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Query: UMLS:C0403608 (ureter)
 9,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In Sodium-deficient solutions both the electrical and mechanical activity of the ureter are reduced. The plateau component of the action potential in the smooth muscle cell of the guinea pig ureter is more affected than the oscillations. Tetrodotoxin, which blocks the action potential in nerves, does not influence activity or conduction in the ureter. This is an important argument for the myogenic conduction of activity in this tissue.
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PMID:The influence of sodium on the electrical and mechanical activity of the ureter. 120 91

1. The membrane properties of the guinea-pig ureter were studied in physiological Krebs solution by intra- and extracellular stimulating methods.2. The mean membrane potential was 50 mV. Action potentials triggered by external stimulation were composed of repetitive spikes and a plateau phase.3. The effects of intracellular polarization on the membrane activity elicited by extracellular stimulation were observed. Anodal polarization enhanced the amplitude and the maximum rate of rise of the spike while cathodal polarization reduced them. The number of the spikes, the duration and amplitude of the plateau phase were not changed by polarization of any direction.4. The spikes triggered by intracellular stimulation were mostly graded, but repetitive spikes sometimes continued even after cessation of the stimulation. The effective membrane resistance was 15-23 MOmega and the time constant was 2-3 msec.5. Conduction velocity (V), chronaxie, time constant (tau) and space constant (lambda) of the tissue were measured by extracellular stimulation. These values were as follows: V, 3-6 cm/sec; chronaxie, 20-40 msec; tau, 200-300 msec; lambda, 2.5-3 mm. The conduction of excitation might be related to the cable properties of the tissue.6. The relative refractory period measured by extracellular stimulation was as long as 30 sec. During the relative refractory period dissociation of the slow depolarization and the spikes was observed by successive stimuli.7. The plateau phase was prolonged and the frequency of the spontaneous discharges was increased by treatment with Ba(2+). Tetrodotoxin had no effect on spike activity nor on the plateau phase, but Mn(2+) blocked the membrane activity.
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PMID:Membrane properties of the smooth muscle of guinea-pig ureter. 605 Jan 2

The guinea-pig ureter was placed in a three-compartment organ bath to enable the application of electrical stimuli or drugs to its renal end (R-site), the middle region (M-site) or the bladder end (B-site) while recording mechanical activity at the R- and B-sites. All experiments were performed in ureters pre-exposed to capsaicin (10 microM for 15 min) to prevent the release of sensory neuropeptides from afferent nerves. Electrical field stimulation (EFS, 5-25 ms pulse width, 20 V) produced a phasic contraction at the site of stimulation ('direct' response to EFS) which propagated to the other end of the ureter. Section of the ureter at the M-site abolished the propagated response to EFS; after section, EFS applied at the M-site induced a phasic contraction at both the R- and B-sites. Likewise, the application of KCl at the M-site produced phasic contractions at both the R- and B-sites. Tetrodotoxin (1 microM), nifedipine (1 microM) or Bay K 8644 (1 microM) applied at the M-site had no influence on the direct or propagated responses to EFS; nifedipine (10 microM) applied at the M-site abolished the propagated responses without affecting the direct responses to EFS. Bay K 8644 (1 microM) applied at the R-site produced a marked enhancement of the direct response (EFS applied at R-site) while having no effect on the amplitude of the propagated response to EFS.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Propagation of impulses in the guinea-pig ureter and its blockade by calcitonin gene-related peptide (CGRP). 753 4