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Purpose: Although it is deemed important, right atrial ablation is not considered feasible with bipolar radiofrequency alone. Normally, unipolar devices are used to complete the tricuspid connecting lines. We describe a simple technique to achieve a complete maze-like set of right ablations using a standard bipolar radiofrequency device., Description: Thirty-four patients underwent concomitant ablation with a right set of lines performed using bipolar radiofrequency only. The epicardium adjacent to the right atriotomy was entered and after separating the sulcus fat from the atrial wall, the deepest portion of the atrioventricular groove was developed bluntly with the scissors down to the tricuspid annulus. The tricuspid connecting lines were then performed with bipolar radiofrequency in an endo-epicardial fashion., Evaluation: No ablation-related complications occurred. No patient died. Three patients required pacemaker implantation. At a mean follow-up of 8 +/- 5, 85% of the patients were free from arrhythmias. At 6 months 20 of 24 patients (83%) were in stable sinus rhythm., Conclusions: All the maze III right atrial ablations can be performed using a bipolar radiofrequency device alone. The procedure is safe and easily reproducible on a regular basis.

Sister-chromatid exchanges (SCE) were analyzed in mouse spermatogonia using two different protocols for bromodeoxyuridine (BrdU) exposure and detection. With the classical approach, based on subcutaneous implantation of agar-coated BrdU tablets and fluorescence plus Giemsa (FPG) staining a satisfactory differentiation of spermatogonial metaphases was obtained with 50 or 25 mg BrdU per mouse (two or one tablets respectively). Alternatively, the immunodetection of BrdU was carried out after exposure to a very low BrdU concentration (three injections i.p., 3 mg/kg b.w. each, at 5-h intervals), and after exposure to one BrdU tablet; SCE frequencies evaluated in this way were lower than those found after classical FPG staining, even when the mice were exposed to the same BrdU concentration (one tablet, 25 mg BrdU). We concluded that the two methodologies may have different sensitivities with respect to SCE detection. In addition, when the effect of a treatment with mitomycin C was tested (1 mg/kg b.w., at time intervals ranging from 24 h to 5 days), no sister-chromatid differentiation was obtained with the multiple injection protocol, or with one BrdU tablet. By contrast, with two BrdU tablets and FPG, well differentiated metaphases were found at any time interval tested after MMC treatment, and the peak frequency of SCE (3.4 times the baseline) was observed at 55 h after treatment, as expected on the basis of cell cycle duration in spermatogonia. In summary, even though the use of medium-low concentrations of BrdU was successful in untreated animals, these protocols appeared inadequate to detect SCE induction by MMC. It is possible that, in the presence of cell cycle delay induced by the treatment, interferences with the rate of BrdU uptake produce an unsatisfactory differentiation of sister chromatids.

The frequency of sister-chromatid exchanges (SCE) was evaluated in mouse bone marrow cells at different time intervals (from 19 h to 10 days) after treatment i.p. with mitomycin C (MMC; 1 and 2 mg/kg body weight). Significantly higher frequencies of SCE were found during the first week after treatment, at both doses tested. This result confirms that chromosomal lesions induced by MMC in the mouse may persist in bone marrow cells, in agreement with previous evidence based on chromosomal aberration analysis in the same cell population. In addition, the observation of a unimodal distribution of SCE/cell frequencies at each time tested indicates that the bone marrow cell population on the whole is affected by increased SCE frequency, i.e., that persistent chromosomal lesions may be transmitted along with cell proliferation.