Indicator dilution method

Crone C (1963) The permeability of capillaries in various organs as determined by use of the indicator dilution method. Acta Physiol Scand 58 292-305... 

Koscielniak, P., Kozak, J., Wieczorek, M. Calibration by the standard addition and indicative dilution method in flame atomic absorption spectrometry. J. Anal. At. Spectrom. 26, 1387-1392 (2011)... 

The indicator dilution method is a technique used to determine flow rates of fluids in channels for which devices like rotameters and orifice meters cannot be used (e.g., rivers, blood vessels, and large-diameter pipelines). A stream of an easily measured substance (the tracer) is injected into the channel at a known rate and the tracer concentration is measured at a point far enough downstream of the injection point for the tracer to be completely mixed with the flowing fluid. The larger the flow rate of the fluid, the lower the tracer concentration at the measurement point. 

A variation of the indicator dilution method (see preceding problem) is used to measure total blood volume. A known amount of a tracer is injected into the bloodstream and disperses uniformly throughout the circulatory system. A blood sample is then withdrawn, the tracer concentration in the sample is measured, and the measured concentration [which equals (tracer injected)/(total blood volume) if no tracer is lost through blood vessel walls] is used to determine the total blood volume. 

Meier, P. and K. Zieler, On the theory of the indicator-dilution method for measurement of blood flow and volume. J Appl Physiol, 1954. 6 p. 731-44. 

Zierler, K.L., Theoretical basis of indicator-dilution methods for measuring flow and volume. Circ Res, 1962. 10 p. 393-407. 

Introduction Indicator-Dilution Method Pick Method Ejection Fraction References... 

The principle underlying the indicator-dilution method is based on the upstream injection of a detectable indicator and on measuring the downstream concentration-time curve, which is called a dilution curve. The essential requirement is that the indicator mixes with all the blood flowing through the central mixing pool. Although the dilution curves in the outlet branches maybe shghtly different in shape, they all have the same area. 

Before describing the various indicator-dilution methods, it is useful to recognize that there are two types of indicators, diffusible and nondiffusible. A diffusible indicator will leak out of the capillaries. A nondiffusible indicator is retained in the vascular system for a time that depends on the type of indicator. Whether cardiac output is overestimated with a diffusible indicator depends on the location of the injection and measuring sites. Table 13.1 lists many of the indicators that have been used for measuring cardiac output and the types of detectors used to obtain the dilution curve. It is obvious that the indicator selected must be detectable and not alter the flow being measured. Importantly, the indicator must be nontoxic and sterile. 

Sherman, H. On the Theory of Indicator-Dilution Methods Under Varying Blood-Flow Conditions. Bull. Math. Biphysics 22 (1960) 417. 

Glycerol kinase activity can be measured directly or indirectly however, these assays are not available as a clinical test and are done exclusively on a research basis. The direct method is as has been described previously [4, 6] and is used in the isotope dilution method indicated above. The amount of protein and the incubation time vary between cell types and it is important to be within the linear range of the assay for the given cell type. The indirect methods involve incorporation of 14C from glycerol into macromolecules and its subsequent oxidation to 14C02 [7,11]. 

The hydrolytic behavior of both NaX and NaY as measured at 10 2ilf. NaCl by isotopic dilution methods has also been measured as a function of the zeolite content. The results, along with standard deviations from the mean, are summarized in Table II the figure in parenthesis indicates the... 

Figure 6.6. Sorption (solid lines) and desorption isotherms where O represents consecutive desorption method and indicates dilution desorption method for parathion and fensul-fothion sulfone in aqueous suspensions of an organic soil showing hysteresis, [From Bowman and Sans (1985), with permission.]...

The second item is the concentration of the reactant in the feed. We considered the case in which the feed is pure reactant A and found a heat removal rate for a given conversion and reactor temperature. However, suppose that the feed were a mixture of reactant A and product B. Now for the same feedrate and conversion, there is less of A to react so the heat transfer requirements are lower. This indicates one method of improving reactor controllability, which is to reduce reactant feed composition by diluting the feed with some nonreactive component. Of course, the downside of this approach is that there must be more material to recycle, which increases capital and energy costs. 

Diaza[12]coronand-4 (21) was condensed with diethylene glycol bismesylate 22 in the presence of butyllithium. Precipitation, occuring during the reaction course, afforded the proton cryptate 24 H+ c= [1.1.1] in 40% yield. It should be noted that [1.1.1] was obtained only in 10% yield via the high-dilution method 23). Lithium promoted cyclization was excluded (as an alternative mechanism) by an additional experiment in which KH served as a base instead of BuLi. Identical yield was achieved, indicating that intramolecular hydrogen bonding was responsible of the cyclization. 

Sensitivity testing usually is performed by a microbroth dilution method and should encompass all categories of antibiotics. Zones of inhibition around antibiotic-containing drugs indicate relative sensitivity.The agents to be tested may vary based on availabiUty of antibiotic discs, geographic prevalence rates of infection, or practitioner preference (Box 25-3). 

Fig. 1. The effect of hsp70 on the refolding of cAAT and pmAAT. Refolding of acid unfolded cAAT or pmAAT was performed by rapid dilution of the denatured enz3rmes in the refolding buffer to a final protein concentration of 1.8 pM. When present, hsp70 (1.8 pM) was added to the refolding buffer before initiation of the refolding reaction. After incubation for 120 min at 10 C, the transaminase activity recovered was measured as indicated under Methods. Reactivation data are expressed relative to that of the native enzyme incubated under identical conditions.

Double-tailed ester-type surfactants 6a-c, f, g and uronamides 10c, f, g were studied as to their properties as emulsifying agents. Three systems were studied sunflower oil-water, paraffin oil (Marcol 82)-water, and capric/caprylic triglycerides (Oleon)-water. In order to determine the w/o or o/w type of emulsions formed in the presence of the surfactants, the drop-dilution method was used. To a small portion of the emulsicMi (surfactant/water/oil 5/47.5/47.5 in weight) placed oti a slide, a drop of water with a pin point is added and stirred slightly. If the water blends with the emulsion, it is an oil-in-water emulsion, but if oil blends with the outside phase it is a water-in-oil emulsion. As indicated in Table 5, ester-type and amide-type compounds 6a-c and 10c, based on C8 to C12 fatty alcohols and amines, are able to form o/w emulsions whereas surfactants 6f, g and lOf, g composed of stearic (Cl8) or oleic (C18 l) alkyl chains exhibit w/o emulsions. 

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