Bias in estimations of DNA content by competitive polymerase chain reaction.

Competitive PCR is a highly sensitive method for specific DNA quantification. Despite the lack of studies related to the accuracy of the method it has been widely used. Here we present a simulation model for competitive PCR, which takes into account the efficiency decay as a linear relationship of the total product yield. The model helped us to study the kind and magnitude of errors that arise from quantitative and semiquantitative competitive PCR protocols and to find ways to minimize them. The simulation data suggest that differences in amplification efficiency between target and standard templates induce stronger biases in quantitative than in semiquantitative competitive PCR. Quantitative competitive PCR can only be used when both efficiencies are equal. In contrast, semiquantitative competitive PCR can be used even when the target is amplified with a higher efficiency than the standard, since under such conditions the method tends to underestimate the differences in initial DNA content. These predictions have been confirmed with experimental data and show that the estimation of the amplification efficiencies is a prerequisite for the use of quantitative and semiquantitative competitive PCR. A simple method for this estimation is also presented.

Inhibition of tumor necrosis factor-alpha action within the CNS markedly reduces the plasma adrenocorticotropin response to peripheral local inflammation in rats.

The present study tested the hypothesis that the cytokine tumor necrosis factor-alpha (TNF-alpha) is an important CNS mediator of the hypothalamo-pituitary-adrenal (HPA) axis response to local inflammation in the rat. Recombinant murine TNF-alpha administered directly into the cerebroventricles of normal rats produced a dose-dependent increase in plasma adrenocorticotropin (ACTH) concentration. Local inflammation induced by the intramuscular injection of turpentine (50 microl/100 gm body weight) also produced an increase in plasma ACTH, peaking at 160-200 pg/ml at 7.5 hr after injection (compared with 10-30 pg/ml in controls). Intracerebroventricular pretreatment with either 5 microl of anti-TNF-alpha antiserum or 1-50 microg of soluble TNF receptor construct (rhTNFR:Fc) reduced the peak of the ACTH response to local inflammation by 62-72%. In contrast, intravenous treatment with the same doses of anti-TNF-alpha or rhTNFR:Fc had no significant effect on the ACTH response to local inflammation. Although these data indicated an action of TNF-alpha specifically within the brain, no increase in brain TNF-alpha protein (measured by bioassay) or mRNA (assessed using either in situ hybridization histochemical or semi-quantitative RT-PCR procedures) was demonstrable during the onset or peak of HPA activation produced by local inflammation. Furthermore, increased passage of TNF-alpha from blood to brain seems unlikely, because inflammation did not affect plasma TNF-alpha biological activity. Collectively these data demonstrate that TNF-alpha action within the brain is critical to the elaboration of the HPA axis response to local inflammation in the rat, but they indicate that increases in cerebral TNF-alpha synthesis are not a necessary accompaniment.

Molecular cloning and identification of a serine/threonine protein kinase of the second-messenger subfamily.

A partial cDNA was isolated that encoded a protein kinase, termed rac (related to the A and C kinases). This cDNA was subsequently used to screen libraries derived from the human cell lines MCF-7 and WI38 and led to the isolation of full-length cDNA clones. DNA sequence analysis identified an open reading frame of 1440 base pairs encoding a protein of 480 amino acids (Mr, 55,716). This result was supported by the synthesis of a Mr 58,000 protein in an in vitro translation system that used RNA transcribed from cloned cDNAs with SP6 RNA polymerase. The predicted protein contains consensus sequences characteristic of a protein kinase catalytic domain and shows 73% and 68% similarity to protein kinase C and the cAMP-dependent protein kinase, respectively. Northern (RNA) analysis revealed a single mRNA transcript of 3.2 kilobases that varied up to 300-fold between different cell lines. Specific antisera directed towards the carboxyl terminal of the rac protein kinase were prepared and used to identify that phosphorylated several substrates in immunoprecipitates prepared with the rac-specific antisera.