Determination of cortisol in human blood sera by a new Ag(III) complex-luminol chemiluminescent system.

A new chemiluminescence (CL) system based on the reaction of Ag(III) complex with luminol is, for the first time, reported in this work. Incorporated with a flow injection analyses (FIA), the new CL system has been applied for the determination of free cortisol in human sera. The system is based on the CL reaction of luminol with Ag(III) in alkaline solutions, while cortisol can dramatically enhance CL intensities. Under optimum conditions, CL intensities are proportional to concentration of cortisol in the range of 0.05-7.5 nM. The limit of detection is 2.0x10(-11) M (3sigma), with a relative standard deviation (n=11) of 1.9% for 3.5x10(-9) M cortisol. Eight human blood serum samples were all handled by solid-phase extraction (SPE) clean-up and enrichment before detection. This detection system is highly sensitive and convenient and may find wide applications. Based on the chemiluminescent spectra, a possible reaction mechanism is also suggested.

[Screening of stage-specific expression genes of Spirometra erinacei-europaei plerocercoid by mRNA differential display technique].

OBJECTIVE: To screen stage-specific expression genes of plerocercoid of Spirometra erinacei-europaei. METHODS: RNA was extracted by the acid guanidinium thiocyanate-phenol-chloroform from plerocercoid and adult worm of Spirometra erinacei-europaei. Contaminated DNA in the RNA was digested by RNase-free DNase. cDNA was synthesized by using T12MA, T12MC, T12MG and T12MT primers, and PCR was then done using the same T12MN and one random primers. The PCR products were fractionated on 8% denatured polyacrylamide gel, differential bands of plerocercoid found in the gel were cut out, amplified by PCR and sequenced after the gel was dried out and autoradiographed. Northern hybridization was conducted to identify the stage-specific expression genes. RESULTS: Eleven differential bands were selected from the gel and classified into 3 kinds of gene fragments by hybridization after they were amplified by PCR. The fragments 1 and 2 were confirmed to express specifically in plerocercoid by Northern hybridization, but the fragment 3 was expressed in both plerocercoid and adult worm. When the 3 gene fragments were homologically analyzed in GenBank, the sequence which was homologous with the fragments 1 and 2 was not found, but the fragment 3 had high homology with many kinds of 28S rRNA. CONCLUSION: The gene expression of plerocercoid was different from that of adult worm probably because they live in different hosts. Two kinds of different gene fragments in plerocercoid were identified by mRNA differential display technique.