Assays, definition

Fig. 2. 12-plexed MassEXTEND reaction results. To exemplify the concept, the assay definitions for one of the 12 assays (primer, potential pausing signals, and predicted alleles) are indicated with dotted lines. In the depicted case, the individual is homozygous A. The MassEXTEND primer is fully extended. Each mass signal provides a unique identifier for the presence of an allele in a specific assay. 

It was agreed at the workshop that endocrine disrupting activity could only be adequately defined in terms of effects in intact animals, be they juvenile or adult, or in the offspring of exposed parents. For many chemicals, evidence of endocrine disrupting activity has been obtained only by the use of in vitro models, such as hormone binding assays. It was accepted, therefore, that chemicals active in such models should be considered only as potential EDs and should be distinguished from those established as active in vivo. For such chemicals, an alternative definition was recommended ... 

In many situations, the actual molar amount of the enzyme is not known. However, its amount can be expressed in terms of the activity observed. The International Commission on Enzymes defines One International Unit of enzyme as the amount that catalyzes the formation of one micromole of product in one minute. (Because enzymes are very sensitive to factors such as pH, temperature, and ionic strength, the conditions of assay must be specified.) Another definition for units of enzyme activity is the katal. One katal is that amount of enzyme catalyzing the conversion of one mole of substrate to product in one second. Thus, one katal equals 6X10 international units. 

Rational design, 148-149, 152 Real-time assays, 83, 88 Receptor(s). See also Drug receptors affinity for, 6, 63 allosteric model of, 143 Clark s work, 3 classical model of, 44-45 concept of, 2-4 conformations, 13-14, 13 Of conservation equation for, 76 constitutive activity of, 49-51 coupling of, 27 definition of, 2 desensitization of, 34 efficacy for, 6... 

Receptor assays, 251 Receptor compartment definition of, 35 drug removal from, 36f free drug concentration in, 39 Receptor density... 

A biomarker is here defined as a biological response to an environmental chemical at the individual level or below, which demonstrates a departure from normality. Responses at higher levels of biological organization are not, according to this definition, termed biomarkers. Where such biological responses can be readily measnred, they may provide the basis for biomarker assays, which can be nsed to stndy the effects of chemicals in the laboratory or, most importantly, in the field. There is also interest in their employment as tools for the environmental risk assessment of chemicals. 

Definitive diagnosis made by assay of appropriate enzyme, often using leukocytes... 

Assessment and definition of sensitivity are often described for quantitative analysis but are of equal importance for qualitative devices of the dip-stick type that are very popular for farm- or field-based screening assays. Because of the somewhat subjective nature of visually assessed assays, the assay s sensitivity must be validated using a number of observers to determine at what level a test is deemed positive. The number of false positives and false negatives must be carefully determined in order to balance consumer safety and potential economic loss to animal producers. 

Experiments with aldicarb sulfone in ground beef involved simple extraction with acetonitrile during tissue homogenization and resulted in a definite immunoassay response at the tolerance level of 10 qg kg A moderate, but rather consistent, matrix effect was observed. A more severe matrix effect was observed in bovine milk, blood, and urine. For the liquid matrices, sample dilution was not a satisfactory strategy, because the assay variability increased at lower concentrations, negating any benefit of reducing the matrix effect. This work clearly demonsttated that matrix effects are... 

Laboratory confirmation is vital to effective treatment of HSV, especially in individuals in whom a clinical diagnosis cannot be obtained. There are several methods by which a definitive diagnosis may be acquired, and these include virologic typing, serologic diagnosis, rapid point-of-care antigen detection, enzyme-linked immunosorbent assay (ELISA), immunoblot, and DNA polymerase chain reaction.27... 

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