Current stimulators

Viereck V, Grundker C, Blaschke S, Niederkleine B, Siggelkow H, Frosch KH, Raddatz D, Emons G, Hofbauer LC (2003) Raloxifene con currently stimulates osteoprotegerin and inhibits interleukin-6 production by human trabecular osteoblasts. J Clin Endocrinol Metab 88 4206-4213... 

Chemistry receives a lot of its current stimulation from its two-way trafficking with the biological world. Three essays under the heading Biological Aspects in Section IV (p 339) serve to illustrate this point extremely well. 

Action duration of GABAa opening, leading to CP current Stimulates GABA inhibits NMDA Inhibits NMDA and opioid n receptors (stimulates k, and S) Stimulates GABA... 

P. R. Supronowicz, P. M. Ajayan, K. R. Ullmann, B. P. Arulanandam, D. W. Metzger, R. Bizios, Novel current-conducting composite substrates for exposing osteoblasts to alternating current stimulation, Journal of Biomedical Materials Research, vol. 59, pp. 499-506, 2002. 

A term used to describe how easily a metal is oxidized is active. A more active metal is one that is more easily oxidized. A listing of metals in order of activity is known as an activity series. The activity series is used to determine which substances will be oxidized and reduced in an electrochemical cell the element higher on the list will be oxidized. For example, in a cell with aluminum and silver electrodes in their appropriate solutions, aluminum is oxidized and silver is reduced. Therefore, aluminum is the anode and silver is the cathode. If you have ever bitten a piece of aluminum foil and experienced discomfort, you had this electrochemical process occur in your mouth. Silver (or mercury) fillings and the aluminum serve as electrodes and your saliva serves as an electrolyte between the two. The resulting current stimulates the nerves in your mouth resulting in the discomfort. 

Figure 4 Electrically evoked single-unit tactile responses recorded with microwire multielectrode arrays in rat hippocampus CA1, primary somatosensory cortex, and ventral posteromedial nucleus brain regions. (Upper) Raster plot of single-unit spikes before and after electrical current stimulation to whiskers. Each row is a separate trial. (Lower) Summed activity for all trials in 1-ms bins that demonstrate a response to electrical stimulation. The graphs show different latencies in firing for the three different regions. [Data reprinted from Ref. (1 3). Copyright (2007) National Academy of Sciences, U.S.]...

Anyone who bites a piece of aluminum foil (such as that used for wrapping candies) in such a way that the foil presses against a dental filling will probably experience a momentary sharp pain. In effect, an electrochemical cell has been created in the mouth, with aluminum (P = -1.66 V) as the anode, the filling as the cathode, and saliva as the electrolyte. Contact between the aluminum foil and the filling short-circuits the cell, causing a weak current to flow between the electrodes. This current stimulates the sensitive nerve of the tooth, causing an unpleasant sensation. 

A quantum-mechanical theory of interaction of intense s ubpicosecond laser pulse with the single-wall CN has been presented in this paper. Spectrum of the induced current has been calculated. It represents the superposition of narrow discrete lines and continuous background. Presence of continuous background makes impossible to observe harmonics of the order higher then N=25-i-31. Moreover, the interference of currents stimulated by inter- and intraband transitions lead to the reduction of the effectiveness of HHG in comparison with the semiclassical model [1,2]. 

When implantable electrodes are used for direct current stimulation of bone growth, current density levels of 0.1-0.5 mA/cm of geometric electrode area appear to be effective. Above the 0.5 mA/cm level, cell damage occurs. Below 0.1 mA/cm, stimulation is ineffective. Unfortunately, little if anything... 

Bourland, J. D., J. A. Nyenhuis, G. A. Mouchawar, L. A. Geddes, D. J. Schaefer, and M. E. Riehl, 1991, Z-Gradient Coil Eddy-Current Stimulation of Skeletal and Cardiac Muscle in the Dog, Book of Abstracts, Society of Magnetic Resonance in Medicine, Tenth Annual Meeting, San FraiKisco, p. 969. 

Paterson DC, Lewis GN, Cass CA (1980) Treatment of delayed union and non-union with an implanted direct current stimulator. Clin Orthop Relat Res 148 117-128... 

The first reported use of CNTs as an osteogenic biomaterial was in 2002 by Supronowicz et al. [41]. To promote ceU growth and adhesion, MWCNTs were incorporated into a PLA to fabricate conductive PLA/MWCNT nanocomposites. Osteoblast cells were seeded onto the surface and then exposed to alternating current stimulation (10 micro A at 10 Hz). Their results showed an increase in osteoblast proliferation by 46% after 2 days and increased extracellular calcium by 307% after 21 consecutive days. 

With the advent of advanced electronics and computerization, electrochemical techniques have evolved rapidly. The most common technologies today are the polarization resistance technique, electrochemical impedance, and Tafel extrapolation. Regardless of the technique used, each relies on the same basic principles in each test, a metallic coupon in an electrolyte is subject to an electrical perturbation. This perturbation is the appUcation of a current from an external source (power supply). This current stimulates the surface corrosion reactions. The voltage (potential) response of the coupon is measured and correlated with the current appUed—a galvanodynamic test. Conversely, the coupon potential is controlled and correlated with the requisite current—a potentiodynamic test. In either case, the resultant current is representative of the rate determining mass transfer or charge transfer rate. This may be related to the corrosion rate. 

Salman, N. N., The Effect of Direct Electrical Current Stimulation on the Bone Growth into Porous Polymeric, Ceramic and Metallic Implants, Ph.D. thesis, Clemson University, 1980. 

To be exact, when the current stimulates the phase growth, nonequihbrium vacancies reduce this augmentation (opposing the growth) if the current inhibits the phase growth, nonequihbrium vacancies reduce this suppression (promoting the growth). 

What happens is this the aluminum and the dental filling act as electrodes in a galvanic cell. Aluminum acts as the anode, and the amalgam acts as the cathode. In effect, when the aluminum comes into contact with the amalgam, an electrochemical cell is established in the mouth, causing a current to flow. This current stimulates the nerve of the tooth, causing a very unpleasant sensation. 

B. Effects of increasing extracellular a in the cuneate. Changes in presynaptic excitability and in the efficiency of synaptic transmission were measured by constant current stimulation via a third micro-electrode, attached near the ion-exchanger and reference electrodes. Direct stimulation of the afferent fibres near their terminals evokes antidromic responses in forelimb nerves (see R, Fig. 9) which provide an index of the number of fibres excited and thus of the excitability of the afferent terminals (Wall, 1958). At the same time, orthodromic trans-synaptic responses are evoked which can be recorded from the medial lemniscus (R2, Fig. 9). These antidromic and orthodromic responses thus represent the input and output of the cuneate, and therefore give an indication of the efficiency of synaptic transmission through the nucleus. 

B. Integrated antidromic potentials recorded from peripheral forelimb nerve in response to cycles of automatically incremented constant current stimulation of fibre terminals via third micro-electrode attached to K electrode. KCl (0.1 M) injected from fourth micro-pipette 100 ym away during time marked by horizontal black bar. 

Supronowicz, PR. et al. Novel current-conducting composite substrates for exposing osteoblasts to alternating current stimulation. J. Biomed. Mater. Res., 59,499,2002. 

Fig. 3 The circuit diagram of the constant current stimulator. Because of AD8801 only has positive output, and the stimulate pulse is biphasic...

The constant-current micro-stimulator was verified by varying the load. The relationship between voltage outputs under varied load is shown in Fig. 5. We can observe that the constant current stimulation can be operated at load below 15 kQ. 

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