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Caryl E. Hill - One of the best experts on this subject based on the ideXlab platform.
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non linear relationship between hyperpolarisation and relaxation enables long distance propagation of vasoDilatation
The Journal of Physiology, 2011Co-Authors: Stephanie E Wolfle, Daniel J Chaston, Kenichi Goto, F R Edwards, Shaun L. Sandow, Caryl E. HillAbstract:Non-technical summary Microvascular Dilatations initiated locally in metabolically active tissues spread rapidly upstream, with little attenuation, to larger vessels whose relaxation results in the necessary increases in local blood flow. While this rapidly spreading response occurs due to the propagation of hyperpolarisation through gap junctions, it is not understood why the Dilatation does not attenuate unless a regenerative electrical mechanism is involved. We show in skeletal muscle arterioles in vivo that no such regenerative electrical phenomenon exists. Instead, the local Dilatation spreads without attenuation because the initial hyperpolarisation is supramaximal and the impact of voltage on Dilatation is restricted to a narrow voltage window near the resting membrane potential. Knowledge of this mechanism increases our understanding of the processes which control blood flow to organs and explains how these processes can be compromised in diseases in which endothelial function is reduced. Abstract Blood flow is adjusted to tissue demand through rapidly ascending vasoDilatations resulting from conduction of hyperpolarisation through vascular gap junctions. We investigated how these Dilatations can spread without attenuation if mediated by an electrical signal. Cremaster muscle arterioles were studied in vivo by simultaneously measuring membrane potential and vessel diameter. Focal application of acetylcholine elicited hyperpolarisations which decayed passively with distance from the local site, while Dilatation spread upstream without attenuation. Analysis of simultaneous recordings at the local site revealed that hyperpolarisation and Dilatation were only linearly related over a restricted voltage range to a threshold potential, beyond which Dilatation was maximal. Experimental data could be simulated in a computational model with electrotonic decay of hyperpolarisation but imposition of this threshold. The model was tested by reducing the amplitude of the local hyperpolarisation which led to entry into the linear range closer to the local site and decay of Dilatation. Serial section electron microscopy and light dye treatment confirmed that the spread of Dilatation occurred through the endothelium and that the two cell layers were tightly coupled. Generality of the mechanism was demonstrated by applying the model to the attenuated propagation of Dilatation found in larger arteries. We conclude that long distance spread of locally initiated Dilatations is not due to a regenerative electrical phenomenon, but rather a restricted linear relationship between voltage and vessel tone, which minimises the impact of electrotonic decay of voltage. Disease-related alterations in endothelial coupling or ion channel expression could therefore decrease the ability to adjust blood flow to meet metabolic demand.
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Non-linear relationship between hyperpolarisation and relaxation enables long distance propagation of vasoDilatation.
The Journal of physiology, 2011Co-Authors: Stephanie E Wolfle, Daniel J Chaston, Kenichi Goto, F R Edwards, Shaun L. Sandow, Caryl E. HillAbstract:Blood flow is adjusted to tissue demand through rapidly ascending vasoDilatations resulting from conduction of hyperpolarisation through vascular gap junctions. We investigated how these Dilatations can spread without attenuation if mediated by an electrical signal. Cremaster muscle arterioles were studied in vivo by simultaneously measuring membrane potential and vessel diameter. Focal application of acetylcholine elicited hyperpolarisations which decayed passively with distance from the local site,while Dilatation spread upstream without attenuation. Analysis of simultaneous recordings at the local site revealed that hyperpolarisation and Dilatation were only linearly related over a restricted voltage range to a threshold potential, beyond which Dilatation was maximal. Experimental data could be simulated in a computational model with electrotonic decay of hyperpolarisation but imposition of this threshold. The model was tested by reducing the amplitude of the local hyperpolarisation which led to entry into the linear range closer to the local site and decay of Dilatation. Serial section electron microscopy and light dye treatment confirmed that the spread of Dilatation occurred through the endothelium and that the two cell layers were tightly coupled. Generality of the mechanism was demonstrated by applying the model to the attenuated propagation of Dilatation found in larger arteries.We conclude that long distance spread of locally initiated Dilatations is not due to a regenerative electrical phenomenon, but rather a restricted linear relationship between voltage and vessel tone, which minimises the impact of electrotonic decay of voltage. Disease-related alterations in endothelial coupling or ion channel expression could therefore decrease the ability to adjust blood flow to meet metabolic demand.
M. Brehmer - One of the best experts on this subject based on the ideXlab platform.
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Minimally invasive management of ureteral strictures: a 5-year retrospective study
World Journal of Urology, 2019Co-Authors: C. Reus, M. BrehmerAbstract:Introduction Ureteric strictures are well-documented complications related to surgery or radiation therapy. Minimally invasive treatment using endoscopic Dilatation or laser incision is the standard practice. There are no existing guidelines on which techniques to use in the treatment of different stricture types and a paucity of data regarding long-term results. Purpose Our study aimed to retrospectively assess the long-term efficacy of minimally invasive treatment in benign and malignant ureteric strictures. Materials and methods Over a 5-year period, 2007–2012, we analyzed the data of 59 consecutive patients undergoing minimally invasive treatment for symptomatic ureteric strictures. We excluded 16 patients from final analysis due to failed access or loss to follow-up. All patients but one were treated with antegrade, retrograde balloon or catheter Dilatations. Successful outcome was defined as an asymptomatic, completely catheter free patient, with stable renal function. Results 43 patients were eligible for retrospective final analysis. The largest proportion of strictures occurred following surgery combined with radiotherapy 8/43 (19%). Preoperative decompression was required in 30/43 (70%). We identified 32/43 (75%) balloon Dilatations, 10/43 (23%) catheter Dilatations and 1/43 (2%) laser incision. Overall success rate was 31/43 (72%). All 6 recurrences occurred within 36 months, 4 within the first 12 months. 3/6 patients were successfully re-dilated. Conclusion Minimally invasive treatment is a worthwhile alternative in strictures due to previous radiation and/or surgical treatment of malignancies. Most recurrences occurred within the first year. However, late recurrences arise; therefore, patients should be subject to long-term follow-up. Moreover, re-Dilatation may be required.
Stephanie E Wolfle - One of the best experts on this subject based on the ideXlab platform.
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non linear relationship between hyperpolarisation and relaxation enables long distance propagation of vasoDilatation
The Journal of Physiology, 2011Co-Authors: Stephanie E Wolfle, Daniel J Chaston, Kenichi Goto, F R Edwards, Shaun L. Sandow, Caryl E. HillAbstract:Non-technical summary Microvascular Dilatations initiated locally in metabolically active tissues spread rapidly upstream, with little attenuation, to larger vessels whose relaxation results in the necessary increases in local blood flow. While this rapidly spreading response occurs due to the propagation of hyperpolarisation through gap junctions, it is not understood why the Dilatation does not attenuate unless a regenerative electrical mechanism is involved. We show in skeletal muscle arterioles in vivo that no such regenerative electrical phenomenon exists. Instead, the local Dilatation spreads without attenuation because the initial hyperpolarisation is supramaximal and the impact of voltage on Dilatation is restricted to a narrow voltage window near the resting membrane potential. Knowledge of this mechanism increases our understanding of the processes which control blood flow to organs and explains how these processes can be compromised in diseases in which endothelial function is reduced. Abstract Blood flow is adjusted to tissue demand through rapidly ascending vasoDilatations resulting from conduction of hyperpolarisation through vascular gap junctions. We investigated how these Dilatations can spread without attenuation if mediated by an electrical signal. Cremaster muscle arterioles were studied in vivo by simultaneously measuring membrane potential and vessel diameter. Focal application of acetylcholine elicited hyperpolarisations which decayed passively with distance from the local site, while Dilatation spread upstream without attenuation. Analysis of simultaneous recordings at the local site revealed that hyperpolarisation and Dilatation were only linearly related over a restricted voltage range to a threshold potential, beyond which Dilatation was maximal. Experimental data could be simulated in a computational model with electrotonic decay of hyperpolarisation but imposition of this threshold. The model was tested by reducing the amplitude of the local hyperpolarisation which led to entry into the linear range closer to the local site and decay of Dilatation. Serial section electron microscopy and light dye treatment confirmed that the spread of Dilatation occurred through the endothelium and that the two cell layers were tightly coupled. Generality of the mechanism was demonstrated by applying the model to the attenuated propagation of Dilatation found in larger arteries. We conclude that long distance spread of locally initiated Dilatations is not due to a regenerative electrical phenomenon, but rather a restricted linear relationship between voltage and vessel tone, which minimises the impact of electrotonic decay of voltage. Disease-related alterations in endothelial coupling or ion channel expression could therefore decrease the ability to adjust blood flow to meet metabolic demand.
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Non-linear relationship between hyperpolarisation and relaxation enables long distance propagation of vasoDilatation.
The Journal of physiology, 2011Co-Authors: Stephanie E Wolfle, Daniel J Chaston, Kenichi Goto, F R Edwards, Shaun L. Sandow, Caryl E. HillAbstract:Blood flow is adjusted to tissue demand through rapidly ascending vasoDilatations resulting from conduction of hyperpolarisation through vascular gap junctions. We investigated how these Dilatations can spread without attenuation if mediated by an electrical signal. Cremaster muscle arterioles were studied in vivo by simultaneously measuring membrane potential and vessel diameter. Focal application of acetylcholine elicited hyperpolarisations which decayed passively with distance from the local site,while Dilatation spread upstream without attenuation. Analysis of simultaneous recordings at the local site revealed that hyperpolarisation and Dilatation were only linearly related over a restricted voltage range to a threshold potential, beyond which Dilatation was maximal. Experimental data could be simulated in a computational model with electrotonic decay of hyperpolarisation but imposition of this threshold. The model was tested by reducing the amplitude of the local hyperpolarisation which led to entry into the linear range closer to the local site and decay of Dilatation. Serial section electron microscopy and light dye treatment confirmed that the spread of Dilatation occurred through the endothelium and that the two cell layers were tightly coupled. Generality of the mechanism was demonstrated by applying the model to the attenuated propagation of Dilatation found in larger arteries.We conclude that long distance spread of locally initiated Dilatations is not due to a regenerative electrical phenomenon, but rather a restricted linear relationship between voltage and vessel tone, which minimises the impact of electrotonic decay of voltage. Disease-related alterations in endothelial coupling or ion channel expression could therefore decrease the ability to adjust blood flow to meet metabolic demand.
C. Reus - One of the best experts on this subject based on the ideXlab platform.
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Minimally invasive management of ureteral strictures: a 5-year retrospective study
World Journal of Urology, 2019Co-Authors: C. Reus, M. BrehmerAbstract:Introduction Ureteric strictures are well-documented complications related to surgery or radiation therapy. Minimally invasive treatment using endoscopic Dilatation or laser incision is the standard practice. There are no existing guidelines on which techniques to use in the treatment of different stricture types and a paucity of data regarding long-term results. Purpose Our study aimed to retrospectively assess the long-term efficacy of minimally invasive treatment in benign and malignant ureteric strictures. Materials and methods Over a 5-year period, 2007–2012, we analyzed the data of 59 consecutive patients undergoing minimally invasive treatment for symptomatic ureteric strictures. We excluded 16 patients from final analysis due to failed access or loss to follow-up. All patients but one were treated with antegrade, retrograde balloon or catheter Dilatations. Successful outcome was defined as an asymptomatic, completely catheter free patient, with stable renal function. Results 43 patients were eligible for retrospective final analysis. The largest proportion of strictures occurred following surgery combined with radiotherapy 8/43 (19%). Preoperative decompression was required in 30/43 (70%). We identified 32/43 (75%) balloon Dilatations, 10/43 (23%) catheter Dilatations and 1/43 (2%) laser incision. Overall success rate was 31/43 (72%). All 6 recurrences occurred within 36 months, 4 within the first 12 months. 3/6 patients were successfully re-dilated. Conclusion Minimally invasive treatment is a worthwhile alternative in strictures due to previous radiation and/or surgical treatment of malignancies. Most recurrences occurred within the first year. However, late recurrences arise; therefore, patients should be subject to long-term follow-up. Moreover, re-Dilatation may be required.
Tetsuya Yasunaka - One of the best experts on this subject based on the ideXlab platform.
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diagnostic usefulness of precise examinations with intraductal ultrasonography peroral cholangioscopy and laparoscopy of immunoglobulin g4 related sclerosing cholangitis
Digestive Endoscopy, 2012Co-Authors: Shigeru Horiguchi, Ichiro Sakakihara, Hiroaki Hagihara, Koichiro Tsutsumi, Hironari Kato, Yasuhiro Noma, Hidenori Shiraha, Fusao Ikeda, Naoki Yamamoto, Tetsuya YasunakaAbstract:Herein, a case of immunoglobulin G4 (IgG4)-related sclerosing cholangitis is reported. IgG4 was diagnosed based on observations from peroral cholangioscopy and laparoscopy, and these methods are proposed for definitive and precise diagnosis of this disease. A 76-year-old male patient with inguinal Paget's disease had intrahepatic bile duct Dilatations detected with computed tomography at his periodic check-up. Magnetic resonance cholangiography showed stenosis of the upper common bile duct and poststenotic Dilatation of left intrahepatic bile ducts. The portal tract and bilateral intrahepatic bile ducts were surrounded by a low-density area, facing a tumor-like lesion at segment 2. Cytological examinations of the stenotic and dilated lesions revealed no cellular atypia. Histological examination of the tumor showed normal liver tissue with infiltration of lymphocytes, indicating an inflammatory pseudotumor. Peroral cholangioscopy excluded the possibility of biliary cancer and indicated that the stenotic legion was of submucosal, not mucosal, origin. Laparoscopic observations showed discoloration with wide yellowish-white lobular markings and wide depressed lesions at segments 2 and 7. Liver histology showed mild cholangitis with infiltration of IgG4-positive plasma cells around the bile ducts. Serum IgG4 levels were elevated. From these findings, the patient was diagnosed with IgG4-related sclerosing cholangitis. After treatment with prednisolone, blood liver enzymes and IgG4 rapidly normalized, bile duct Dilatations improved, and the hepatic pseudotumor disappeared. The cholangitis did not recur. In this case, biliary cancer was ruled out by observation with peroral cholangioscopy, and the spread of cholangitis in the liver periphery was verified with laparoscopy; this information could not be obtained with other modalities.
