Urine, composition concentration

The method used for the collection of luine to detect urinary solids is particularly sensitive to a variety of artifacts and variations in treatment (Cohen et al. 2007). Most of all, it is essential that the animals not be fasted or go without water during the period of collection of urine. Since the excretion of the substances that are included in formation of the urinary solids is dependent on their consmnption, fasting the animals changes the urine composition considerably and can lead to a condition in which the solids are no longer formed. Fiulhermore, urinary solids can be rapidly excreted in the mine and are not retained so if they are not being constantly formed anew, they will not be detected. This includes urinary tract calculi. Some calculi will be small enough that they will be excreted in the urine, or dissolve with the lowering of the concentration of the solute itself. Furthermore, many of these calculi are actually quite soluble in urine, such as uracil, and rapidly solubilize in the urine. 

To date, several small molecule biomarkers of renal toxicity have been described in the literature. Urine composition is considered to reflect kidney function and pathology. Thus, in the presence of proximal tubule damage, the relative concentrations of a number of metabolites (glucose, lactate, alanine, lysine, glutamine, glutamate, and valine) are markedly increased due to impaired reabsorption of those metabolites. An increase in the relative concentrations of those metabolites in urine is typically accompanied by a corresponding decrease in plasma levels [50,55],... 

The program utilized for this study provides the capability of establishing solution and solid phase equilibria for a multi-component system of up to thirty five components and 500 solution and solid species. Using equilibrium constant data for metals, Inorganic anions, and organic ligands (77) the iterative calculation provides for the determination of metal speciatlon as a function of pH and component concentration. Table I and II provide calculated constituent concentrations for the Purina rat chow used in the animal feeding studies for the basic urine composition. 

When considering how much urine to collect, one must decide whether to collect individual voids as discrete samples or to collect larger samples where the test subject voids several times in one collection vessel. If the researcher is interested in examining the analyte in the urine in each void, smaller 500-mL wide-mouthed jars can be used to collect each void over a 24-h period. These are generally referred to as spot void samples. Taking void spot samples in this manner allows the researcher to examine each void for the test analyte and also to composite a portion of each void into one 24-h sample in order to look at the overall concentration of the test analyte in the 24-h urine sample. If the spot samples are to be composited, aliquots of each spot sample should be removed based on each void s percentage of the total weight of the 24-h sample. The spot sample aliquots can be composited to form one 24-h sample. The leftover spot samples can be used to obtain individual void measurements of the analyte in question. 

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. 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

Hoey, L., Rowland, I.R., Lloyd, A.S., Clarke, D.B., and Wiseman, H., Influence of soya-based infant formula consumption on isoflavone and gut microflora metabolite concentrations in urine and on faecal microflora composition and metabolic activity in infants and children, Br. J. Nutr, 91, 607, 2004. 

An important condition to be fulfilled in order to use the method for detection of sweat formation and its composition is that the electrodes are elec-trolytically in contact with each other. This is not a strict condition for urine detection and as an early-warning system for diabetes, because in these applications a qualitative detection is enough, and therefore one can start with dry electrodes. For diagnosis of cystic fibrosis, this is not possible because here a quantitative detection of salt concentration is expected. Therefore, one needs to start from a system with electrodes that are elec-trolytically in contact with each other right from the start of the experiment. For this purpose, water is immobilised in high-density cotton in which the conductive stainless-steel yarn electrodes are implemented. 

Actions The loop diuretics act promptly, even among patients who have poor renal function or who have not responded to thiazides or other diuretics. Changes in the composition of the urine induced by loop diuretics are shown in Figure 23.6. [Note Loop diuretics increase the Ca++ content of urine, while thiazide diuretics (see p. 229) decrease the Ca++ concentration of the urine.] The loop diuretics cause decreased renal vascular resistance and increased renal blood flow. 

MS. After careful homogenization, the dried urine samples were analyzed directly by LA-ICP-MS without any time consuming digestion procedure. Matrix matched synthetic laboratory standards doped with Th (IRMM 60), uranium with natural isotope composition ( U/ U = 0.00725) and uranium isotope standard reference material (NIST U-930) at the low pgml level were prepared in order to smdy the figures of merit of the analytical methods developed. The recovery rate for thorium and uranium concentration measured on a synthetic urine laboratory standard by LA-ICP-MS varied between 91 and 104%. The precision and accuracy of the analytical methods was found to be 7 % and < 1 %, respectively, for uranium concentration, by using urine laboratory standards (at uranium concentration O.lngml. ... 

UV and carbohydrate chromatograms from urine (24-hour composites) and serum samples from clinically normal subjects are very similar. About three-fourths of the major peaks are common to all the normal subjects tested, and the concentrations (peak sizes) are within relatively narrow limits (e.g., see Fig. 18) (J2). Variation during the diurnal cycle is measurable but not prohibitive (Fig. 19), and variations during long periods of time are much less for one person than the variation from person to person (J2). 

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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