Effects of simulated solar radiation on type I and type III collagens, collagenase (MMP-1) and stromelysin (MMP-3) gene expression in human dermal fibroblasts cultured in collagen gels.

Understanding the mechanisms responsible for photodamage to the skin is most important for dermatology. 3-D cultures have been used as tools to mimic the in vivo situation for several years. We irradiated such a system containing human dermal fibroblasts cultured in collagen gels, a well-known model considered to be a dermal equivalent, which reproduces the interaction between cells and the surrounding extracellular matrix. The effects of solar irradiation (315-800 nm) on the steady-state levels of the mRNAs of extracellular matrix components (type I and III collagens) and their degrading enzymes (interstitial collagenase, MMP-1 and stromelysin 1, MMP-3) were measured. Exposure to low levels of solar radiation (0-10 J cm-2 in the UVA, i.e. suberythemal UVA doses) caused a transient decrease in type I procollagen mRNA, an increase in MMP-mRNA, and no change in type III procollagen mRNA steady-state levels. These results describe the early changes in the connective tissue of the skin following exposure to low-level solar stimulation, and may help explain the long-term changes in photodamaged skin.

Treatment of malignant primary vasodepressive neurocardiogenic syncope with a rate responsive pacemaker driven by heart contractility.

In a 41-year-old man suffering from frequent syncope, the tilt test reproducibly induced a primary vasodepressive neurocardiogenic syncope. Pharmacotherapy either failed to prevent the syncope induced at the tilt test or was poorly tolerated. In the minutes preceding the syncope, a dramatic increase in heart contractility was sensed by a microaccelerometer located at the tip of a right ventricular pacing electrode. When the tilt test was repeated with the pacemaker programmed in the DDDR mode, high rate dual chamber pacing occurred during the tilt phase and prevented the syncope. Three months after implantation, the patient remains totally symptom free.

Limitations of alginate gels as a culture model for the study of the effects of UVA radiation on human dermal fibroblasts.

Several studies were undertaken to develop three-dimensional (3-D) cell culture models that allow conditions closer to the in vivo situation. To this end, alginate gels were tested as a 3-D cell culture model that might be useful in the study of the effects of UVA on human dermal fibroblasts. Cell culture in alginate gels and the irradiation conditions were optimized. Results showed that optimized cultures in alginate gels experienced considerable cell death on UVA irradiation compared to the classical monolayer cell culture. Viability tests (cell counting and neutral red assay) were performed to show that only UVA-irradiated alginate gels were responsible for this cytotoxicity. The implication of oxygen species in the phototoxicity induced by ultraviolet light has already been described; for this reason we investigated whether oxygen species were involved in the cytotoxicity induced by alginate upon UVA irradiation. It appeared that superoxide anion is not implicated.

Clinical electrophysiologic effects of a single high oral dose of amiodarone.

Several recent reports have described the antiarrhythmic effects of a single high oral dose of amiodarone but clinical electrophysiologic effects have not been reported. The present study was performed to assess electrophysiologic effects in 12 patients. After baseline electrophysiologic studies (EPS) patients were administered a single oral dose of 30 mg/kg of amiodarone. EPS was repeated 7.5 +/- 0.5 hours later. Plasma levels of amiodarone and its metabolite desethylamiodarone were determined at the time of the second EPS, Holter monitoring was performed for 24 hours after amiodarone administration. Amiodarone significantly increased the following parameters: corrected QT interval (+4.5%), functional refractory period of the right atrium (+7%); AH interval (+12.3%), effective refractory period of the atrioventricular node (+18.5%), and cycle length of Wenckebach block (+8.4%). These effects were not correlated with plasma levels of amiodarone and desethylamiodarone. Holter monitoring detected no significant bradycardia or arrhythmia. These findings indicate that the effects of a single high oral dose of amiodarone are the same as those known to be induced by acute intravenous administration.

[Use of esophageal investigation in the mid-term outcome after radiofrequency ablation of intranodal reentrant tachycardia]. / Utilisation de l'exploration oesophagienne pour le suivi à moyen terme après ablation par radiofréquence des tachycardies par réentrée intranodale.

The aim of this prospective study was to assess the medium term results of radio-frequency ablation of intranodal tachycardias by transoesophageal stimulation and recordings. Transoesophageal stimulation was performed on average 9 months after ablation. The anterograde Wenckebach point, the presence of dual nodal conduction and inducibility of nodal tachycardias were determined under basal conditions and after isoproterenol. The follow-up period after ablation was 16.1 +/- 10.2 months. At the time of the oesophageal investigation 25 patients were asymptomatic and 5 had a recurrence of palpitations. The investigation was carried out without complications in all patients and lasted 34.8 +/- 14 minutes. The anterograde Wenckebach point was 340 +/- 78.2 ms and was unchanged compared with the value recorded by endocavitary left atrial stimulation before ablation (332 +/- 63.2 ms). Dual nodal conduction was observed in 19 patients. Nodal tachycardia was inducible in only 2 of the 5 patients with palpitations. Of the asymptomatic patients, 3 had inducible nodal tachycardias after isoproterenol. The authors conclude that oesophageal electrophysiological studies are a simple means of assessing the medium-term results of radiofrequency ablation of intranodal tachycardias. In those patients with a recurrence of symptoms but without documented arrhythmias, failure of radiofrequency ablation may be identified. In addition, the possibility of inducing nodal tachycardias in asymptomatic patients may be detected.

[Bipolar transseptal radiofrequency ablation of posteroseptal bundle of Kent. Apropos of a case]. / Utilisation du mode bipolaire transseptal pour l'ablation par radiofréquence d'un faisceau de Kent postéro-septal. A propos d'un cas.

The posteroseptal localisation of accessory pathways is sometimes responsible for important difficulties for radiofrequency current endocavitary ablation. Some authors have reported the exceptionally rare use of the transseptal bipolar mode for ablation of this type of accessory pathway. The authors report the case of a patient in whom failure of unipolar radiofrequency ablation at the tricuspid and then mitral annulus was followed by immediate success when the bipolar mode was used. The value of recording with the transseptal dipole at the ablation site is emphasised.