Reflectance measurement kidney

Both prerenal factors (dehydration, blood loss, altered vasomotor tone, age-related decreases in renal blood flow in rats) and postrenal factors (obstruction or extravasation of urine to the peritoneal cavity) may cause elevations of the commonly measured analytes that do not reflect primary kidney injury. Plasma analytes also cannot be used to determine the location of renal injury (glomerular versus tubular, or tubular segment affected) (Baum et al. 1975 Corman and Michel 1987 Finco 1997 Newman and Price 1999). 

It is contended that the renal slice technique measures primarily basolateral uptake of substrates or nephrotoxins, based on histological evidence of collapsed tubular lumens. This results in the inaccessibility of brush-border surfaces for reabsorptive transport (Burg and Orloff, 1969 Cohen and Kamm, 1976). This observation limits the ability of this model to accurately reflect reactions to nephrotoxins that occur as the result of brush-border accumulation of an injurious agent. Ultrastructurally, a number of alterations, particularly in the plasma membrane and mitochondrial compartments, have been shown to occur over a 2-h incubation period (Martel-Pelletier et al., 1977). This deterioration in morphology is very likely a consequence of the insufficient diffusion of oxygen, metabolic substrates, and waste products in the innermost regions of the kidney slice (Cohen and Kamm, 1976). Such factors also limit the use of slices in studying renal metabolism and transport functions. 

Surface fluorescence of NADH/NADPH can be recorded continuously with a DC fluorimeter and correlated with changes in experimental conditions. A mercury arc lamp (with a 340-375 nm filter in front) is used as a hght source for fluorescence excitation. The fluorescence response of reduced NADH/NADPH was measured at 450-510 nm. The DC fluorimeter and the Hg arc lamp are connected to the kidney by a trifurcated fiber optics light guide. NADH/NADPH fluorescence emission can be corrected for changes in tissue opacity by a 1 1 subtraction of reflectance changes at 340-375 nm from the fluorescence. To determine NADH/NADPH redox state of the total surface area of kidney cortex and to evaluate whether certain areas were insufficiently perfused, fluorescence photographs of the total surface area were taken. The study demonstrated that the surface fluorescence method is simple and provides specific information about the mitochondrial oxidation-reduction state. 

In molluscs the kidney was the only organ with measurable amounts of chromium. The level rose in molluscs selected for experimentation and exposed to chromium, but the levels were variable between organisms and different populations. This trend may reflect seasonal differences such as those observed by Bryan47, who suggested that variations in the concentrations of several elements in Chlamys opercularis and Pecten maximumus were due to changes in the availability of food. 

Kidney Stones. About one in five patients with clinical gout also has urinary tract uric acid stones. Although plasma and urinary uric acid should he measured in stone formers, many uric acid stone formers do not demonstrate either hyperuricuria or hyperuricemia. However, this may reflect the use of reference intervals derived in a purine-rich, westernized society.The etiology of uric acid stone formation also involves the passage of a persistently acid urine with loss... 

The pH of the plasma may be considered to be a function of two independent variables (1) the PCO2, which is regulated by the lungs and represents the acid component of the carbonic acid/bicarbonate buffer system, and (2) the concentration of titratable base (base excess or deficit, which is defined later), which is regulated by the kidneys. The plasma bicarbonate concentration is generally taken as a measure of the base excess or deficit in plasma and ECF, although it is recognized tliat conditions exist in which bicarbonate concentration may not accurately reflect the true base excess or deficit. 

It is recognized that GFR is dependent on numerous factors, one of which is protein load. Bosch suggested that an appropriate measure of renal function should reflect the filtration capacity of the kidney, and not the resting GFR. Subjects with normal renal function administered an oral or intravenous protein load prior to measurement of GFR have increased their GFR by as much as 50%. As renal function declines, the kidneys compensate by increasing SNGFR. The renal reserve, the maximal degree by which GFR can be increased, usually declines and thus may be a complementary measure of renal function for these patients. 

In 1958 Tallan et al. measured cystathionine levels in brain tissue from different species and found the remarkable pattern shown in Fig. 2, which appears to reflect an evolutionary trend. Cystathionine was approximately 3-fold higher in human vs. monkey, 10-fold higher vs. rat, and up to 40-fold higher than other species. A comparison with other human tissues showed that brain levels were about 40-fold higher than liver, kidney, or muscle. 

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