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

The role of sodium in calcium active transport from the ureter muscle, preliminarily enriched in these ions, was studied in large ouabain concentration (10(-4) mmol/l) for complete inhibition of the Na(+)-K(+)-pump. The determination of intracellular concentrations of sodium and calcium ions (by flame photometry and isotopic analysis, resp.) showed that a fast decrease of intracellular calcium content was accompanied by an increase of intracellular sodium. With high sodium ions concentration in medium (above 100 mmol/l), the velocity of the decrease in intracellular calcium content reached the maximal value, the efflux of additional enriched calcium ions occurring within 10-15 min. The decrease of intracellular calcium content was in sigmoidal dependence on the concentration of sodium ions in the medium. The electrogenic Na(+)-Ca(++)-exchange system seems to play a major role in calcium-enriched muscles for the decrease of intracellular calcium content.
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PMID:[The role of the sodium gradient in the efflux of Ca++ ions from the smooth muscle cells of the ureter]. 166 63

Diclofenac sodium, one of the prostaglandin synthesis inhibitors was evaluated in terms of passage or movement of ureteric stones upto the size of 0.5 cm in a series of 80 patients. Forty-six (57.5%) patients passed the stone within a period of 4 weeks. This frequency of stone passage was significantly higher when compared with stone passage of similar size in other series (P less than 0.001). In 17 (56.6%) out of 30 patients, stone moved from upper and middle ureter to the lower ureter which is also significant from therapeutic point of view. Complete pain relief was achieved in 67 (84%) patients. No side effects of the drug noted in this series. The sequence of events following ureteral obstruction by the stone, based on recent experimental and clinical studies is discussed and possible mechanism of action of diclofenac sodium was highlighted.
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PMID:Role of prostaglandin synthesis inhibitors in the passage of ureteric calculus. 176 67

The role of the electrogenic Na(+)-Ca(2+)-exchange mechanism in regulating the spike activity of the ureter was studied. The ureter cells were shown to be capable of generating action potentials (AP) in sodium-free Krebs solution. The time during which the spikes are generated is in exponential dependence on the concentration of calcium ions in the medium, [Ca2+]o within 2.5 to 15 mmol/l. Simultaneously with the generation of the spikes, accumulation of calcium in the muscles is observed, proportional to the increase of [Ca2+]o. The addition of as little as 20 mmol/l Na+ or Li+ ions into the solution restores the prolonged electrical activity of the ureter. Under these conditions, the decrease of intracellular Ca2+ within 5 min was more than two times larger as compared with that in sodium-free medium. Upon substituting Ba2+ ions for Ca2+ ions in Krebs solution AP are generated within an interval which was the longer the higher the Ba2+ concentration in the medium. Li+ ions can replace Na+ ions in maintaining AP and in extruding calcium from the cell. It is supposed that the generation of the stable spike activity of the ureter depends on the functioning of Na(+)-Ca(2+)-exchange mechanism.
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PMID:Factors controlling the intracellular concentration of calcium and the spontaneous activity of the ureter. 186 94

Previous studies have indicated that the effects of renal alpha-2 adrenoceptor stimulation are mediated through the blockade of the renal effects of vasopressin. If this premise is correct then 1) specific antagonists of the antidiuretic effect of vasopressin (V2 antagonists) should mimic alpha-2 adrenoceptor stimulation and 2) in the presence of V2 antagonists, the diuretic and natriuretic effect of clonidine should be attenuated. The renal effects of [d(CH2)5,D-Ile2,Ile4]AVP, a specific V2 antagonist, were studied. On the day of the experiment, uninephrectomized rats were anesthetized, and the carotid artery and jugular vein were cannulated for recording blood pressure and saline infusion, respectively. The left kidney was exposed and the ureter cannulated. A 31-gauge needle was advanced into the renal artery to permit direct i.r. infusion of study drugs. Bolus doses of the V2 antagonist (0, 1, 3, 10, or 30 nmol/kg i.v.) produced a dose-related increase in urine volume and free water clearance at all doses tested. Sodium excretion increased only at the higher doses (10 and 30 nmol/kg). This dose-related dissociation in water and then sodium excretion is similar to that observed after i.r. clonidine infusions. In the presence of the V2 antagonist, clonidine (3 micrograms/kg/min) had no effect on urine volume or free water clearance but significantly decreased the excretion of sodium from control. These results demonstrate that V2 antagonists mimic the effects of i.r. clonidine. As well, in the absence of vasopressin (V2 antagonism), the effects of clonidine are attenuated. Moreover, they are also consistent with not only an antidiuretic role for endogenous vasopressin but also an antinatriuretic one.
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PMID:Role of vasopressin in response to intrarenal infusions of alpha-2 adrenoceptor agonists. 197 99

In vivo 23Na magnetic resonance images of guinea pig kidney were obtained at 2.1 T using a spin-echo sequence with an echo time of 19 ms. The intact kidney showed a very strong signal intensity in the sodium image. The signal intensity of the kidney decreased to 55% after ligation of the renal artery together with the vein and the ureter. The total sodium content in the excised kidney after arterial occlusion, measured by flame photometry, was 24% higher than that in the intact kidney. The transverse relaxation time (T2) of the extracellular sodium in the isolated kidney decreased to one-third of that in the intact kidney. This shortening of T2 may be partly responsible for the decrease in the 23Na signal intensity from the kidney after arterial occlusion.
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PMID:Sodium-23 MR imaging of the kidney in guinea pig at 2.1 T, following arterial, venous, and ureteral ligation. 207 27

The effects of stimulation of renal mechano- and chemoreceptors on the afferent renal nerve activity (ARNA) were observed in 44 anesthetized rabbits. The results obtained were as follows: (1) Elevation of ureteral pressure (UP) could induce an increase in integral value of ARNA by 175.13 +/- 22.41% (P less than 0.001). (2) KCl (0.15 mol/L) and NaCl (1 mol/L) perfused retrogradely into pelvis via ureter route resulted in increase of integral value of ARNA by 253.79 +/- 21.64% and 172.17 +/- 15.19% (P less than 0.001), respectively. (3) Four patterns of afferent unit discharge were found: no spontaneous activity, regular spontaneous activity, regular spontaneous activity with burst and irregular spontaneous activity. (4) The units of afferent renal nerve with no spontaneous activity were activated markedly by elevation of UP, while the units with spontaneous activity showed no change. (5) In response to the retrograde perfusion of KCl (0.15 mol/L) and NaCl (1 mol/L) into pelvis, the activity in units with spontaneous discharge increased markedly by 210.70 +/- 23.40% and 140.07 +/- 15.72% (P less than 0.001), respectively, and the other units may be recruited concomitantly. (6) The units with no spontaneous discharge were activated by renal artery occlusion. The results implied that there are mechanoreceptor, R1 and R2 chemoreceptors in the kidney of the rabbit, and they may sense the change in UP, renal ischemia and ionic (K+, Na+) concentration of the solute within pelvis.
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PMID:[Observation on the afferent nerve activity induced by stimulation of renal receptors in the rabbits]. 208 72

In presence of the specific Na(+)-K(+)-pump blocking agent ouabain reestablishment of spike activity of the ureter smooth muscle cells occurred, the latters having been preliminarily incubated in sodium-free solution. The reestablishment lasted not over 15 minutes. After substitution of calcium ions with barium ones, the period of the spike generation increased. The lithium ions are able to substitute the sodium ions for reestablishing the calcium action potentials. The ureter activity seems to be reestablished in sodium-free solution with participation of the Na+/Ca(++)-exchange mechanism, which is quite specific for the calcium ions.
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PMID:[The regulation of the spontaneous activity of the ureter by a Na+/Ca++-metabolic mechanism]. 215

Intracellular concentration of Ca++ ions was determined by the isotope analysis method for the guinea-pig ureter smooth muscle cells in solutions containing Ca++, Na+ and Li+. It was shown that the Ca++ concentration in muscles incubated in Na(+)-free solution containing 2.5 to 15 mmol/l Ca++, reached the maximal value during the period in which spikes were recorded. In the muscles enriched by calcium, intracellular Ca++ concentration was reduced by over 2.5 times in solutions containing Na+ and Ca++ ions (120 mmol/l and 10 mmol/l, resp.,) as compared with Na(+)-free medium. The reducing of calcium content was mainly obvious during first 5 min. Na+ ions were not specific for calcium removal from cells, Li+ ions being able to substitute them in this process. The findings suggest a possible participation of Na(+)-Ca(++)-exchange mechanism in the maintenance of the calcium homeostasis in the ureter smooth muscle cells.
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PMID:[The role of cations from the external medium in regulating the intracellular Ca++ ion concentration in ureteral smooth muscle cells]. 217 5

A method is proposed for analysing kinetic curves of the smooth muscle contraction--relaxation approved on smooth muscle preparations of ureter and taenia coli. A notion of the velocity coefficient is introduced. It is the parameter which gives a quantitative characteristics of changes in the dynamics of muscle contraction and relaxation under the effect of factors modifying the contractile response. In order to illustrate the application of this parameter studies were carried out of the effect of sodium-free medium, monensin, and of temperature decrease on the contractile activity of the smooth muscle tissue of the ureter. The method can be useful while investigating the regularities of electro- and pharmacomechanical conjunction in the smooth muscles, as well as during pharmacological screening of compounds--regulators of calcium homeostasis in myocytes and their contractile activity.
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PMID:[Kinetic analysis of contraction-relaxation process in smooth muscles]. 236 8

1. The intracellular Na+ activity (aNai) of the smooth muscle cells from guinea-pig ureter has been measured using double-barrelled Na+-sensitive micro-electrodes. aiNa in modified Krebs solution at 35 degrees C was of a mean 7.4 +/- 2.9 mM (n = 32, S.D. of an observation), equivalent to a Na+ equilibrium potential (ENa) of +66.7 mV. Membrane potential (Em) was of a mean -50.8 +/- 4.6 mV. 2. Inhibition of the Na+ pump by application of ouabain or removal of external K+ (K+o) resulted in a restricted rise of aNai. The rate of rise was faster in the presence of ouabain (10(-4) M) but the stabilized aNai was not significantly different from that observed after the prolonged absence of K+o. The mean aiNa recorded after prolonged Na+ pump inhibition was 20.6 +/- 5.5 mM (n = 28), equivalent to an ENa of +39.6 mV. Neither removal of K+o after aNai had stabilized in the presence of ouabain nor application of ouabain after aNai had stabilized in K+-free solution caused a rise in aiNa, suggesting that the Na+ pump was fully inhibited by either procedure. 3. Reduction of Na+o resulted in a rapid fall in aiNa against the electrochemical gradient, both before and after Na+ pump inhibition. At each level of Na+o, aNai stabilized such that ENa remained approximately constant in either condition. Readdition of Na+o resulted in a rapid recovery of aNai. 4. Elevation of Ca2+o (at constant Na+o) caused a fall in aNai of much the same time course as that observed on reduction of Na+o, both before and after Na+ pump inhibition. The extent of the fall was dependent upon the initial aNai. Reduction of Ca2+o resulted in a rise in aNai. 5. Elevation of the external divalent cation concentration with Mn2+ or, to a lesser extent, Mg2+ reduced aiNa in the presence of a functional Na+ pump. But after prolonged exposure to ouabain or K+-free solution, elevation of Mg2+o had no effect on aiNa while application of Mn2+o caused a slow rise. These results suggest that Ca2+o affects aiNa in two ways. One is mimicked by Mg2+ and Mn2+ and is probably due to alteration of the Na+ leak. The other is a specific effect, revealed by Na+ pump inhibition. 6. It is concluded that aiNa can be maintained far from equilibrium in the absence of a functional Na+ pump. Several lines of evidence are discussed which indicate the participation of Na+-Ca2+ exchange in Na+ extrusion in this condition.
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PMID:Investigation of factors affecting the intracellular sodium activity in the smooth muscle of guinea-pig ureter. 244 70


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