Nitrogenous waste

Numerous factors, many of them poorly understood, are involved in the development of HE. In severe hepatic disease, systemic circulation bypasses the liver, so many of the substances normally metabolized by the liver remain in the systemic circulation and accumulate to toxic levels. In excess, these metabolic by-products, especially nitrogenous waste, cause alterations in central nervous system functioning.20... 

Acute renal failure (ARF) is a potentially life-threatening clinical syndrome that occurs primarily in hospitalized patients and frequently complicates the course of the critically ill. It is characterized by a rapid decrease in glomerular filtration rate (GFR) and the resultant accumulation of nitrogenous waste products (e.g., creatinine and urea nitrogen), with or without a decrease in urine output. A recent consensus statement... 

Azotemia An excess of urea and other nitrogenous wastes in the blood as a result of kidney insufficiency. 

Gupta, S.K. and Sharma, R., Biological oxidation of high strength nitrogenous waste-water, Water Res.,... 

Liver takes carbon and nitrogen waste from muscle (alanine), disposes of the nitrogen, and recycles the carbon into glucose. 

The alanine cycle accomplishes the same thing as the Cori cycle, except with an add-on feature (Fig. 17-11). Under conditions under which muscle is degrading protein (fasting, starvation, exhaustion), muscle must get rid of excess carbon waste (lactate and pyruvate) but also nitrogen waste from the metabolism of amino acids. Muscle (and other tissues) removes amino groups from amino acids by transamination with a 2-keto acid such as pyruvate (oxaloacetate is the other common 2-keto acid). 

Cooperation between liver and muscle allows muscle to get rid of nitrogen waste and recycle the carbon skeleton into glucose. 

Since insect fecal pellets contain both undigested food and nitrogenous waste products, Bhattacharya and Waldbauer (58) subtracted the urine content of the feces from the total weight of the fecal pellet. This provided better estimates of assimilation and conversion of assimilated food. Schmidt and Reese (57) noted that BCW larvae will feed upon their fecal pellets if no other food is available. Growth on fecal pellets is nearly as rapid as growth on diet, suggesting that much of the nutrient content of the diet is not assimilated. The result of fecal feeding on nutritional parameters is an overestimation of the AD and ECI and an underestimation of the ECD. 

Substantial shunting of portal venous blood into the systemic circulation through oesophageal varices and other systemic connexions, including those surgically established, restricts the hepatic clearance of nitrogenous waste products, and the formation of... 

Levinson et al. (1991) reported that a nitrogenous waste, guanine (2-amino-6-hydroxypurine), functioned as an aggregation pheromone of the flour mite Ac. siro, together with ammonia as a kairomone. However, because guanine is nonvolatile, it should probably be classified as an arrestant rather than an aggregation pheromone. 

Levinson, H. Z., Levinson, A. R. and Mueller, K. (1991). Functional adaptation of two nitrogenous waste products in evoking attraction and aggregation of flour mites (Acarus siro L.). Anzeigerfttr Schaedlingskunde Planzenschutz Umweltschutz 64 55-60. 

Metabolism of nitrogen in a patient with a deficiency in the urea cycle enzyme carbamoyl phosphate synthetase I. Treatment with phenylbutyrate converts nitrogenous waste to a form that can be excreted. 

Interest in pteridines began with Frederick G. Hopkins, who in 1891 started his investigation of the yellow and white pigments of butterflies. Almost 50 years and a million butterflies later, the structures of the two pigments, xanthopterin and leucopterin (Fig. 15-17), were established.339 These pigments are produced in such quantities as to suggest that their synthesis may be a means of deposition of nitrogenous wastes in dry form. 

Because of the importance of the urea cycle, the capacity to convert ornithine into arginine is obvious. Complete loss of the ability to produce ornithine (a catalyst or carrier in the urea cycle) would limit the organism s control over production of its nitrogen waste product. 

Figure 12.1 Schematic of a single nephron, the functional unit of the kidney. Microsolutes are filtered from blood cells in Bowman s capsules. As the filtrate passes towards the collection tubule most of the microsolutes and water are reabsorbed by a type of facilitated transport process. The fluid finally entering the collecting tubule contains the nitrogenous wastes from the body and is excreted as urine. There are about 1 million nephrons in the normal kidney [1]...

Uric acid, the major nitrogenous waste product of uricotelic organisms, is also formed in other organisms from the breakdown of purine bases. Gout is caused by the deposition of excess uric acid crystals in the joints. 

Uric acid (Fig. 6) is the main nitrogenous waste product of uricotelic organisms (reptiles, birds and insects), but is also formed in ureotelic organisms from the breakdown of the purine bases from DNA and RNA (see Topics FI and Gl). Some individuals have a high serum level of sodium urate (the predominant form of uric acid at neutral pH) which can lead to crystals of this compound being deposited in the joints and kidneys, a condition known as gout, a type of arthritis characterized by extremely painful joints. 

While the complete oxidations of fats and carbohydrates yield C02 + H20, the complete oxidation of amino acids yields C02 + H20 and as well as ammonia. Three fates of this so-called nitrogen waste product are common in animals it can be excreted into the outside medium (ammonotelism, which is common in many aquatic animals) it can be excreted as uric acid (uricotely, common in reptiles and birds) or, it can be excreted as urea (common... 

The kidneys excrete a variety of waste products produced by metabolism, including the nitrogenous wastes urea (from protein catabolism) and uric acid (from nucleic acid metabolism). The kidneys also excrete many drugs or their metabolites, in particular those that are hydrophilic, have a small volume of distribution and a low degree of protein binding. 

Kidney Currently, there are no kidney-specific leakage enzymes assayed in serum. Renal function is evaluated by assaying serum levels of nitrogenous wastes—blood urea nitrogen (BUN) and creatinine—and monitoring protein levels in the urine (indicator of glomerular damage). 

From the symptoms and examination of blood and urine, a diagnosis of chronic renal failure is made. Unfortunately, considerable kidney damage can occur, often over a period of years, before the patient notices the symptoms associated with chronic renal failure. As the amount of functioning kidney tissue decreases, blood electrolytes begin to change. At the same time, the ability of the kidney to excrete nitrogenous waste decreases and urea concentration in the blood rises (uraemia). The patient may remain symptom-free until the concentration of urea rises sufficiently to cause the nausea and vomiting Kevin has recently experienced. 

Walsh, P. J., Wang, Y., Campbell, C. E., De Boeck, G., and Wood, C. M. (2001). Patterns of nitrogenous waste excretion and giU urea transporter mRJSTA expression in several species of marine fish. Mar. Biol. 139, 839-844. 

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