Myocardial repolarization time, J-point to T-peak and T-peak to T-end intervals, have different heart rate dependency and autonomic nerve interference in healthy prepubertal children.

OBJECTIVE: The JT interval of the myocardial repolarization time can be divided into Jpoint to T-peak interval (JTp) and T-peak to T-end interval (Tpe). It is well known that the JT interval is dependent on the heart rate, but little is known regarding heart rate dependence for JTp and Tpe. The aim of the present study was to clarify the heart rate dependence of JTp and Tpe and to elucidate the interference of autonomic nervous activity with these parameters. METHODS: We evaluated 50 prepubertal children (mean age: 6.4 ± 0.5 years; male:female, 22:28) without heart disease. JTp, Tpe, and the preceding RR intervals were measured using 120 consecutive beats (lead CM5). First, the relationships between the RR interval and JTp and Tpe were evaluated by Pearson's correlation coefficient. Second, to evaluate autonomic interference with JTp and Tpe, the degree of coherence between RR interval variability and JTp or Tpe variability was calculated using spectral analysis. RESULTS: Significant positive correlations were observed between the RR interval and JTp (y = 0.116x + 105.5; r = 0.594, p < 0.001) and between the RR interval and Tpe (y = 0.037x + 44.7; r = 0.432, p < 0.001). Tpe variability had a lower degree of coherence with RR interval variability (range: 0.039-0.5 Hz) than with JTp variability (0.401 [interquartile range, 0.352-0.460] vs. 0.593 [0.503-0.664], respectively; p < 0.001). CONCLUSIONS: Tpe had lower heart rate dependence and a lower degree of autonomic nervous interference than did JTp.

QT Variability Index is Correlated with Autonomic Nerve Activity in Healthy Children.

The QT variability index (QTVI), which measures the instability of myocardial repolarization, is usually calculated from a single electrocardiogram (ECG) recording and can be easily applied in children. It is well known that frequency analysis of heart rate variability (HRV) can detect autonomic balance, but it is not clear whether QTVI is correlated with autonomic tone. Therefore, we evaluated the association between QTVI and HRV to elucidate whether QTVI is correlated with autonomic nerve activity. Apparently, healthy 320 children aged 0-7 years who visited Fujita Health University Hospital for heart checkup examinations were included. The RR and QT intervals of 60 continuous heart beats were measured, and the QTVI was calculated using the formula of Berger et al. Frequency analysis of HRV, including the QTVI analysis region, was conducted for 2 min and the ratio of low-frequency (LF) components to high-frequency (HF) components (LF/HF) and HF/(LF + HF) ratio was calculated as indicators of autonomic nerve activity. Then, the correlations between QTVI and these parameters were assessed. QTVI showed a significant positive correlation with LF/HF ratio (r = 0.45, p < 0.001) and negative correlation with HF/(LF + HF) ratio (r = -0.429, p < 0.001). These correlations remained after adjustment for sex and age. QTVI, which is calculated from non-invasive ECG and can detect abnormal myocardial repolarization, is significantly correlated with frequency analysis of HRV parameters. QTVI reflects autonomic nerve balance in children.

Efficient Surface Passivation of Ti-Based Layered Materials by a Nonfluorine Branched Copolymer for Durable and High-Power Sodium-Ion Batteries.

There is a crucial need for low-cost energy storage technology based on abundant sodium ions to realize sustainable development with renewable energy resources. Poly(vinylidene fluoride) (PVDF) is applied as a binder in sodium-ion batteries (SIBs). Nevertheless, PVDF is also known to suffer from a larger irreversible capacity, especially when PVDF is used as the binder of negative electrode materials. In this research, a poly(acrylonitrile)-grafted poly(vinyl alcohol) copolymer (PVA-g-PAN) is tested as a binder with Ti-based layered oxides as potential negative electrode materials for SIBs. The chemical stability tests of PVDF and PVA-g-PAN contacted with metallic sodium have been conducted, which reveals that PVDF experiences a defluorination process, while PVA-g-PAN demonstrates excellent chemical stability. Composite electrodes with PVA-g-PAN demonstrate superior electrochemical performances when compared with the PVDF binder, allowing improvement for initial CE, higher rate capability, and long cyclability over 1500 cycles. Detailed characterization of electrodes via soft X-ray photoelectron spectroscopy and field emission scanning electron microscopy demonstrates that the PVA-g-PAN branched structure allows a more uniform distribution of acetylene black with higher coatability, unlocking enhanced rate performances and efficient passivation of Ti-based oxides without the excessive electrolyte decomposition. These findings open a new way to design practical and durable sodium-ion batteries with a high-power density.

P2-type layered Na0.67Cr0.33Mg0.17Ti0.5O2 for Na storage applications.

Na0.67Cr0.33Mg0.17Ti0.5O2 with a P2-type layered structure has been synthesized and examined as a negative electrode material for rechargeable sodium batteries. The layered oxide delivers a reversible capacity of >90 mA h g-1, which corresponds to >95% of the theoretical capacity with excellent cyclability for >450 cycles.

Excess influx of Zn(2+) into dentate granule cells affects object recognition memory via attenuated LTP.

The influx of extracellular Zn(2+) into dentate granule cells is nonessential for dentate gyrus long-term potentiation (LTP) and the physiological significance of extracellular Zn(2+) dynamics is unknown in the dentate gyrus. Excess increase in extracellular Zn(2+) in the hippocampal CA1, which is induced with excitation of zincergic neurons, induces memory deficit via excess influx of Zn(2+) into CA1 pyramidal cells. In the present study, it was examined whether extracellular Zn(2+) induces object recognition memory deficit via excess influx of Zn(2+) into dentate granule cells. KCl (100 mM, 2 µl) was locally injected into the dentate gyrus. The increase in intracellular Zn(2+) in dentate granule cells induced with high K(+) was blocked by co-injection of CaEDTA and CNQX, an extracellular Zn(2+) chelator and an AMPA receptor antagonist, respectively, suggesting that high K(+) increases the influx of Zn(2+) into dentate granule cells via AMPA receptor activation. Dentate gyrus LTP induction was attenuated 1 h after KCl injection into the dentate gyrus and also attenuated when KCl was injected 5 min after the induction. Memory deficit was induced when training of object recognition test was performed 1 h after KCl injection into the dentate gyrus and also induced when KCl was injected 5 min after the training. High K(+)-induced impairments of LTP and memory were rescued by co-injection of CaEDTA. These results indicate that excess influx of Zn(2+) into dentate granule cells via AMPA receptor activation affects object recognition memory via attenuated LTP induction. Even in the dentate gyrus where is scarcely innervated by zincergic neurons, it is likely that extracellular Zn(2+) homeostasis is strictly regulated for cognition.

Construction of unmodified oligonucleotide-based microarrays in the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1: screening of the candidates for circadianly expressed genes.

DNA microarrays with unmodified oligonucleotide probes are a cost-effective and high-performance alternative to cDNA microarrays. We searched every gene in the genome of the thermophilic cyanobacterium Thermosynechococcus elongatus BP-1 for 45-mer oligonucleotide probes with optimal nucleotide sequences, and found such probes in 90% of the genes. Using the probes, we constructed a microarray that represented 2,397 genes (95% of total genes). We detected only low signals in the negative control probes whose nucleotide sequences are not contained in the T. elongatus genome, demonstrating that specific hybridization occurred. To evaluate the reliability of the measurements obtained by the oligonucleotide microarray, we performed microarray experiments using RNA samples from two different time points of circadianly synchronized cultures, LL2 (early sub-jective day) and LL14 (early subjective night). Measurements obtained from the two independent microarray hybridizations were highly concordant (correlation coefficient [r] > 0.8). Northern blot analyses of 20 genes confirmed that expression changes detected by the microarrays were correct (r = 0.832). We identified 143 candidate clock-controlled genes whose expression levels at LL2 and LL14 were significantly different. Expression of 69 of them was enhanced at LL14 while expression of the other 74 was enhanced at LL2. The physiological functions of the genes were diverse and included metabolism, translation, transcription, membrane transport, DNA replication and repair, and cell growth and death.

Global analysis of circadian expression in the cyanobacterium Synechocystis sp. strain PCC 6803.

Cyanobacteria are the only bacterial species found to have a circadian clock. We used DNA microarrays to examine circadian expression patterns in the cyanobacterium Synechocystis sp. strain PCC 6803. Our analysis identified 54 (2%) and 237 (9%) genes that exhibited circadian rhythms under stringent and relaxed filtering conditions, respectively. The expression of most cycling genes peaked around the time of transition from subjective day to night, suggesting that the main role of the circadian clock in Synechocystis is to adjust the physiological state of the cell to the upcoming night environment. There were several chromosomal regions where neighboring genes were expressed with similar circadian patterns. The physiological functions of the cycling genes were diverse and included a wide variety of metabolic pathways, membrane transport, and signal transduction. Genes involved in respiration and poly(3-hydroxyalkanoate) synthesis showed coordinated circadian expression, suggesting that the regulation is important for the supply of energy and carbon source in the night. Genes involved in transcription and translation also followed circadian cycling patterns. These genes may be important for output of the rhythmic information generated by the circadian clock. Our findings provided critical insights into the importance of the circadian clock on cellular physiology and the mechanism of clock-controlled gene regulation.

Roles of two ATPase-motif-containing domains in cyanobacterial circadian clock protein KaiC.

Cyanobacterial clock protein KaiC has a hexagonal, pot-shaped structure composed of six identical dumbbell-shaped subunits. Each subunit has duplicated domains, and each domain has a set of ATPase motifs. The two spherical regions of the dumbbell are likely to correspond to two domains. We examined the role of the two sets of ATPase motifs by analyzing the in vitro activity of ATPgammaS binding, AMPPNP-induced hexamerization, thermostability, and phosphorylation of KaiC and by in vivo rhythm assays both in wild type KaiC (KaiCWT) and KaiCs carrying mutations in either Walker motif A or deduced catalytic Glu residues. We demonstrated that 1) the KaiC subunit had two types of ATP-binding sites, a high affinity site in N-terminal ATPase motifs and a low affinity site in C-terminal ATPase motifs, 2) the N-terminal motifs were responsible for hexamerization, and 3) the C-terminal motifs were responsible for both stabilization and phosphorylation of the KaiC hexamer. We proposed the following reaction mechanism. ATP preferentially binds to the N-terminal high affinity site, inducing the hexamerization of KaiC. Additional ATP then binds to the C-terminal low affinity site, stabilizing and phosphorylating the hexamer. We discussed the effect of these KaiC mutations on circadian bioluminescence rhythm in cells of cyanobacteria.