Long-term vascular access ports as a means of sedative administration in a rodent fMRI survival model

The purpose of this study is to develop a rodent functional magnetic resonance imaging (fMRI) survival model with the use of heparin-coated vascular access devices. Such a model would ease the administration of sedative agents, reduce the number of animals required in survival experiments and eliminate animal-to-animal variability seen in previous designs. Seven male Sprague-Dawley rats underwent surgical placement of an MRI-compatible vascular access port, followed by implantable electrode placement on the right median nerve. Functional MRI during nerve stimulation and resting-state functional connectivity MRI (fcMRI) were performed at times 0, 2, 4, 8 and 12 weeks postoperatively using a 9.4 T scanner. Anesthesia was maintained using intravenous dexmedetomidine and reversed using atipamezole. There were no fatalities or infectious complications during this study. All vascular access ports remained patent. Blood oxygen level dependent (BOLD) activation by electrical stimulation of the median nerve using implanted electrodes was seen within the forelimb sensory region (S1FL) for all animals at all time points. The number of activated voxels decreased at time points 4 and 8 weeks, returning to a normal level at 12 weeks, which is attributed to scar tissue formation and resolution around the embedded electrode. The applications of this experiment extend far beyond the scope of peripheral nerve experimentation. These vascular access ports can be applied to any survival MRI study requiring repeated medication administration, intravenous contrast, or blood sampling

Zinc Oxidation in Dilute Alkaline Solutions Studied by Real-Time Electrochemical Impedance Spectroscopy

Electrochemical oxidation of zinc has been studied in dilute alkaline solutions, 0.010 and 0.10 M KOH, employing cyclic voltammetric and real-time Fourier transform electrochemical :Impedance spectroscopy (FTEIS) experiments. Thermodynamic analysis of cyclic voltammetric data indicates that Zn(OH)(4)(2-) is produced as a major product in both 0.10 and 0.010 M KOH although ZnO/Zn(OH)(2) may also be produced as a minor product in 0.010 M. A large body of impedance data was obtained as a function of swept potential by running combined staircase cyclic voltammetry and FTEIS (SCV-FTEIS) experiments at every 10 mV and 200 ms interval, which allowed a systematic and complete analysis to be made on the interface. Analysis of the extensive impedance data demonstrates that electron transfer takes place across the thin oxide/hydroxide film, whose electrical state undergoes drastic changes at the potential where charge transfer occurs. The capacitance of the film covering the surface was shown to undergo a large change during the charge transfer indicating that the electrode/electrolyte interface is strongly electrified during the charge transfer across it. Various electrode reaction kinetic parameters for oxidation of zinc are also reported by treating the impedance data and the reaction mechanism is discussed based on the data.close101