Monophasic stimulation

To guarantee safety, a capacitor is placed at the output terminal of the electronics. In the event of electronics failure, in which the output is shorted to one of the supply voltages, the output capacitor is crucial in preventing a continuous DC charge injection. The output capacitor is also useful in implementing charge balance, as can be seen in the monophasic stimulation example (Section 4.3). 

Figure 4 is one of the illustrations from a recent publication by Euler. After the administration of an adrenolytic agent, Dibenamine, the pressor effect of adrenaline was in large measure reversed whereas the pressor response to corresponding increments of l-noradrenaline and to extracts of spleen or splenic nerve remained upright and monophasic. In general the effect of hepatic nerve stimulation is not affected by amounts of adrenolytic agents that will reverse the response to epinephrine (48, 75,163). 

In non-CF HBE, forskolin stimulated a large, biphasic increase in Cl" secretion, whereas the response in AF508-HBE was monophasic and <5% of the wild-type response. The forskolin response in non-CF and AF508-HBE is blocked by CFTR inhibitors but not the Ca2+-activated Cl" channel blocker, DIDS, indicating that the response is due to CFTR activity in the apical membrane. Residual AF508-CFTR activity in the apical membrane of CF airway... 

The muscle is stimulated with a monophasic rectangular stimulus of 3 ms duration and at 1.5 times the stimulation threshold using a 1831A stimulator... 

Temuujin J., Okada K., Mackenzie K.J.D. Characterization of aluminosilicate (mullite) precursors prepared by mechanochemical process. J. Mat. Res. 1998 13 2184-88. Temuujin J., Jadambaa T.S., Okada K., Mackenzie K.J.D. Preparation of aluminosilicate precursor by silica mixtures. Bull. Mat. Sci. 1998 21 185-87. Karagedov G.R.,Liubuschko G.l. Mechanochemically stimulated synthesis of monophase mullite. Chem. Sustainable Development 1998 6 161-63. 

Contractions are usually evoked by applying 0.5-s trains of pulses of 110% maximal voltage (train frequency 0.1 Hz pulse frequency 5 Hz pulse duration 0.5 ms) (see Note 4 and Table 2 for more details). The amplitude of each monophasic contraction so induced appears to be determined more by released ATP than noradrenaline (Subheading 1.), as we have found that twitch amplitude is attenuated to a significantly greater extent by PPADS (a P2 receptor antagonist) than by prazosin (an ai-adrenoceptor antagonist) (12). Different stimulation conditions have been described by another laboratory (see Note 5). 

FIGURE 30.5 Action potential initiation by extracellular stimulation of CNS neurons by cathodic and anodic stimuli. Each trace shows transmembrane voltage as a function of time for different sections of the neuron, (a) Stimulation with a monophasic cathodic stimulus pulse from an electrode positioned f mm over a node of Ranvier of the axon. Depolarization occurs in the node directly beneath the elertrode (solid arrowhead) and hyperpolarization occurs in the adjacent nodes of Ranvier (open arrowhead). Action potential initiation occurs in the node of Ranvier directly under the electrode (arrow) and the action potential propagates in both directions, (b) During threshold stimulation with an electrode positioned 1 mm over the cell body, action potential initiation occurs at a node of Ranvier of the axon. With cathodic stimuli (duration 0.1 msec) action potential initiation occurred at the second node of Ranvier from the cell body (arrow), (c) With anodic stimuli (duration 0.1 msec) action potential initiation occurred in the third node of Ranvier from the cell body (arrow). 

The electrical incremental and desynchronizing responses are elicited by unilateral electrical stimulation through adjacent electrode contacts (where the cathode was always the lower contact). Stimuli consist of 5 to 30 sec trains of monophasic square pulses of 1.0 msec duration and 6- to 60-Hz frequency. Analysis of the scalp distribution of the incremental spike-wave and desynchronizing electrocortical responses is made from EEG recordings taken from frontopolar (FP2, FPl), frontal (F4, F3), central (C4, C3), parietal (P4, P3), occipital (02, Ol), frontotemporal (F8, F7), and anterior temporal (T4,T3) referred to ipsilateral ears (A2, Al) (Sensitivity = 10 /xA/cm time constant = 0.35 sec paper speed = 15 mm/sec). 

The pulses may be of unidireetional eurrent (interrupted DC, monophasic), which implies that the current has a DC component. High-voltage pulsed galvanic stimulation is also used, with pulse currents up to some amperes, but pulse duration only a few microseconds. If DC effects are to be avoided (e.g., to reduce electrolytic effects or electrode metal corrosion), the current is biphasic. Faradic currents are biphasic currents of the type generated by an induction coil. If the pulses are slowly increased in amplitude, then reduced, and after a pause again increased, we have a ramp or surged current. Because many effects are current controlled, it is often better to use a constant amplitude current mode than a constant amplitude voltage mode of the stimulator output. 

In vivo phagocytosis of isolated peritoneal macrophages of mice and macrophages of the isolated perfunded rat liver have been stimulated by i.p. injection or oral application of . purpurea expressed sap [138]. By low concentrations of expressed sap, an induction of TNF, IL-1 and IL-6 secretion has been observed [134, 135]. After application of 1 ml/kg b.w. to rabbits, a cold-defense-reaction has been described as a cytokine-mediated effect. Body temperature raised monophasic by 1° C after a lag time of 30 min [139]. 

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