[Effect of α7nAChR mediated cholinergic anti-inflammatory pathway on inhibition of atrial fibrillation by low-level vagus nerve stimulation].

Objective: To investigate the effect of α7nAChR mediated cholinergic anti-inflammatory pathway on inhibition of atrial fibrillation by low-level vagus nerve stimulation(LL-VNS). Methods: Eighteen beagles were randomized into control group (n=6), LL-VNS group (n=6) and methyllycaconitine (MLA) + LL-VNS group (n=6). All the beagles were subjected to rapid atrial pacing at 800 beats/min for 6 hours.And the effective refractory period (ERP) of atriums and pulmonary veins and induced atrial fibrillation (AF) were measured hourly during non-pacing.After cessation of pacing for 3 hours, the beagles in control group were injected with saline into four ganglionated plexis (GPs), the beagles in LL-VNS group were given LL-VNS and saline injected into four GPs, and the beagles in MLA+ LL-VNS group were injected with MLA into four GPs combined with LL-VNS.And the levels of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and acetylcholine (ACh) in the plasma at baseline condition, 3 h and 6 h were measured.At the end of this experiment, atrial tissues were collected to examine the levels of TNF-α, IL-6, ACh, NF-κBp65 and STAT3 proteins. Results: During the right atrium pacing for the first 3 hours, the ERPs were gradually decreased while AF inducibility were gradually increased in all groups. At the end of this experiment, compared with the control group and MLA+ LL-VNS group, the ERPs in LL-VNS group were increased, and the induced times and duration of AF were significantly decreased. The levels of TNF-α and IL-6 in plasma were all significantly decreased in LL-VNS group and MLA+ LL-VNS group when compared with the control group(pg/ml) [IL-6: (101±6) vs (119±7), P<0.05; (102±5) vs (119±7), P<0.05; TNF-α: (17.8±1.7) vs (22.1±2.0), P<0.05; (17.9±2.2) vs (22.1±2.0), P<0.05]. And the levels of ACh were higher than in the control group(µg/ml)[(151±13) vs (123±10), P<0.05; (145±5) vs (123±10), P<0.05]. After cessation of pacing for 6 hours, compared with the control groupand MLA+ LL-VNS group, the tissue levels of TNF-α and IL-6 were significantly decreased in LL-VNS group (P<0.05). The concentrations of NF-κBp65 proteins in atrial tissues were lower in the LL-VNS group (P<0.05), and the levels of STAT3 proteins in those tissues were higher in the LL-VNS group than in thein the two other groups (P<0.05). Conclusion: LL-VNS could inhibit the atrial electrical remodeling and atrial fibrillation induction; cholinergic anti-inflammatory pathway mediated by α7nAChR may be the important mechanism in vagal nerve regulated AF.

Simultaneous effects of surface spins: rarely large coercivity, high remanence magnetization and jumps in the hysteresis loops observed in CoFe2O4 nanoparticles.

Well-dispersed uniform cobalt ferrite nanoparticles were synthesized by thermal decomposition of a metal-organic salt in organic solvent with a high boiling point. Some of the nanoparticles were diluted in a SiO2 matrix and then the undiluted and diluted samples were characterized and their magnetic behavior explored. The undiluted and diluted samples exhibited maximum coercivity Hc of 23,817 and 15,056 Oe at 10 K, respectively, which are the highest values reported to date, and the corresponding ratios of remanence (Mr) to saturation (Ms) magnetization (Mr/Ms) were as high as 0.85 and 0.76, respectively. Interestingly, the magnetic properties of the samples changed at 200 K, which was observed in magnetic hysteresis M(H) loops and zero-field cooling curves as well as the temperature dependence of Hc, Mr/Ms, anisotropy, dipolar field, and the magnetic grain size. Below 200 K, both samples have large effective anisotropy, which arises from the surface spins, resulting in large Hc and Mr/Ms. Above 200 K, the effective anisotropy decreases because there is no contribution from surface spins, while the dipolar interaction increases, resulting in small Hc and Mr/Ms. Our results indicate that strong anisotropy and weak dipolar interaction tend to increase Hc and Mr/Ms, and also clarify that the jumps around H = 0 in M(H) loops can be attributed to the reorientation of surface spins. This work exposes the underlying mechanism in nanoscale magnetic systems, which should lead to improved magnetic performance.

Tuning the transport properties of a (C60)2 bridge with electron and hole dopings.

The tuning effects of substitutional B and N dopings on the electron transport properties of a C(60) dimer bridge [(C(60))(2)] are investigated by nonequilibrium Green's functions in combination with density functional theory. It is found that, unlike C(60), the equilibrium conductance of (C(60))(2) is very small. However, it can be controlled by electron (N) doping or hole (B) doping, which shifts the molecular energy levels so that the LUMOs or HOMOs align well with the Fermi level and results in LUMO-mediated transport or HOMO-mediated transport. The conductance increases accordingly with a certain number of N or B atoms doped in the C(60)s. Interestingly, when one C(60) is doped with N atoms and the other is doped with B atoms, new transport behaviors arise and rectification is achieved due to the special alignment of the energy levels of the individual C(60)s with the Fermi level. It suggests that cluster or molecule assembling can often realize specific functions which are not available by single molecules and should be taken into consideration in the design of molecular devices.

Ab initio electron transport study of carbon and boron-nitrogen nanowires.

We report first-principles calculations on the electrical transport properties of two kinds of one-dimensional nanowires: (a) a carbon nanowire (CNW) with alternating single and triple bonds and (b) a boron-nitrogen nanowire (BNNW) with equidistant bonds. We demonstrate the similarity and difference between the carbon nanowire and its boron-nitrogen analogue in the molecular orbital and transport properties, and then explore the potential innovations. The effects of molecular orbitals and nanowire-electrode coupling on the transport properties are analyzed. The cases of the nanowires sandwiched between both nanoscale and bulk electrodes are considered. It suggests that the characteristics of the transmission spectra and the current-voltage characteristics (I-V curves) are determined both by the electrodes and by the molecule as well as their coupling. In particular, the negative differential resistance (NDR) phenomenon is more apparent when the nanowires are positioned between two nanoscale electrodes. The tuning of the transport properties is also probed through the changes of nanowire-electrode separation and the inclusion of a gate voltage. These lead to dramatic variations in the equilibrium conductance, which can be understood from the shift and alignment of the molecular orbital relative to the Fermi level of the electrodes. In the analysis of the effects of nanowire-electrode separation, it shows that the equilibrium conductance has the same variation behavior as that of the projected density of states (PDOS) for CNW, while the localized molecular orbitals of BNNW result in its conductance varies differently from its PDOS. The different molecular orbital characteristics near the Fermi level of these two kinds of nanowires underlie their different transport properties.

The perioperative use of ceftriaxone as infection prophylaxis in neurosurgery.

An open label study was conducted in the department of neurosurgery, Beijing Tiantan Hospital in China to determine the incidence of postoperative infections following the use of one or two doses of ceftriaxone administered perioperatively. A total of 343 patients, who required neurosurgery and had satisfied the inclusion criteria, was recruited during a 12 month study period. Of these 343 patients, there were 97 and 107 cases of malignant and benign tumours, respectively, 52 cases of aneurysm, 34 cases of arteriovenous malformation, and 53 other cases who underwent neurosurgery for drainage of sub-dural haematoma, relief of cerebral oedema and other indications. A total of 6 (1.75%) cases of postoperative infection was observed, of which 4 were found in the malignant tumour group, and 2 in the arteriovenous malformation group. All six patients were suffering from meningitis. During the 12 month period immediately prior to the present study, when postoperative penicillin and gentamicin was administered twice daily for 5-7 days as regular prophylaxis against infection, the incidence of postoperative infection was 7.2% in the same department managed by the same staff. Results of our present study suggest that one to two doses of ceftriaxone administered perioperatively are effective in reducing the rate of postoperative infections.

Effects of nimodipine, felodipine, and verapamil on isolated human arteries.

AIM: To evaluate whether there might be some difference in the action modes of nimodipine (Nim) and felodipine (Fel). METHODS: Compare the inhibitory effects of Nim and Fel with that of verapamil (Ver) as a representative of phenylalklamine on norepinephrine (NE)- and CaCl2-evoked contractions of human arteries. RESULTS: In Ca(2+)-free and high K+ depolarized solution, inhibitory effects of Nim, Fel, and Ver were more potent on CaCl2-induced contractions on isolated human arteries than those on NE-induced contractions. In CaCl2-induced contraction, the pD2 values for Nim, Fel, and Ver were 7.5, 7.42, 6.35 on uterine arteries; 7.38, 7.65, 7.20 on mesenteric arteries and 7.87, 9.10, 7.32 on renal arteries, respectively. Ver inhibited 2 components of NE-evoked contraction, while Nim and Fel only inhibited extracellular Ca(2+)-dependent contractions. CONCLUSION: The result indicates that Fel has a selective action on human renal arteries.