Novel Electrocardiographic Criteria for the Diagnosis of Left Ventricular Hypertrophy in the Japanese General Population.

Although there are several diagnostic criteria for left ventricular hypertrophy (LVH), their sensitivity remains low. A recent study reported that the sum of the amplitude of the deepest S wave in any lead (SD) and the S wave in lead V4 (SV4) (SD + SV4) improved sensitivity compared with commonly used criteria. To test whether this new formula improves sensitivity in the Japanese general population, we analyzed 12-lead electrocardiograms for Japanese residents participating in the Iwaki Health Promotion Project (n = 866). Left ventricular mass was calculated by echocardiography, indicating that 156 (18%) of the study population had LVH. In receiver operating characteristic analyses, the sum of the R wave in limb lead Ι (RLΙ) and the S wave in V4 (SV4) (RLΙ + SV4) showed a higher area under the curve (AUC = 0.76) than the Sokolow-Lyon voltage criteria (0.61) and the SD + SV4 criteria (0.63), and almost the same AUC as the Cornell voltage criteria (0.74) and the Cornell product criteria (0.76). The validation study also showed similar results. The cutoff values of RLΙ + SV4 criteria were ≥1.6 mV in men and ≥1.4 mV in women with a sensitivity of 39% and a specificity of 89%, whereas the sensitivity and specificity calculated based on SD + SV4 criteria were 21% and 94%, respectively. Thus, the diagnostic criterion of RLΙ + SV4 seems to be more useful than the previous criteria for diagnosing LVH in the Japanese general population.

Medaka as a model for ECG analysis and the effect of verapamil.

The heart of the medaka, a small fish native to East Asia, has electrophysiological aspects similar to mammalian hearts. We found that the heart rates of medaka were more similar to humans than mice or rats. Medaka exhibited similar electrocardiogram patterns to those of humans, suggesting a similarity in cardiac impulse formation and propagation. Their hearts also exhibited similar responsiveness to verapamil, a calcium channel antagonist; atropine, a parasympathetic nerve blocker; propranolol, a sympathetic ß-adrenergic blocker; and isoproterenol, a sympathetic ß-adrenergic agonist. We successfully analyzed action potentials and cardiac contractile forces in vivo. Verapamil affected action potential duration and reduced heart rate, suggesting the importance of voltage-dependent calcium channels in determining the heart rhythm of medaka. We also analyzed the expression of the voltage-dependent calcium channel ß2 subunit, which participates in channel formation in cardiac myocytes, and found that splice variant type-2 was the only major transcript in the heart. Our results indicate that medaka could be an appropriate animal model for studying cardiovascular pharmacology.

Relationship Between Serum Eicosapentaenoic Acid Levels and J-Waves in a General Population in Japan.

We previously showed that J-waves were found more frequently in patients with low levels of serum eicosapentaenoic acid (EPA) in the acute phase of myocardial infarction, and were associated with the incidence of ischemia-related ventricular arrhythmias. However, the relationship between J-waves and serum EPA levels in a general population remains to be elucidated.The Iwaki Health Promotion Project is an ongoing community-based health promotion study in Iwaki, Hirosaki, which is in northern Japan. A total of 1,052 residents (mean age, 53.9 ± 15.4 years; 390 men) who participated in this project in 2014 were studied. A standard 12-lead electrocardiogram (ECG) was recorded and serum EPA levels were measured to evaluate the relationship between J-waves and serum EPA levels. J-waves were found in 52 (5%) subjects and were observed more frequently in male than female subjects (44 [11%] versus 8 [1%], P < 0.0001). More than half of the J-waves were the notched type (60%), and J-waves were detected most frequently in inferior leads on ECG (52%). The RR interval was longer and QTc duration shorter in subjects with J-waves than those without. No significant difference was found in serum EPA levels between subjects with and without J-waves (70 [49-116] versus 65 [41-106] µg/mL, P = 0.40). In multivariate analysis, male gender and RR interval were independent factors associated with the presence of J-waves.There was no significant relationship between J-waves and serum EPA levels in this general population in Japan. Various mechanisms for manifestation of the J-waves are suggested.

A simple, dual direct expression plasmid system in prokaryotic and mammalian cells.

We introduce a simple, dual direct cloning plasmid system (pgMAX-II) for gene expression analysis in both prokaryotic (Escherichia coli) and mammalian cells. This system, which uses a prokaryotic expression unit adapted from the pgMAX system and a mammalian promoter, is effective for subcloning using the DNA topoisomerase II toxin CcdB. Given that molecular biological cloning systems broadly rely on E. coli for rapid growth, the proposed concept may have wide applicability beyond mammalian cells.

Rapid method for plasmid DNA recombination (Murakami-system).

DNA recombination is a useful technology for cloning and subsequent functional analysis, while standard techniques for plasmid DNA recombination have remained unchanged. In the present study, we introduced rapid method for plasmid DNA recombination, which we named "Murakami-system", to complete the experiments in under 33 h. For this purpose, we selected the following: PCR amplification with 25 cycles and E. coli strain with rapid growth (incubation time of 6-8 h). In addition, we selected rapid plasmid DNA purification (mini-prep; ∼10 min) and rapid restriction enzyme incubation (20 min). This recombination system enabled rapid plasmid DNA recombination within 24-33 h, which could be useful in various fields. We also established a 1-day method for competent cell preparation. Our rapid recombination system allowed several sessions of plasmid DNA recombination to be performed every week, which improves the functional analysis of various genes.•"Rapid method for plasmid DNA recombination (Murakami-system).•E. coli strain with rapid growth (incubation time of 6-8 h).•Combination of rapid protocols (PCR, electrophoresis, DNA purification, ligation, and mini-prep) enabled plasmid DNA recombination within 24-33 h.

Enhanced ß-adrenergic response in mice with dominant-negative expression of the PKD2L1 channel.

Polycystic kidney disease (PKD) is the most common genetic cause of kidney failure in humans. Among the various PKD-related molecules, PKD2L1 forms cation channels, but its physiological importance is obscure. In the present study, we established a transgenic mouse line by overexpressing the dominant-negative form of the mouse PKD2L1 gene (i.e., lacking the pore-forming domain). The resulting PKD2L1del-Tg mice exhibited supraventricular premature contraction, as well as enhanced sensitivity to ß-adrenergic stimulation and unstable R-R intervals in electrocardiography. During spontaneous atrial contraction, PKD2L1del-Tg atria showed enhanced sensitivity to isoproterenol, norepinephrine, and epinephrine. Action potential recording revealed a shortened action potential duration in PKD2L1del-Tg atria in response to isoproterenol. These findings indicated increased adrenergic sensitivity in PKD2L1del-Tg mice, suggesting that PKD2L1 is involved in sympathetic regulation.

Decreased cardiac pacemaking and attenuated ß-adrenergic response in TRIC-A knockout mice.

Changes in intracellular calcium levels in the sinus node modulate cardiac pacemaking (the calcium clock). Trimeric intracellular cation (TRIC) channels are counterion channels on the surface of the sarcoplasmic reticulum and compensate for calcium release from ryanodine receptors, which play a major role in calcium-induced calcium release (CICR) and the calcium clock. TRIC channels are expected to affect the calcium clock in the sinus node. However, their physiological importance in cardiac rhythm formation remains unclear. We evaluated the importance of TRIC channels on cardiac pacemaking using TRIC-A-null (TRIC-A-/-) as well as TRIC-B+/-mice. Although systolic blood pressure (SBP) was not significantly different between wild-type (WT), TRIC-B+/-, and TRIC-A-/-mice, heart rate (HR) was significantly lower in TRIC-A-/-mice than other lines. Interestingly, HR and SBP showed a positive correlation in WT and TRIC-B+/-mice, while no such correlation was observed in TRIC-A-/-mice, suggesting modification of the blood pressure regulatory system in these mice. Isoproterenol (0.3 mg/kg) increased the HR in WT mice (98.8 ±â€…15.1 bpm), whereas a decreased response in HR was observed in TRIC-A-/-mice (23.8 ±â€…5.8 bpm), suggesting decreased sympathetic responses in TRIC-A-/-mice. Electrocardiography revealed unstable R-R intervals in TRIC-A-/-mice. Furthermore, TRIC-A-/-mice sometimes showed sinus pauses, suggesting a significant role of TRIC-A channels in cardiac pacemaking. In isolated atrium contraction or action potential recording, TRIC-A-/-mice showed decreased response to a ß-adrenergic sympathetic nerve agonist (isoproterenol, 100 nM), indicating decreased sympathetic responses. In summary, TRIC-A-/-mice showed decreased cardiac pacemaking in the sinus node and attenuated responses to ß-adrenergic stimulation, indicating the involvement of TRIC-A channels in cardiac rhythm formation and decreased sympathetic responses.

Whole genome association study of rheumatoid arthritis using 27 039 microsatellites.

A major goal of current human genome-wide studies is to identify the genetic basis of complex disorders. However, the availability of an unbiased, reliable, cost efficient and comprehensive methodology to analyze the entire genome for complex disease association is still largely lacking or problematic. Therefore, we have developed a practical and efficient strategy for whole genome association studies of complex diseases by charting the human genome at 100 kb intervals using a collection of 27,039 microsatellites and the DNA pooling method in three successive genomic screens of independent case-control populations. The final step in our methodology consists of fine mapping of the candidate susceptible DNA regions by single nucleotide polymorphisms (SNPs) analysis. This approach was validated upon application to rheumatoid arthritis, a destructive joint disease affecting up to 1% of the population. A total of 47 candidate regions were identified. The top seven loci, withstanding the most stringent statistical tests, were dissected down to individual genes and/or SNPs on four chromosomes, including the previously known 6p21.3-encoded Major Histocompatibility Complex gene, HLA-DRB1. Hence, microsatellite-based genome-wide association analysis complemented by end stage SNP typing provides a new tool for genetic dissection of multifactorial pathologies including common diseases.