Plasma equivalent units

Results from a substrate assay may be reported in several different ways. For example, six different ways to report the level of the thrombin inhibitor, antithrombin III, have been used (S25). One system fiimiliar to biochemists would be nanokatals (nkat) per unit of volume. A nkat is defined as the amount of enzyme which converts one nanomole of substrate per second. The second system, which would be more fiimiliar to the coagulationist, reports results in terms of percent of normal or plasma equivalent units (PEU), one PEU being the amount of a substance present in 1 ml of a standard laboratory plasma pool drawn from normal donors. This question on reporting units becomes more important when the substrate assays are substituted in the global assays, PT and PTT. The latter clot-endpoint tests measure the total effect of many fiictors and it is known that the PT and PTT are insensitive to changes in some of the fectors over a wide range, i.e., 60-120%. This point will be discussed later in Sections 6 and 7. 

Calcitonin. Calcitonin is available commercially from pork and salmon extracts (Calcimar, Armour) as well as by synthesis. Preparations are bioassayed on the basis of their calcium-lowering activity in comparison to the potency of pure pork calcitonin of which ca 4 p.g is equivalent to 1 MRC unit (Medical Research Council, U.K.). For clinical use, vials containing 400 units in 4 mL are available. The recommended daily dosage is 100 units to be adrninistered subcutaneously or intramuscularly because its plasma half-life is short (4—12 min). 

The reference standards are used to quantitate the standards that are employed in the kits to generate the standard curves. The kit standards are recombinant single-stranded DNA molecules that are added to either negative serum or plasma at known concentrations. Because the standard curve is not constructed with reference standards, Chiron initially chose to use the term equivalent to describe the units of nucleic acid quantitation in clinical samples. An equivalent was defined as the amount of nucleic acid in a clinical sample that gave a signal equal to one molecule of the reference standard nucleic acid. The term copy rather than equivalent is used to describe the units of nucleic acid quantitation in the HIV-1 bDNA assay. The terms are now used interchangeably. 

The equivalent of the tryptic fragment of human transferrin receptor has been expressed in Chinese hamster ovary cells and its structure determined at a resolution of 0.32 nm (Lawrence et ah, 1999). The asymmetric unit of the crystals contains four transferrin receptor dimers. Interpretable electron density is found for the entire tryptic fragment except for Arg-121 at the amino terminus, and density is also seen for the first N-acetylglucosamine residue at each of the N-glycosylation sites. The transferrin receptor monomer is made up of three distinct domains, organized such that the dimer is butterfly shaped (Figure 5.10, Plate 7). The likely orientation of the dimer with respect to the plasma membrane has been assigned on the basis of the... 

Equivalent to the volume of plasma completely cleared of drug per unit of time ... 

A correlation may be established between the concentration of oxidized lipids and the TEARS value, expressed as MDA equivalents, in uM units. Correction is due in some cases for the interference by dyes or other factors. For example, the presence of anthocyanins in red cabbage leaves or turbiditjf causes overestimation of lipid hydroperoxides in plant tissue by the TEARS method. TEARS was used to assert the level of endogenous peroxides in hypo- and hyperthyroidism, both conditions being characterized by low lipid and lipoprotein plasma levels and enhanced oxidative metabolism . In a procedure for determination of TEARS in edible oils, the sample is placed in a centrifuge at 12000 g before measuring at 532 nm (e = 1.56 x 10 M cm ) . A usual procedure for determination of TEARS in certain complex matrices involves steam distillation of the aldehydes responsible for the value, instead of extraction. In nitrite-cured meats, excess nitrite may cause nitrosation of MDA, thus interfering with distillation. To avoid this interference sulfanilamide is added, which is converted to a diazonium salt and... 

Note that the DP equivalence temperatures in Figure 14 are significantly lower for the atmospheric conditions characteristic of downstream units. Also, as the temperature decreases, the slag dissociation pressure-product decreases much faster than for the plasma, resulting in a super-saturated alkali vapor concentration... 

An older unit of measurement used to express the con-centfation of electrolytes in plasma is the milliequivalent (mEq), which is one thousandth of an equivalent. 

First marketed in the United States in 1996,recombinant factor IX is produced in Chinese hamster ovary cells transfected with the factor IX gene. Blood and plasma products are not used to produce recombinant factor IX nor to stabilize the final product thus recombinant factor IX has an excellent viral safety profile. Clinical trials have shown the product to be safe and efficacious in the treatment of acute bleeding episodes and in the management of bleeding associated with surgical procedures. Although the half-life of recombinant factor IX is similar to that of the plasma-derived products, recovery is approximately 28% lower. As a result, doses of recombinant factor IX concentrate must be higher than those of plasma-derived products to achieve equivalent plasma levels. Because individual pharmacokinetics may vary, recovery and survival studies should be performed to determine optimal treatment. Recombinant factor IX is often considered the treatment of choice for hemophilia B. 

Fibrates have excellent bloavallablllty and are extensively bound to plasma proteins. Because food can significantly enhance their oral absorption, these compounds should be taken either with or just before meals. Fenofibrate was available in Europe and elsewhere as standard tablet and capsule formulations for many years before its approval and marketing in the United States, where it was ihtroduced only after the development of a micronized formulation that allowed better oral absorption, a lower daily dose, and once-daily administration. A 67-mg dose of micronized fenofibrate is bioequivalent to a 100-mg dose of nonmicronized drug. Since that time, two additional tablet formulations have been developed. Abbott Laboratories currently markets TriCor as 48- and 145-mg tablets. The 48-mg formulation is equivalent to previous 54- and 67-mg formulations, and the 145-mg tablet is equivalent to previous 160- and 200-mg formulations. As noted in Table 30.10, fenofibrate is currently available in all of these strengths. 

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