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

These experiments were designed to study the role of calcium in the modulation of renin secretion by alpha and beta adrenoceptors. Rabbit kidneys were isolated and single-pass perfused with a modified Ringer's solution. Renal perfusion pressure was precisely controlled by an electronic servocontrol system. Tubular events were minimized by ligation of the ureter before initiating the studies. Under these conditions the predominant factor modifying renin secretion was assumed to originate directly on the juxtaglomerular cells. Isoproterenol infused at 0.1, 0.5, 1.0 and 5.0 nM/min/g of kidney weight increased renin secretion in a dose-dependent manner whereas phenylephrine infused at identical molar doses did not. In addition, phenylephrine (5.0 nM/min/g of kidney weight) blocked the usual response to isoproterenol. Removal of calcium from the perfusing medium had no effect on either the response to isoproterenol or the lack of a response to phenylephrine. On the other hand, when calcium is removed from the perfusate or when D-600, a calcium channel blocker, is added to calcium-containing medium, phenylephrine failed to block the usual response to isoproterenol. We conclude that the suppression of beta adrenoceptor stimulation of renin release by alpha adrenoceptor agonists is calcium dependent by a final mechanism as yet undefined, but probably involving movement of calcium into the juxtaglomerular cells.
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PMID:Role of calcium in the interaction of alpha and beta adrenoceptor-mediated renin release in isolated, constant pressure perfused rabbit kidneys. 631 14

Previous studies on the mode of action of flavoxate have shown that the drug exerts a selective and direct muscle relaxant activity. In order to study the mode of action of flavoxate, the following activities were investigated: calcium blocking, inhibition of cyclic AMP phosphodiesterase (PDE), local anaesthetic activity, the effects on the synthesis and release of prostaglandins. In the K+-depolarized guinea-pig taenia coli, contracted by CaCl2, flavoxate and papaverine showed a moderate calcium antagonistic activity. Anticholinergic drugs, such as atropine and emepronium, did not exert a similar action. The antispasmodic activity of a drug can be correlated with inhibition of cyclic AMP phosphodiesterase, and since papaverine is a potent PDE inhibitor, we tested flavoxate for this activity. Flavoxate exerted a PDE inhibitory activity about three and five times greater than that of aminophylline in tissues homogenates of guinea-pig ureter and urinary bladder, respectively. It also showed the same local anaesthetic activity of lidocaine. Finally, the synthesis and release of prostaglandins by urinary bladder muscle in vitro have been investigated before and after treatment with flavoxate. Myolytic activity of papaverine and flavoxate do not involve inhibition of prostaglandins synthesis in rat urinary bladder in vitro. Therefore, the mode of action of flavoxate can be related to a superimposition of myotropic, calcium antagonistic and local anaesthetic activity.
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PMID:Pharmacological studies on the mode of action of flavoxate. 632 16

Renal tubular function has been studied in pig fetuses of 105-112 d gestational age in new-born pigs 5-9 d old. The experiments were performed on anaesthetized animals, urines being collected by inserting a catheter into one ureter of the animal under study. The glomerular filtration rate was estimated and plasma concentrations and urinary excretion of the following substances were measured: sodium, potassium, calcium, ammonia, urea, phosphate, glucose fructose, creatinine, protein and exogenous 4-aminohippuric acid, and inulin. The reabsorption of water was considered in relation to the plasma vasopressin values. New-born pigs were loaded with glucose and fructose in order to determine the maximal tubular transport rate of these substances. Significant changes at birth occur in only a few functions of the tubulus system. Following delivery, major changes are: (1) the increased reabsorption of sodium and water which is probably the most important adaptation to extra-uterine life; (2) an apparent increasing impermeability of the tubular epithelium for creatinine, and (3) the direction of transport of fructose, which is reabsorbed by fetuses whereas neonates demonstrate a net secretion. Glucose and fructose are transported by different mechanisms. The experiments with fructose-loaded piglets demonstrate that there are at least two transport mechanisms for fructose: reabsorption - either passive or active - and secretion. The factors causing a shifting from one mechanism to the other are not yet known.
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PMID:Perinatal development of tubular function in the pig. 651 94

A series of experiments have been carried out in-vitro in order to assess the possibility of using a collagen membrane in the repair of various sections of the urinary tract following operative surgery such as the removal of a stone from the ureter. The collagen film has been tested for its compatability with urine, its ability to prevent leakage of fluid in a simulated wound in-vitro and for its ability to withstand any degradative effect of liver and kidney homogenates. The material was not significantly degraded by either urine or by tissue homogenates and was able to prevent leakage of fluid under the experimental conditions employed. Although some slight build-up of calcium and some trace elements took place after incubation in urine over a six-day period this was not significant. On the basis of the results obtained it has been decided to proceed to in-vivo trials on rabbits using the collagen membrane. The possibility of using such a material in partial nephrectomy operations is discussed.
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PMID:Preliminary development of a collagen membrane for use in urological surgery. 652 51

Recent experiments have shown that 1,25-dihydroxyvitamin D3-like material is produced in cultured nonrenal cells and may be present in the sera of anephric patients. We reexamined the question of whether 1,25-dihydroxyvitamin D3 can be synthesized extrarenally in the rat in vivo. To intact, sham-operated, ureter-ligated, or acutely nephrectomized vitamin D-deficient rats raised on a diet normal in calcium and phosphorus, we gave a physiologic dose of high-specific-activity 25-hydroxy-[3H]vitamin D3 (3.6-3.8 microCi; approximately equal to 25 pmol per rat). Twenty-four hours later we examined their tissues and plasma for the presence of radiolabeled 1,25-dihydroxyvitamin D3. Large amounts of radioactivity that behaved chromatographically as identical with authentic 1,25-dihydroxyvitamin D3 were present in the plasma, bone, and intestine of the intact, sham-operated, or ureter-ligated rats. However, no radioactivity eluting in a manner similar to 1,25-dihydroxyvitamin D3 was found in plasma, bone, or intestine of acutely nephrectomized rats. We conclude that, in the acutely nephrectomized living rat, 1,25-dihydroxyvitamin D3 is not present in plasma, bone, or intestine in quantities detectable by the sensitive techniques we have used. No conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 was observed during a 24-hr period after nephrectomy of vitamin D-deprived rats. This fact casts doubt upon the significance of the in vitro production of 1,25-dihydroxyvitamin D3 by nonrenal cells as an in vivo phenomenon.
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PMID:Do tissues other than the kidney produce 1,25-dihydroxyvitamin D3 in vivo? A reexamination. 657 38

Chlorpromazine (ClP) and trifluoperazine (TFP) depress electrical and mechanical activity of ureter smooth muscle cells. Contraction was depressed by less doses of the substances applied as compared with the processes responsible for generation of spike activity. ClP causes the displacement of the dose-effect curve for Ca2+ towards larger concentrations of the latter. Trifluoperazine displaces the dose-effect curve for contraction to the right and downwards. It is concluded that inhibition of contraction and depression of ClP and TFP spikes is due to the calmodulin blocking on which kinase activity of myosin light chains depends. It is supposed that processes responsible for activation of the membrane systems of Ca2+ transport in the process of spike generation are also calmodulin-dependent.
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PMID:[Study of electromechanical coupling in smooth muscle cells of the ureter using phenothiazines]. 672 4

The action potential of human ureter was recorded in vitro by sucrose gap technique and the effects of some cations and drugs were studied. The action potential was composed of an initial fast component of spike and a subsequent slow component, a plateau, without a definite after-positive potential. Duration of the action potential was 1.0 +/- 0.1 (mean +/- standard deviation, n = 5) seconds at resting membrane potential level and 0.8 +/- 0.1 seconds at 90 per cent of the repolarization level. Ratio of plateau potential to spike potential was 80 +/- 4 per cent. The results of ionic influence suggested that calcium played an important role in the generation of spike potential and sodium in the generation of plateau potential. The application of noradrenaline and serotonin showed an excitatory effect which was observed as an increase of spontaneous discharge with depolarization of membrane potential and slow depolarization preceding the action potential. The slow depolarization was never observed in control preparations. These findings suggested that the ureter might have the capacity to generate a pacemaker-like slow depolarization which could conceivably relate to the automaticity of the ureter. Acetylcholine showed an excitatory effect only when the preparation was pretreated by physostigmine.
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PMID:Action potential of isolated human ureter recorded with sucrose gap technique. 683 25

Phenthiazamine was developed by Sekizawa et al. as a centrally acting anesthetic for fish. Frog sympathetic ganglion was used as a model to elucidate the mechanism of its anesthetic action. The positive ganglionic potential was enhanced immediately after application; then, the potential and the late negative ganglionic potential were markedly reduced by an anesthetic concentration of this compound. The hyperpolarization caused by 1 mM dopamine was enhanced by phenthiazamine. This enhancement of dopamine hyperpolarization and of the positive ganglionic potential may coincide with the fact that cyclic adenosine monophosphoric acid (cAMP) phosphodiesterase was inhibited by the compound as shown in our previous paper. Guinea-pig ileum contraction elicited by electrical field stimulation and by dimethyl-phenyl-piperadinium (DMPP) was reduced by a similar concentration of this compound, while the contraction elicited by acetylcholine and methacholine was not inhibited. The inhibition of contraction elicited by electrical field stimulation and DMPP may thus due to inhibition of acetylcholine release by this compound. The inhibition of ileum contraction by this compound was reversed by higher doses of Ca2+ (5.5 mM). The time required to reduce the positive ganglionic potential in the sympathetic ganglion by phenthiazamine was prolonged in the presence of higher concentrations of Ca2+. The Ca2+-dependent action potential of guinea-pig ureter was reduced by this compound, whereas it did not affect the Na+-dependent action potential.
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PMID:Pharmacological analysis of the mechanism of action of phenthiazamine, a piscine anesthetic. 697 Aug 7

Experiments were carried out on smooth muscle cells (SMC) of the guinea-pig ureter by the double sucrose gap method with simultaneous recording of electrical and contractile activities. The effect of histamine on SMC was studied in normal Krebs solution and in sodium-free Krebs solution with TEA. In normal Krebs solution, histamine was shown to increase the duration of AP plateau and contraction. In sodium-free Krebs solution with TEA, the APs of ureter SMC also had a plateau that was determined by the increased calcium conduction of the membrane. In these conditions, histamine provoked a decrease in the duration of the AP plateau and contraction. The histamine effect was blocked by phencarol both in normal and sodium-free Krebs solution with TEA. A possible role of sodium, calcium and potassium ions in the modulating action of histamine on excitation of ureter SMC is discussed.
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PMID:[Mechanism of modulating effect of histamine on the excitation and contraction of smooth muscles of the ureter]. 717 28

Sixty-eight children (ages ranging from 5 months to 16 years) with urolithiasis were treated between 1966 and 1979. There were 36 females (53%) and 32 males (47%). Sixteen children (24%) had associated urinary tract infection; 4 out of these (6%) presented with urinary tract malformation. Fifty-five calculi (89%) were found in the upper urinary tract (kidney and ureter); 24 of the chemically studied calculi (80%) were made of calcium salts. In 30 children, metabolic investigations were carried out, leading to the discovery of hypercalciuria in 17 (57%). In one patient, important vesico-ureteral reflux associated with urolithiasis led to renal failure.
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PMID:[Urolithiasis in Isreali children (author's transl)]. 723 27


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