Negative receptor assays

To further evaluate whether the addition of nuclear ERP has any predictive value, 95 patients were analyzed (L5) for cytosolic ERP and PRP and nuclear ERP. The incidence of cytosolic ERP+ was 74%, cytosolic PRP+ was 70%, and nuclear ERP+ was 52%. There was a trend to higher incidence of cytosolic ERP+ with increasing age, from 45% in patients less than 45 years old to 85% in patients over 70 years of age. The incidence of nuclear ERP+ was especially low among premenopausal patients, but it did not show constant correlation with age in postmenopausal women. There was 40% concordance of positivity, 14% concordance of negativity, and 46% nonconcordance in the three receptor assays, with a wide variety of other combinations. 

Until recently, most assays used to demonstrate receptor oligomerization were based on biochemical approaches such as immunoprecipitation or crosslinking. Alternatively, dominant negative receptor mutants were employed to abrogate wild-type receptor functions by forming nonfunctional complexes (26). New approaches based on energy transfer between fluorochromes... 

In order to avoid the selection and amplification of RNA molecules that do not bind to the target site, two assays for in vitro selection are both employed after SELEX cycle 3. In addition a negative preselection step can be used at which unspecific binders to nitrocellulose (used for separation of receptor-bound from unbound RNA molecules) are discarded (see Subheading 3.7). 

Endotoxicity results from the interaction of a bacterial cell envelope component (e.g., LPS or PG with a cell surface receptor constituting part of the nonspecific immune system, (i.e., a toll-like receptor on white blood cells). This results in the production of cytokines [e.g., interleukin 1 (IL-1) or tumor necrosis factor (TNF)] as part of an intracellular enzyme cascade which can cause severe tissue injury. Bioassays or immunoassays can be used to detect such reactions respectively. As noted above the most widely used bioassay is the LAL assay. A lysate of amoebo-cytes of the horseshoe crab (Limulus) contains an enzymatic clotting cascade which is activated by extremely low levels of LPS (nanogram levels or lower). There are variants of this assay that can detect PG, but they are not as widely used. As noted above, other bioassays employ cultured cell lines that respond to LPS or PG, respectively. Unfortunately bioassays are highly amenable to false positives (from the presence of cross-reactive substances) or false negatives from inhibition (by contaminants present in the sample) [10]. A detailed discussion of these assays is beyond the scope of this chapter and has been reviewed elsewhere [1]. 

Fibroblasts were classified as normal FH heterozygous or receptor negative FH homozygous following characterization according to the four biochemical assays described by Goldstein... 

Most steroid-sensitive cancers express specific cell surface receptors. Prednisone-sensitive lymphomas, estrogen-sensitive breast cancers, and prostatic cancers express specific receptors for corticosteroids, estrogens, and androgens, respectively. It is now possible to assay tumor specimens for steroid receptor content and to identify which individual patients are likely to benefit from hormonal therapy. Measurement of the estrogen receptor (ER) and progesterone receptor (PR) proteins in breast cancer tissue is now standard clinical practice. ER or PR positivity predicts response to hormonal therapy, whereas patients whose tumors are ER-negative generally fail to respond to such treatment. 

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