Pathophysiological roles of G-protein-coupled receptor kinases

In the past two decades, a plethora of information has accumulated on β-adrenoceptor (AR)2 functional expression in both normal cardiac physiology and disease. The paradigm of this expression is that catecholamine binding to the β-AR on the cell surface initiates a cascade of intracellular

Regulation of β-Adrenoceptor Signaling in Cardiac Function and Disease

Differential functional expression of human myocardial G protein receptor kinases in left ventricular cardiac diseases.

https://iopscience.iop.org/article/10.1088/1361-6463/aacf10/pdf

Low-pressure discharges with hollow cathode and hollow anode and their applications

Background— Past studies have suggested that the adrenergic system becomes abnormally activated in chronic volume overload, such as in severe aortic valve regurgitation (AR). However, the effectiveness of agents directed against this adrenergic activation has never been adequately tested in chronic AR. We therefore tested the effects of metoprolol treatment on the left ventricular (LV) function and remodeling in severe chronic AR in rats. Methods and Results— Severe AR was created in adult male Wistar rats by retrograde puncture of the aortic leaflets under echocardiographic guidance. Two weeks later, some animals received metoprolol treatment (25 mg/kg) orally for 24 weeks, and some were left untreated. LV dimensions, ejection fraction, and filling parameters were evaluated by echocardiography. Hearts were harvested at 1, 2, 14, and 180 days for the evaluation of hypertrophy, β-adrenergic receptor status, and extracellular matrix remodeling. We found that metoprolol treatment prevented LV dilatation and ...

Effectiveness of β-Blockade in Experimental Chronic Aortic Regurgitation

The use of fresh autologous pericardium in valve surgery has shown poor results in the past mainly due to thickening and retraction. Recently, it has been suggested that a short treatment with glutaraldehyde might radically change its behavior. In an attempt to determine whether this disparity in results is due to the glutaraldehyde treatment or to a better present-day surgical technique, fresh and glutaraldehyde-treated autologous pericardium was mounted in a frame and implanted in the pulmonary position of adult sheep. Six survivors obtained in each group were sacrificed between 2 and 8 months in the "fresh" group and between 2 and 6 months in the "glutaraldehyde-treated" group. Macroscopically, the fresh pericardium became thickened and retracted in all specimens, eventually resulting in severe regurgitation, while the glutaraldehyde-treated, although slightly thickened, retained its pliability without significant retraction. Microscopically, viability of the central core of the collagen was more often preserved in the fresh pericardium. Endothelialization was irregular. In conclusion, short glutaraldehyde treatment seems to improve the results of autologous pericardium mounted on a valve stent. Its effect on calcification remains to be ascertained.

Comparison of Fresh and Glutaraldehyde-Treated Autologous Stented Pericardium as Pulmonary Valve Replacement

The pseudospark (PS) discharge has been shown to be a promising source of high brightness, high intensity electron beam pulses. The PS discharge sourced electron beam has potential applications in plasma filled microwave sources where normal material cathode cannot be used. Analysis of the electron beam profile has been done experimentally for different applied voltages. The investigation has been carried out at different axial and radial location inside the drift space in argon atmosphere. This paper represents experimentally found axial and radial variation of the beam current inside the drift tube of PS discharge based plasma cathode electron (PCE) gun. With the help of current density estimation the focusing and defocusing point of electron beam in axial direction can be analyzed.

Experimental Analysis of Pseudospark Sourced Electron Beam

The Pseudospark switch is able to control high voltage and high current discharges and operates at low pressure like Thyratron but much simpler in construction and does not suffer in electrodes wear. This switch is bipolar and has 100 % reverse current capability, much faster than Thyratron and has applications in pulse power modulators, linear accelerators, laser systems etc. Such switch has been developed at CEERI Pilani and tested in a demountable setup. For this switch, as a cold cathode based ferroelectric trigger source has also been developed and characterized. High dielectric material has been opted for such a source. The hold off voltage can be doubled if the gap of the electrodes is stacked to two single stage gaps. Such stack of two single stage switches has also been fabricated in a demountable setup. Switching behavior has been observed up to 23 kV and 7 kA in single stage. High voltage conditioning and characterization is still in progress. The paper includes the introduction with working principle, description of the demountable set up, simulation by TriComp, AMaze and OOPIC Pro (Without Comparison among them), and switching behavior.

https://iopscience.iop.org/article/10.1088/1742-6596/208/1/012110/pdf

Characterization of High Power Pseudospark Plasma Switch (PSS)

Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using two coaxial quartz double barrier DBD tubes, which are filled with Xe/Ar at different pressures. A sinusoidal voltage up to 2.4 kV peak with frequencies from 20 to 100 kHz has been applied to the discharge electrodes for the generation of microdischarges. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. By comparisons of visual images and electrical waveforms, the filamentary discharges for Ar tube while homogeneous discharge for Xe tube at the same conditions have been confirmed. The electrical modeling has been carried out to understand DBD phenomenon in variation of applied voltage waveforms. The simulated discharge characteristics have been validated by the experimental results.

https://iopscience.iop.org/article/10.1088/1742-6596/208/1/012142/pdf

M. Kumar

Papers

Comparison of Fresh and Glutaraldehyde-Treated Autologous Stented Pericardium as Pulmonary Valve Replacement

Experimental Analysis of Pseudospark Sourced Electron Beam

Characterization of High Power Pseudospark Plasma Switch (PSS)

Discharge analysis and electrical modeling for the development of efficient dielectric barrier discharge

Comparison of the effect of left ventricular volume and pressure overload on β-adrenoceptor density in left heart valvular disease