A study of bismuth-film electrodes for the detection of trace metals by anodic stripping voltammetry and their application to the determination of Pb and Zn in tapwater and human hair.

This work reports the simultaneous determination of Cd(II), Pb(II) and Zn(II) at the low mug l(-1) concentration levels by square wave anodic stripping voltammetry (SWASV) on a bismuth-film electrode (BFE) plated in situ. The metal ions and bismuth were simultaneously deposited by reduction at -1.4 V on a rotating glassy carbon disk electrode. Then, the preconcentrated metals were oxidised by scanning the potential of the electrode from -1.4 to 0 V using a square-wave waveform. The stripping current arising from the oxidation of each metal was related to the concentration of each metal in the sample. The parameters for the simultaneous determination of the three metals were investigated with the view to apply this type of voltammetric sensor to real samples containing low concentrations of metals. Using the selected conditions, the limits of detection were 0.2 mug l(-1) for Cd and for Pb and 0.7 mug l(-1) for Zn at a preconcentration time of 10 min. Finally, BFE's were successfully applied to the determination of Pb and Zn in tapwater and human hair and the results were in satisfactory statistical agreement with atomic absorption spectroscopy (AAS).

Prognostic significance of the sequential detection of circulating melanoma cells by RT-PCR in high-risk melanoma patients receiving adjuvant interferon.

The purpose of this study was to address the prognostic significance of circulating melanoma cells by reverse transcriptase-polymerase chain reaction in the peripheral blood of stage IIB and III melanoma patients on high-dose adjuvant interferon at multiple sequential time points from initiation of treatment. Tyrosinase mRNA in peripheral blood from these patients was assayed by reverse transcriptase polymerase chain reaction prior to initiation of adjuvant interferon, at completion of 1 month of intravenous interferon and at 3 monthly intervals until progression. Four hundred and eighteen blood samples from 60 melanoma patients were analysed. The median follow-up time calculated from the time of inclusion in the study was 23 months (range 2-38 months). Tyrosinase mRNA in blood was detected in 42 (70%) of 60 patients: 16 (76%) of 21 stage IIB patients and 26 (66% ) of 39 stage III patients. The presence of tyrosinase mRNA in blood was correlated with a shorter disease-free survival (P : 0.03) and in multivariante analysis was an independent prognostic factor for relapse. Patients who seroconverted to a negative reverse-transcriptase-polymerase chain reaction after induction treatment had a significantly lower probability of recurrence. The presence of circulating melanoma cells is a marker of a high relapse risk and shorter disease-free survival whether detected postoperatively or during follow-up. Tyrosinase mRNA amplification by reverse-transcriptase-polymerase chain reaction may be a useful tool for monitoring the efficacy of adjuvant treatment in stage IIB and III melanoma patients.

RT-PCR for tyrosinase expression as a molecular marker in malignant melanoma.

As the incidence of malignant melanoma steadily increases the need for markers in detection of early metastasis and guidance of therapy has become urgent. Presence of melanoma cells in patient peripheral blood, lymph nodes or bone marrow (BM) specimens could indicate tumour dissemination, and thus a high risk of metastasis. In 1991 coupled Reverse Transcription and Polymerase Chain Reaction (RT-PCR) was firstly used to detect tyrosinase mRNA in the peripheral blood of melanoma patients. Since then numerous studies have evaluated the significance of tyrosinase expression in bone marrow specimens, lymph nodes and blood from melanoma patients and there results indicate that this method might have important clinical applications in melanoma management.