Role of CaMKII and PKA in early afterdepolarization of human ventricular myocardium cell: A Computational model study

Early afterdepolarization (EAD) plays an important role in arrhythmogenesis. Many experimental studies have reported that Ca2+/calmodulin-dependent protein kinase II (CaMKII) and β-adrenergic signaling pathway are two important regulators. In this study, we developed a modified computational model of human ventricular myocyte to investigate the combined role of CaMKII and β-adrenergic signaling pathway on the occurrence of EADs. Our simulation results showed that () CaMKII overexpression facilitates EADs through the prolongation of late sodium current’s () deactivation progress; () the combined effect of CaMKII overexpression and activation of β-adrenergic signaling pathway further increases the risk of EADs, where EADs could occur at shorter cycle length (2000 ms versus 4000 ms) and lower rapid delayed rectifier K+ current () blockage (77% versus 85%). In summary, this study computationally demonstrated the combined role of CaMKII and β-adrenergic signaling pathway on the occurrence of EADs, which could be useful for searching for therapy strategies to treat EADs related arrhythmogenesis

Cascaded channel estimation technique for massive MIMO relay system

© Published under licence by IOP Publishing Ltd. This paper concerns with the cascaded channel estimation of massive multiple-input multiple-output (MIMO) relay system. In order to meet the increasing demands for high-speed wireless communication networks, massive MIMO has been recognized as one of the key technologies for the future fifth generation (5G) cellular networks. It is an advanced MIMO technique consists of a very large number of antennas at the base station and serves a smaller number of single-antenna users simultaneously. Basically, the idea of massive MIMO technique is to harvest all the advantages of conventional MIMO system in a much larger scale. To reap the benefits of massive MIMO in practice, an accurate estimation of the channel state information (CSI) is needed. In this paper, the relaying technique has been incorporated with massive MIMO system in order to increase system throughput and improve the coverage in cell-edge users. A relay node is placed in between transmitter and receiver to reduce the path loss and improve the spectral efficiency of massive MIMO system. Cascaded channel estimation technique for massive MIMO relay system is developed in this paper. The mean squared error (MSE) of the cascaded channel estimation for massive MIMO relay sytem is optimized to obtain accurate CSI

Peptide-protein Interactions: Photoinduced Electron-transfer Within The Preformed And Encounter Complexes Of A Designed Metallopeptide And Cytochrome C

Photoinduced electron-transfer (ET) occurs between a negatively charged metallopeptide, [Ru(bpy)2(phen-am)-Cys-(Glu)(5)-Gly](3-) = RuCE(5)G, and ferricytochrome c = Cyt c. In the presence of Cyt c, the triplet state lifetime of the ruthenium metallopeptide is shortened, and the emission decays via biexponential kinetics, which indicates the existence of two excited-state populations of ruthenium peptides. The faster decay component displays concentration-independent kinetics demonstrating the presence of a preformed peptide-protein complex that undergoes intra-complex electron-transfer. Values of K-b = (3.5 +/- 0.2) x 10(4) M-1 and k(ET)(obs) = (2.7 +/- 0.4) x 10(6) s(-1) were observed at ambient temperatures. The magnitude of k(ET)(obs) decreases with increasing solvent viscosity, and the behavior can be fit to the expression k(ET)(obs) proportional to eta(-alpha) to give alpha = 0.59 +/- 0.05. The electron-transfer process occurring in the preformed complex is therefore gated by a rate-limiting configurational change of the complex. The slower decay component displays concentration-dependent kinetics that saturate at high concentrations of Cyt c. Analysis according to rapid equilibrium formation of an encounter complex that undergoes unimolecular electron transfer yields K-b\u27 = (2.5 +/- 0.7) x 10(4) M-1 and k(ET)(obs) = (7 +/- 3) x 10(5) s(-1). The different values of k(ET)(obs) and k(ET)(obs) suggest that the peptide lies farther from the heme when in the encounter complex. The value of k(ET)(obs) is viscosity dependent indicating that the reaction occurring within the encounter complex is also configurationally gated. A value of alpha = 0.98 +/- 0.14 is observed for k(ET)(obs), which suggests that the rate-limiting gating processes in the encounter complex is different from that in the preformed complex

Crystal structure of 3-methyl-2-oxo-2H-chromen-7-yl propionate, C13H12O4

Abstract C13H12O4, triclinic, P1̄ (no. 2), a = 6.141(5) Å, b = 8.108(6) Å, c = 12.234(9) Å, α = 79.257(12)°, β = 76.820(12)°, γ = 74.687(11)°, V = 566.8(7) Å3, Z = 2, R gt(F) = 0.0515, wR ref(F 2) = 0.1575, T = 296(2) K

(25R)-5a-Spiro­stane-3,12-dione

The title compound, C27H40O4, was obtained from the oxidation of (25R)-3b-hydr­oxy-5a-spiro­stan-12-one (Hecogenin) by Jone’s reagent. The mol­ecule contains six alicyclic and heterocyclic rings, all trans-fused, among which four six-membered rings adopt similar chair conformations while two five-membered rings assume an envelope conformation

Evaluation of a GNSS for wave measurement and directional wave spectrum analysis

Wave buoys are important devices to monitor and analyze wave data for ocean and coastal engineering. A GNSS wave buoy is briefly introduced in the paper, which has high resolution to measure the buoy motion by vertical, north-south and west-east displacements and independent velocities in above three directions. Based on the displacements and velocities, statistical results, frequency spectra and directional spectra are analyzed, and results based on the displacements are compared with that from Waverider with a distance less than 6m deployed in the special sea water with the GNSS buoy. Wave profiles comparison show that GNSS buoy presented slightly large significant wave height and mean wave height due to its high sampling frequency, and resulted in smaller mean wave period than that from Waverider. Statisticaly, between the analyzing result of the GNSS and wave rider, the maximum error of wave height is about 5.5%; and the maximum difference of wave period is about 0.5s, when sampling frequency is similar. The energy spectra were basically consistent from these two devices. The peaks of directional spectra were similar but the spreading angle was smaller from GNSS. Results mean the GNSS device presents almost similar wave information to that from Waverider.</p

Exploring Impaired SERCA Pump-Caused Alternation Occurrence in Ischemia

Impaired sarcoplasmic reticulum (SR) calcium transport ATPase (SERCA) gives rise to Ca(2+) alternans and changes of the Ca2+release amount. These changes in Ca(2+) release amount can reveal the mechanism underlying how the interaction between Ca(2+) release and Ca(2+) uptake induces Ca(2+) alternans. This study of alternans by calculating the values of Ca(2+) release properties with impaired SERCA has not been explored before. Here, we induced Ca(2+) alternans by using an impaired SERCA pump under ischemic conditions. The results showed that the recruitment and refractoriness of the Ca(2+) release increased as Ca(2+) alternans occurred. This indicates triggering Ca waves. As the propagation of Ca waves is linked to the occurrence of Ca(2+) alternans, the "threshold" for Ca waves reflects the key factor in Ca(2+) alternans development, and it is still controversial nowadays. We proposed the ratio between the diastolic network SR (NSR) Ca content (Cansr) and the cytoplasmic Ca content (Ca i ) (Cansr/Ca i ) as the "threshold" of Ca waves and Ca(2+) alternans. Diastolic Cansr, Ca i , and their ratio were recorded at the onset of Ca(2+) alternans. Compared with certain Cansr and Ca i , the "threshold" of the ratio can better explain the comprehensive effects of the Ca(2+) release and the Ca(2+) uptake on Ca(2+) alternans onset. In addition, these ratios are related with the function of SERCA pumps, which vary with different ischemic conditions. Thus, values of these ratios could be used to differentiate Ca(2+) alternans from different ischemic cases. This agrees with some experimental results. Therefore, the certain value of diastolic Cansr/Ca i can be the better "threshold" for Ca waves and Ca(2+) alternans

Evaluation of a GNSS for wave measurement and directional wave spectrum analysis

Wave buoys are important devices to monitor and analyze wave data for ocean and coastal engineering. A GNSS wave buoy is briefly introduced in the paper, which has high resolution to measure the buoy motion by vertical, north-south and west-east displacements and independent velocities in above three directions. Based on the displacements and velocities, statistical results, frequency spectra and directional spectra are analyzed, and results based on the displacements are compared with that from Waverider with a distance less than 6m deployed in the special sea water with the GNSS buoy. Wave profiles comparison show that GNSS buoy presented slightly large significant wave height and mean wave height due to its high sampling frequency, and resulted in smaller mean wave period than that from Waverider. Statisticaly, between the analyzing result of the GNSS and wave rider, the maximum error of wave height is about 5.5%; and the maximum difference of wave period is about 0.5s, when sampling frequency is similar. The energy spectra were basically consistent from these two devices. The peaks of directional spectra were similar but the spreading angle was smaller from GNSS. Results mean the GNSS device presents almost similar wave information to that from Waverider.</p

The effects of dietary fiber level on nutrient digestibility in growing pigs

The objective of this study was to investigate the effects of total dietary fiber level on nutrient digestibility and the relationship between apparent total tract digestibility of total dietary fiber, and soluble dietary fiber, insoluble dietary fiber and available energy. Sugar beet pulp was as the only fiber source. The experiment was designed as a 6 × 6 Latin square with an adaptation period of 7 d followed by a 5-d total collection of feces and urine. Feed intake tended to decrease (P =0.10) as total dietary fiber level increased. The apparent total tract digestibility of dry matter, crude protein and gross energy decreased (P <0.01) when total dietary fiber increased but the digestibility of soluble dietary fiber and insoluble dietary fiber increased (P <0.01). The digestible energy and metabolizable energy content of diets decreased (P <0.01) as the total dietary fiber increased