Identification of dinucleoside polyphosphates by matrix-assisted laser desorption/ionisation post-source decay mass spectrometry.

Dinucleoside polyphosphates are a group of intra- and extracellular mediators controlling numerous physiological functions. In this study dinucleoside polyphosphates were examined by positive ion matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MADLI-TOFMS). 3-Hydroxypicolinic acid was used as UV-absorbing matrix. For the individual dinucleoside polyphosphates Ap(n)A (n = 2-7), Ap(n)G (n = 2-6) and Gp(n)G (n = 2-6), MALDI post-source decay (PSD) mass spectra were measured. Each mass peak in the MALDI-PSD mass spectra could be assigned to individual fragments of dinucleoside polyphosphates. The comparison of the fragmentation patterns of the dinucleoside polyphosphates presented here demonstrates that dinucleoside polyphosphates preferably cleave to fragment ions consisting of the corresponding mononucleoside polyphosphates as well as the corresponding nucleosides and bases during flight in the field-free drift path of the MALDI mass spectrometer. Therefore, the MALDI-PSD approach described here is suitable for identification of other dinucleoside polyphosphates. The present MALDI-PSD mass spectra may be used as MALDI-PSD mass reference spectra for future identification of dinucleoside polyphosphates and other nucleotides.

[Clinical value of native and contrast enhanced MRI in staging prostatic carcinoma before planned radical prostatectomy]. / Klinischer Stellenwert der nativen und KM-unterstützten MRT im Staging des Prostatakarzinoms vor geplanter radikaler Prostatektomie.

PURPOSE: To assess the clinical value of MRI with and without contrast agent in the staging of prostatic carcinoma. Relevance for surgical management. METHODS: 60 patients with carcinoma proven by biopsy or suspected prostatic carcinoma were evaluated with MRI. The examinations were performed in a 1.5 T (Philips ACS-NT Gyroscan) imager with multiplanar orientations before and after intravenous application of 0.1 mmol/kg/bw Gadodiamide (Omniscan-Nycomed/Amersham). The gold standard was histology after radical prostatectomy and in case of non-operability the consensual final staging. RESULTS: Compared to histology MRI revealed a sensitivity of 75% and a specificity of 82% in the differentiation of locally advanced carcinoma (T 3/4). Including the non-surgical cases MRI showed a sensitivity of 82.5% and a specificity of 86%. Interindividual analysis showed no difference in diagnostic accuracy between the non-enhanced and the contrast-enhanced techniques. In 23% of cases (n = 14) MRI induced changes in patient management. CONCLUSIONS: MRI is an accurate procedure in the local staging of prostatic carcinoma. In combination with clinical findings, PSA, and grading scores MRI has a significant influence on treatment selection. Contrast agent administration does not seem to increase the diagnostic accuracy significantly.

[Localized 31P-NMR-spectroscopy using ISIS (image-selected in vivo spectroscopy) and surface coils: methodology and initial applications to studies of the liver, the transplanted kidney and the mediastinum]. / Lokalisierte 31P-NMR-Spektroskopie mit ISIS und Oberflächenspule: Methodik und erste Anwendungen bei der Untersuchung von Leber, Transplantatniere und Mediastinum.

A new method for image-guided localized phosphorus NMR spectroscopy of superficial tissues has been investigated using a 1.5 Tesla whole-body-MR-System. We used a surface coil combined with adiabatic excitation pulses and a modified ISIS sequence. This approach is related to imaging sequences and thus permits a flexible and accurate determination of the volume of interest from "conventional" proton images. The scope and advantages of the method are demonstrated by phantom studies. Clinical applications to the liver, renal transplants, and the mediastinum are described.