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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

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

1. Sodium-calcium exchange was studied in single enzymatically isolated cells of the guinea-pig ureter using the Ca2(+)-sensitive fluorescent dye Indo-1 to monitor the intracellular Ca2+ concentration ([Ca2+]i). Patch pipettes containing Indo-1 were used to introduce the dye into cells, to set the intracellular Na+ concentration ([Na+]i) and control the membrane potential during experiments. 2. With [Na+]i set at 11-12 mM and a membrane potential of -60 or -70 mV, brief depolarization of ureter cells elicited typical voltage-gated inward currents associated with rapid increases in [Ca2+]i which showed a bell-shaped potential dependence. If Ca2+ currents were blocked with nifedipine, depolarization led to slower rises in [Ca2+]i. The rates and amplitudes of these increased monotonically with progressively larger depolarizations up to +120 mV. 3. The nifedipine-resistant rises in [Ca2+]i elicited by depolarization were potentiated when the extracellular sodium concentration ([Na+]o) was reduced. Basal levels of [Ca2+]i also increased as [Na+]o was reduced, although the dependence of this effect on [Na+]o was smaller than would be predicted if [Ca2+]i was set only by a Na(+)-Ca2+ exchange process. 4. The nifedipine-insensitive rises in [Ca2+]i elicited by depolarization were potentiated at higher basal levels of [Ca2+]i. 5. The ability of cells to reduce [Ca2+]i rapidly following Ca2+ loading during voltage-gated transients was markedly inhibited if the Na+ concentration gradient was reversed, but was little affected if the Na+ gradient was decreased by 25 or 50%. Recovery from a Ca2+ load caused by reversal of the Na+ gradient could be induced by removal of Cao2+ in the continuing absence of Nao+, indicating the importance of a Na(+)-independent [Ca2+]i-lowering system. 6. The results demonstrate that Na(+)-Ca2+ exchange can modulate [Ca2+]i when [Na+]i and the membrane potential are set at or near their physiological levels in these smooth muscle cells. [Ca2+]i does not, however, appear to be markedly sensitive to the Na+ concentration gradient under the conditions employed for these experiments, suggesting that a Na(+)-independent Ca2+ extrusion system is mainly responsible for regulating [Ca2+]i under normal conditions.
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PMID:Alterations in [Ca2+]i mediated by sodium-calcium exchange in smooth muscle cells isolated from the guinea-pig ureter. 260 45

The modifying effects of 17 environmental chemicals on the development of lesions in the urinary bladder of rats with unilateral ureteric ligation were investigated. Lesions were initiated by treatment of the animals with 0.05% N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) for 2 weeks, and then test chemicals were given for 22 weeks. The lesions of the urinary bladder found were preneoplastic papillary or nodular hyperplasias (PN hyperplasias) and papillomas. Additions of sodium saccharin (5%), sodium o-phenylphenate (2%), butylated hydroxyanisole (2%), and sodium L-ascorbate (5%) to the diet had significant promoting effects on the incidences and numbers of PN hyperplasias and papillomas per 10 cm of basement membrane of the urinary bladder in this system. Sodium erythorbate (5%), ethoxyquin (0.8%) and carbazole (0.6%) significantly increased the incidence of PN hyperplasias. N-Nitrosopyrrolidine (0.02%) did not affect the incidence or number of PN hyperplasias but increased those of papillomas. Sodium o-phenylphenate also induced PN hyperplasias in rats without BBN-initiation. Ascorbic acid, ascorbic stearate, three dihydroxyphenols, methylhydroquinone, pyrogallol, quinoline, and uric acid did not show promoting activity in this test system. Thus, 8 of 17 chemicals tested had various promoting effects on urinary bladder carcinogenesis. These results show that this test system of BBN-initiated, unilaterally ureter-ligated rats should be useful for the detection of new bladder carcinogens and promoters.
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PMID:Short-term screening of promoters of bladder carcinogenesis in N-butyl-N-(4-hydroxybutyl)nitrosamine-initiated, unilaterally ureter-ligated rats. 393 81

1. The capacity of adaptation of toads (Bufo bufo) to environments of high salinity was studied and the relative importance of skin, kidney and urinary bladder in controlling the balance of water and salt was assessed.2. Toads were kept in NaCl solutions of 20, 50, 110, 150 and 220 mM and studied in their fourth week of adaptation. A group of animals considered as ;control' was kept in wet soil with free access to water. Plasma, ureter urine, and bladder and colon contents were analysed for sodium, potassium, chloride and osmolality, and total body sodium and water were determined. Absorption of water and (22)Na through the skin, and water flow and sodium excretion through the ureter, of intact animals was studied. Hydrosmotic water transport through the isolated urinary bladder of ;control' and adapted animals was determined. The effects of pitressin and aldosterone on the water and sodium balance are described.3. The survival rates of toads kept in saline concentrations up to 150 mM were identical to that of ;control' animals, but half of the animals kept in 220 mM died within 4 weeks.4. There is a linear correlation between the sodium concentrations and osmolality of plasma and of the external media.5. The sodium concentration in colon contents rose with rising external concentrations, up to values higher than the values in plasma.6. Sodium concentrations and osmolalities of ureter and bladder urine increased in adapted animals, the values for bladder urine becoming much higher than those for ureter urine in animals adapted to 110, 150 and 220 mM.7. Total body water, as a percentage of total weight was kept within very narrow limits, although the total body sodium increased with adaptation.8. Absorption of water through the skin for the same osmotic gradients was smaller in adapted than in ;control' animals.9. The ureteral output of water of toads adapted to 110 and 150 mM-NaCl was larger than the water absorption through the skin.10. Skin absorption of sodium was lower in animals adapted to concentrated saline solutions than in ;control' animals.11. Sodium output by the ureter was identical to skin absorption in ;control' animals adapted to 20, 50 and 110 mM-NaCl but was higher in animals adapted to 150 mM-NaCl.12. Aldosterone increased the absorption of sodium in ;control' and adapted toads, but at all dose levels absorption by control was greater than by adapted animals.13. The stimulation of water absorption by vasopressin in vivo or in isolated bladders was not modified in animals adapted to high salinities.
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PMID:Salt adaptation in Bufo bufo. 463 11

The secretion and synthesis of renin were studied in mice by measuring aortic, right and left renal vein renin, renal renin, and mRNA for renin. The role of the macula densa was evaluated in a kidney made hydronephrotic by tying the ureter 6 weeks earlier. There was no net secretion of renin from the left hydronephrotic kidney even when the mice were placed in a high secretory state by sodium restriction or enalapril. Sodium restriction and enalapril increased renin content to a similar extent in the normal and hydronephrotic kidney. High sodium intake decreased renin content in the normal and hydronephrotic kidney and also decreased the enalapril-stimulated renin content. Changes in mRNA in the same direction to renal renin implied that this was due to increased synthesis. Thus secretion and synthesis of renin can be disassociated. The macula densa is important for renin secretion but not for the stimulation of synthesis.
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PMID:Role of the macula densa in renin synthesis and secretion. 806 May 79

Unfortunately, the nonoperative treatment of hydronephrosis, in wide use today, cannot be evaluated until after many decades. Long-term animal experiments offer a peekhole into the future. Partial obstruction of the left ureter was created in newborn rats. Its effects were studied after 1 year. In order to stress the system, the investigations were performed under hydropenic conditions. On the obstructed side, the renal pelvis was considerably enlarged; however, the microstructure of the kidney was only slightly affected. Renal blood flow was decreased (-17%) due to a rise in vascular resistance. Filtration was less affected (-9%), probably as a result of increased filtration fraction. Water excretion, including that of free water, was increased (+59%) due to a decreased reabsorption. Potassium excretion was decreased (-59%) either due to increased reabsorption and/or decreased secretion. Sodium excretion followed a similar pattern (-24%) although without statistical significance. The contralateral side compensated for the ipsilateral decreases in blood flow and filtration. Ipsilateral tubular functions were not compensated for, which indicates an acute situation that is reaffirmed by the finding of a normal hematocrit and serum osmolality/electrolytes. The changes in tubular functions were thus considered to be due to the hydropenic stress, but inescapably an incompetent concentration capacity exists. The changes in the obstructed kidney were thus moderate, some of which were fully compensated for, but, most important, all were nonprogressive. The study supports the nonoperative treatment of these patients, provided that the follow-up guarantees catch-up of the exceptional cases that deteriorate, especially during infancy.
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PMID:Experimental partial ureteric obstruction in newborn rats. IX. Renal morphology and function after 1 year of obstruction. 931 18