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At least 55 records · Page 3Linked to original sources
PubMed2006

Behavior of atrial ectopic beats before and after pulmonary vein isolation in patients with atrial fibrillation: a reduction in the number and arrhythmogenicity of ectopic firings.

BACKGROUND: No studies evaluating in a quantitative manner the effect of pulmonary vein (PV) isolation on the behavior of atrial premature beats have been reported. OBJECTIVES: The purpose of this study was to reveal the behavior of atrial premature beats before and after PV isolation in patients with paroxysmal atrial fibrillation (AF). METHODS: In 108 patients free from AF following PV isolation, both the number of atrial premature beats and their coupling intervals before and following PV isolation were evaluated with periodic 24-hour ambulatory monitoring. RESULTS: After a successful PV isolation procedure (group 1, n = 78), the number of atrial premature beats significantly decreased with two distinct time courses: an acute reduction on the following day and a subsequent gradual decrease throughout the whole observation period. The mean atrial premature beat coupling interval at baseline was 420 +/- 30 ms, which was significantly prolonged to 560 +/- 100 ms at 3 months after PV isolation (P <.01). Although patients with AF recurrence after PV isolation (group 2, n = 30) had transiently depressed atrial premature beats shortly after the procedure, they recovered to the former level 3 months after PV isolation. Repeat PV isolation targeting the reconnected PVs successfully suppressed these residual atrial premature beats both in their number and the coupling interval in a manner similar to those in group 1. CONCLUSION: Successful PV isolation reduced the number of atrial premature beats with both rapid and gradual time courses. The residual atrial premature beats appeared less arrhythmogenic, with longer coupling intervals than those at baseline. AF recurrences after PV isolation were associated with increased atrial premature beat number and shortened coupling interval, which were depressed by reisolation of reconnected PVs.

Atrial Fibrillation↗
PubMedDate not supplied

Synthesis of fast myosin induced by fast ectopic innervation of rat soleus muscle is restricted to the ectopic endplate region.

Skeletal muscle fibres, long multinucleated cells, arise by fusion of mononucleated myoblasts to form a myotube that matures into the adult fibre. The two major types of mature fibre, fast and slow fibres, differ physiologically in their rate of isotonic shortening. At the molecular level these type-specific physiological properties are ascribed to different isoforms of myosin, a major protein involved in shortening. Differentiation of fast and slow fibres seems to be under the control of motoneurones, and mature fibres are innervated by only one motoneurone. When rat soleus muscle (SOL, a slow muscle) is dually innervated with a fast nerve, it acquires some properties of a fast muscle, that is, low sensitivity to caffeine and high glycogen content. We report here that in dually innervated soleus muscle the foreign fast nerve induces synthesis of fast isoforms of myosin, but only in the segment of the muscle fibre that is close to the foreign endplate. The localized influence of the nerve endplates suggest that factors controlling the phenotypic expression of the muscle fibre have a short range of activity.

Animals↗
PubMed2000

Ectopic expression of c-myc fails to overcome downregulation of telomerase activity induced by herbimycin A, but ectopic hTERT expression overcomes it.

Telomerase plays a key role in the maintenance of chromosomal stability in tumors, but the mechanism regulating telomerase activity is still unclear. Recent studies have suggested that c-myc may be vital for regulation of hTERT mRNA expression and telomerase activity. In this study, we investigated the changes of telomerase activity and telomerase-related genes induced by herbimycin A in K562 human chronic myelogeous leukemic cells. Telomerase activity showed a biphasic pattern in herbimycin A-treated K562 cells. Initially, the telomerase activity decreased along with the decline of cells in S and G2/M phases, but it recovered slightly at the end of treatment. Expression of mRNA for the telomerase catalytic subunit (hTERT) was decreased before the decline of telomerase activity, and increased slightly before the reactivation of telomerase activity. During herbimycin A treatment, both c-myc and cyclin D1 mRNA showed transient downregulation before the increase of G1 cells. Herbimycin A treatment caused the downregulation of both telomerase activity and hTERT mRNA in cyclin D1-transfected K562 cells, while telomerase activity was partially restored in c-Myc-transfected cells. In contrast, hTERT-transfected K562 cells maintained a high level of telomerase activity during herbimycin A treatment. Neither the template RNA component of telomerase (hTERC) nor telomerase-associated protein (TEP-1) were altered in any of the transfected K562 cells. These results indicate that telomerase activity is mainly regulated by hTERT, and that c-Myc protein is one of the positive regulators of hTERT in leukemic cells but is not enough to counteract the downregulation of telomerase activity by herbimycin A completely.

Benzoquinones↗