Urine protein, composition

However, in spite of some gross similarities, the protein compositions of urine and serum differ markedly. The ratio of albumin to globulin, which varies from 1.3 to 3 in serum, is 0.5 in urine. A number of proteins normally found in serum are absent from urine (fibrinogen, ceruloplasmin, ai, a-, and j -lipo-proteins) a prealbumin, an ai-, a2-, and a y-globulin have been found in urine, but not in serum. 

Urine. The composition and the daily amount of urine depend on the intake of liquids. Data on the daily excretion of various substances, therefore, are always given on a 24-hour basis. Urea is the chief waste product. The excretion of N-con-taining compounds generally is of prime importance (carbon in food is largely exhaled as CO2). The amount of urea excreted can be correlated directly with the amount of protein catabolized 1 gm urea nitrogen = 6.25 gm protein. 

Experimental. A second study was conducted with nine postmenopausal women age 51-65 yr. The subjects were fed standardized meals for 19 weeks. The mean composition for the 7-day menus of natural foods as % of total calories was 15% protein, 50% carbohydrate, 35% fat with a P/S ratio of 0.7, 10 g/day crude fiber, and less than 300 mg/day cholesterol. In addition, the diets supplied 1289 mg calcium, 1832 mg phosphorus, 2561 mg sodium and 5099 mg potassium daily. The diets met the RDA for all other nutrients. Calorie levels were adjusted to maintain body weight. The experimental meals were fed during the last six weeks of this 19-week period. No more than one liquid meal was consumed by each subject in one week. Fasting and postprandial samples of blood and urine were collected as in the previous study. Diuresis was induced by scheduled consumption of water. 

The present communication is concerned with calcium balance studies carried out during the Intake of a variety of dietary factors including minerals and protein as well as drugs. The studies were performed In adult males under strictly controlled conditions in the Metabolic Research Unit. The diet was kept constant throughout the relatively long term studies and complete collections of urine and stool were obtained. The composition of this diet was previously described (5). The diet and the excretions in urine and stool were analyzed for calcium throughout the studies. These data formed the basis of calcium balances which were determined for several weeks. Calcium was analyzed by atomic absorption spectroscopy (6). 

Except for its lower protein concentration, glomerular filtrate at the top of the nephron is chemically identical to the plasma. The chemical composition of the urine is however quantitatively very different to that of plasma, the difference is due to the actions of the tubules. Cells of the proximal convoluted tubule (PCT) are responsible for bulk transfer and reclamation of most of the filtered water, sodium, amino acids and glucose (for example) whereas the distal convoluted tubule (DCT) and the collecting duct are concerned more with fine tuning the composition to suit the needs of the body. 

Unlike urine, plasma contains about 7% proteins and a substantial amount of lipids, salts, and enzymes, especially esterases. The pH of plasma is approximately 7.4. Despite its complex nature, plasma exhibits a composition that hardly varies within the animal species and the diet, except for the lipid content, which is diet-dependent. 

A number of procedures used to determine protein quality involve bioassays. Bioassays require feeding live animals protein ingredients for a specified period of time, and then estimating the nutritive value of the protein. Two such assays are the rat-based protein efficiency ratio (PER) bioassay and the human nitrogen balance assay (Dimes et al., 1994). Animal feeding experiments require chemical analyses of both the dietary inputs and then the metabolic output of the animal (e.g., body composition analysis, fecal sample analysis, collection, and assay for urine) from which the efficiency of protein metabolism can be predicted as well as how the protein supports animal growth and cell maintenance. 

Branched-Chain Oxo-acid Decarboxylase and Maple Syrup Urine Disease The third oxo-add dehydrogenase catalyzes the oxidative decarboxylation of the branched-chain oxo-acids that arise from the transamination of the branched-chain amino acids, leucine, isoleuctne, emd vtdine. It has a similEU subunit composition to pyruvate and 2-oxoglutarate dehydrogenases, and the E3 subunit (dihydrolipoyl dehydrogenase) is the stune protein as in the other two multienzyme complexes. Genetic lack of this enzyme causes maple syrup urine disease, so-called because the bremched-chain oxo-acids that are excreted in the urine have a smell reminiscent of maple syrup. 

The other biological fluid commonly assayed is mine. Unlike plasma or serum this contains only low concentrations of protein so protein removal is not necessary. The composition of urine varies widely and so does the volume passed by different individuals. Generally speaking large volumes are available for analysis. One of the major problems with urine is the large number of small organic compounds that are present. Liquid-liquid extraction (often preceded by conjugate hydrolysis) is often the sample preparation procedure used for urine analysis. 

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