxin is outlined in its simplest form in Table 1. Prior to the isolation of ferredoxin from Clostridium pasteurianum, proteins now known to be functionally similar to the ferredoxin from this organism had been isolated from photosynthetic cells and were designated by a variety of names in the belief that each name described the protein s true function. In 1952, Davenport, Hill, and Whatley (39) isolated a soluble factor from chloroplasts which, upon illumination with chloroplast fragments, catalyzed the reduction of methemoglobin. This factor, which they named the "methaemoglobin reducing factor , had the characte... 

Dinitrobenzene is a strong poison, affecting the blood and the liver. It causes the formation of methaemoglobin, which can be seen in the intense blue discol-ouration-cyanosis-of the lips, mucous membranes and the face of the victim. 

Compound II is highly toxic. It results in the formation of methaemoglobin. The presence of trinitrotoluene in the human body leads to an enhancement of the formation of glucuronic acid, which reacts with the alcohols V and VI to form the corresponding esters. 

Keilin D, Hartree EF (1951) Purification of horseradish peroxidase and comparison of its properties with those of catalase and methaemoglobin. Biochem J 49 88-106... 

Froslie A. 1971a. Methaemoglobin formation in vitro by 6-amino metabolites of DNOC and DNBP. Acta Pharmacol Toxicol (Copenh) 29 490-498. 

Haemoglobin is normally safely compartmentalised within the erythrocyte. It is highly susceptible to autoxidation. In the erythrocyte, there normally develops a balance between the spontaneous formation of methaemoglobin and superoxide radicals and the restoration of this oxidised haemoglobin to its normal functional state (Fig. 13 for a review see ref. [68]). 

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