Population dynamics in the Japanese Archipelago since the Pleistocene revealed by the complete mitochondrial genome sequences.

The Japanese Archipelago is widely covered with acidic soil made of volcanic ash, an environment which is detrimental to the preservation of ancient biomolecules. More than 10,000 Palaeolithic and Neolithic sites have been discovered nationwide, but few skeletal remains exist and preservation of DNA is poor. Despite these challenging circumstances, we succeeded in obtaining a complete mitogenome (mitochondrial genome) sequence from Palaeolithic human remains. We also obtained those of Neolithic (the hunting-gathering Jomon and the farming Yayoi cultures) remains, and over 2,000 present-day Japanese. The Palaeolithic mitogenome sequence was not found to be a direct ancestor of any of Jomon, Yayoi, and present-day Japanese people. However, it was an ancestral type of haplogroup M, a basal group of the haplogroup M. Therefore, our results indicate continuity in the maternal gene pool from the Palaeolithic to present-day Japanese. We also found that a vast increase of population size happened and has continued since the Yayoi period, characterized with paddy rice farming. It means that the cultural transition, i.e. rice agriculture, had significant impact on the demographic history of Japanese population.

Discrimination between His-bundle and the right bundle branch during electrophysiologic studies.

BACKGROUND: The purpose of this study was to identify the His-bundle (HB) versus right bundle branch (RBB) during electrophysiologic studies, using the V3 phenomenon, and to compare the timing of HB versus RBB potentials of sinus cycles (His-ventricular [H-V] interval). METHODS: The study enrolled 16 patients without structural heart disease, who underwent electrophysiologic studies during which the H-V interval was within normal limits and the V3 phenomenon was induced during recordings of the HB and the RBB potentials by a multi-electrode catheter. The recording site of the earliest HB potential just before the V3 phenomenon was defined as the branching portion of His bundle (HBBP), the site immediately proximal to the HBBP as the HB, and the site immediately distal to the HBBP as the RBB. RESULTS: The HBBP was identified in all patients. In all cases but one patient, the H-V interval measured at the HB adjacent to the HBBP was > or =35 ms. However, in 12 patients, the H-V interval measured at the RBB adjacent to the HBBP was also > or =35 ms. CONCLUSIONS: The electrophysiologic identification of HB versus RBB by simultaneous recordings of HB and RBB potentials during induction of the V3 phenomenon was feasible. When the discrimination between HB and RBB was based on the measurement of the H-V interval, the proximal portion of the RBB was frequently misidentified as the HB.

Coronary sinus recordings of double potentials associated with retrograde conduction through left atrioventricular accessory pathways.

INTRODUCTION: In some patients with left AV accessory pathway (AP), double potentials are recorded along the coronary sinus (CS) during retrograde AP conduction only. This electrophysiologic study was performed to clarify the origin and clinical significance of double potentials in 11 patients. METHODS AND RESULTS: The direction of activation of the first, relatively blunt component (DP1) was lateral to septal in 5 patients with anterior or anterolateral AP, centrifugal in 2 patients with posterior or posterolateral AP, and septal to lateral in 4 patients with posteroseptal AP, suggesting the earliest activation of DP1 was near the AP. The direction of activation of the second, sharper potentials (DP2) were septal to lateral in all patients. The double potentials were fused in the paraseptal CS region. Pacing from the lateral CS musculature or lateral left atrium reproduced the double potentials. The effective refractory period of the double potentials was reached by ventricular extrastimulation, and the left atrial deflection preceded the double potentials, excluding a ventricular or AP origin. CONCLUSION: In patients with connections between the paraseptal CS musculature and left atrium but no connections more laterally, retrograde left AP conduction is associated with double potentials in the CS recordings. The double potentials represent activation of the left atrial insertion of the AP (DP1) and later activation of the CS musculature (DP2) via connections between the paraseptal CS musculature and left atrium, respectively. The activation pattern of DP1 depends on AP location, thus providing important information for AP localization during CS mapping.

Myocardial bundles with slow conduction properties are present on the left interventricular septal surface of normal human hearts.

INTRODUCTION: The aim of this study was to examine the electrophysiologic characteristics of the normal left interventricular septum (LIVS). METHODS AND RESULTS: We explored the LIVS in search of endocardial potentials following ventricular electrograms during sinus rhythm in 28 patients without structural heart disease. In all patients, low-frequency (mean amplitude: 0.81 +/- 0.33 mV) systolic potentials (LA1) were detected in a basal-to-apical activation sequence (earliest to latest QRS-LA1 interval: 93.3 +/- 10.8 ms to 127.1 +/- 16.6 ms). Programmed stimulation demonstrated decremental conduction properties, and the effective refractory period of the tissue between the ventricular electrogram and LA1 at baseline (376.7 +/- 48.8 ms) was significantly prolonged by disopyramide (421.3 +/- 54.1 ms, P < 0.05 vs baseline). In 21 patients (75%), diastolic potentials (LA2) morphologically similar to LA1 (mean amplitude: 0.52 +/- 0.17 mV) were detected in an apical-to-basal activation sequence (earliest to latest QRS-LA2 interval: 368.9 +/- 32.4 ms to 440.7 +/- 45.8 ms). Para-Hisian pacing with capture of the His bundle showed shorter S-LA1 and S-LA2 intervals compared to the beats without His-bundle capture but with ventricular capture (156.3 +/- 11.2 ms vs 183.2 +/- 12.3 ms, and 385.7 +/- 21.6 ms vs 397.4 +/- 23.4 ms, respectively, P < 0.0001). At the same rate, the LA1-LA2 interval was significantly shorter during right ventricular apical than atrial overdrive pacing (220.4 +/- 23.1 ms vs 261.4 +/- 30.7 ms, P < 0.0001). CONCLUSION: Unique myocardial bundles with slow conduction properties and various electrical connections with the specialized conduction system may exist in the LIVS of normal human hearts.