Browsing by Author "Heuser, M."

Introduction: Peritubular renal microcirculation has not been directly visualized in acute ureteral obstruction. Therefore, we used epiilluminescence intravital microscopy and an animal model for the assessment of microvascular perfusion. Materials and methods: In group 1 (n = 5) the left kidney of Wistar rats was exteriorized and placed on a heatable stage for microcirculatory analysis. FITC-dextran was injected for plasma staining. Microcirculatory stability of the model was assessed by a repeated intravital microscopy at baseline, 60, and 120 minutes. In detail, the functional peritubular vessel density (FVD, total vessel length per area in cm/cm(2)), the red blood cell velocities and diameters in/of arterioles and peritubular capillaries and the perfusion index were measured. In group 2 (n = 7) the left ureter was obstructed after baseline microscopy. In a third group (n = 6) the influence of the antidiuretic and vasoconstrictive peptide gastrin releasing peptide on peritubular microcirculation of the obstructed kidney was measured. Results: Repeated intravital microscopy did not induce major microcirculatory disturbances in group 1. Acute ureteral obstruction significantly decreased the index of peritubular perfusion. Moreover, FVD was found decreased at 120 minutes after a small rise at 60 minutes. Whereas blood cell velocities were not changed, arteriolar diameters were decreased after 120 minutes. GRP infusion lowered intrapelvic pressures at 60 and at 120 minutes. The transient increase of FVD (group 2) was not observed. The calculated peritubular flow remained nearly constant compared to a decrease in group 2. Histological assessment did not reveal any microscopy induced renal damage nor any differences between the groups. Conclusions: (1) The model is stable for a time period of at least 120 minutes and allows for the direct visualization of the renal peritubular vessels. (2) Peritubular microcirculation shows a significant deterioration during ureteral obstruction. (3) Infusion of GRP may be beneficial for the microcirculation of the acutely obstructed kidney.

Aims: Cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) are frequently up-regulated in malignant tumours and play a role in proliferation, apoptosis, angiogenesis and tumour invasion. In the present study, the expression of COX-2 and VEGF in renal cell carcinoma (RCC) was analysed and correlated with the microvessel density (MVD). Methods and results: COX-2 and VEGF were analysed by realtime reverse transcriptase-polymerase chain reaction and immunohistochemistry. The MVD was assessed by CD31 immunohistochemistry. The expression of COX-2 and VEGF was determined in the RCC cell lines A498 and Caki-1 under short-term hypoxia and in multicellular tumour cell aggregates. COX-2 was expressed in RCC by tumour epithelia, endothelia and macrophages in areas of cystic tumour regression and tumour necrosis. COX-2 protein in RCC was not altered in comparison with normal renal tissue. VEGF mRNA was up-regulated in RCC and positively correlated with MVD. RCC with high up-regulation of VEGF mRNA showed weak intracytoplasmic expression of VEGF in tumour cells. Intracytoplasmic VEGF protein expression was negatively correlated with MVD. In RCC with necrosis the MVD was reduced in comparison with RCC without necrosis. A498 RCC cells down-regulated COX-2 and up-regulated VEGF under conditions of hypoxia. In Caki-1 cells COX-2 expression remained stable, whereas VEGF was significantly up-regulated. In multicellular A498 cell aggregates COX-2 and VEGF were up-regulated centrally, whereas no gradient was found in Caki-1 cells. Conclusions: COX-2 and VEGF are potential therapeutic targets because COX-2 and VEGF are expressed in RCC and associated cell populations such as endothelia and monocytes/macrophages.

Purpose. We investigated the feasibility of using flat panel volumetric computer tomography (fpVCT) for the detection of orthotopically implanted renal carcinomas in nude mice. Materials and methods. One million renal cell carcinoma cells [A-498 line (Braunschweig, Germany), in 0.2 ml phosphate-buffered solution (PBS), pH 7.4] were injected into the left kidney of each of the eight nude mice. Each mouse was imaged twice (12 and 16 weeks after implantation) with fpVCT (GE prototype with circular gantry with two 1024x1024, 200 mu m pixel size, aSi/CsI flat panel detector) after injection of 200 mu l contrast medium to check for tumour spread. After 16 weeks the mice were killed and dissected, and the imaging findings in liver, kidneys and lung were compared with the macroscopic findings. Results. No local evidence of tumour or of metastatic spread was seen on fpVCT after 12 weeks in any of the mice. After 16 weeks fpVCT revealed tumour growth in 6 of the 16 kidneys. Two mice had each developed a multifocal renal cell carcinoma and one mouse, a bilateral renal tumour manifestation. In one mouse liver metastases were seen. The fpVCT findings correlated well with the observations recorded in the pathological examination. Conclusion. fpVCT is an innovative and noninvasive imaging procedure that can be used for longitudinal investigation of tumour progression following orthotopic implantation of renal cell carcinoma to small animals. The use of a system of this kind will make a decisive contribution to reducing the number of animals used in experimental test projects.

Background. Octreotide (OCT) is used for the protection of pancreato-intestinal anastomoses and for treatment of acute pancreatitis. Its effect on jejunal microcirculation after ischemia-reperfusion has not been investigated. Material and methods. Intestinal ischemia was induced in Wistar rats (n = 8) by occlusion of the superior mesenteric artery for 40 min. Prior to reperfusion infusion of OCT (7.5 mu g/h) was started (n = 8). Microvascular perfusion of the jejunal mucosal and muscle layers was assessed and compared with that of groups without intervention (n = 16) by means of intravital microscopy, Results. Ischemia-reperfusion decreased mucosal functional capillary density from 838.4 +/- 12.6 to 418.9 +/- 9.6 cm(-1). Mucosal capillary red blood cell velocity was reduced from 0.53 +/- 0.01 to 0.35 +/- 0.01 mm/s (P < 0.05). Permanent leukocyte adherence was increased. OCT without ischemia-reperfusion decreased functional capillary density (735.4 +/- 13.5 cm(-1)) and red blood cell velocity (0.46 +/- 0.01 mm/s). After reperfusion OCT led to perfusion heterogeneity demonstrated by villous stasis (26 +/- 4%) and a decrease in the index of mucosal perfusion (0.38 +/- 0.02). Functional capillary density was further decreased compared with ischemic controls (234.0 +/- 11.8 cm(-1)). Capillary red blood cell velocity was lower (0.30 +/- 0.01 mm/s) than in ischemic controls. Conclusions. OCT impairs microvascular perfusion of the jejunum both under physiological conditions and after ischemia-repel fusion. (C) 2000 Academic Press.

The surgically induced split hydronephrotic kidney has been generally accepted as a valid model for the assessment of renal microcirculation by means of intravital microscopy. Whereas nearly all previous work on this issue has been done with a transillumination technique, we used an epiillumination model that is suitable for investigation of microvascular perfusion in both normal and hydronephrotic kidneys without surgical manipulation of the ureter. By means of the congenital unilaterally hydronephrotic Tauchi rat, microcirculation of the hydronephrotic and that of the nonhydronephrotic kidney were compared. For that purpose both the hydronephrotic and the nonhydronephrotic kidneys of Tauchi rats were exteriorized on a specially designed microscopy stage. After injection of FITC-dextran and rhodamine 6G, microvascular perfusion was assessed in both kidneys. The new model allowed visualization of arterioles, capillaries, and postcapillary venules in both the hydronephrotic and the nonhydronephrotic kidneys. Glomeruli could only be regularly seen in the hydronephrotic kidney, but also in some normal kidneys. Capillary blood cell velocity was significantly higher in the hydronephrotic kidneys (0.67 +/-0.03 mm/s) compared to the normal kidney (0.32 +/-0.05 mm/s; P<0.05), whereas capillary diameters were smaller (4.20.02 mum vs. 5.7 +/-0.2 mum; P<0.05). In addition, the hydronephrotic kidney showed a significantly lower density of perfused microvessels compared to the normal controls. Epiillumination intravital microscopy allows assessment of the cortical microcirculation in both the hydronephrotic and the nonhydronephrotic kidneys without surgical inductin of hydronephrosis. The hydronephrotic kidney shows significant microcirculatory differences compared to normal kidneys that should be taken into account when using a hydronephrotic model for pharmacological testing. (C) 2001 Academic Press.

Background. We investigated the effect of neurotensin and cholecystokinin (CCK) on intestinal microcirculation after ischemia-reperfusion. Method: Ischemia was induced in Wistar rats by occlusion of the superior mesenteric artery for 40 min. Ten minutes before reperfusion, infusion of either neurotensin or CCK was started. Afterwards. the microhemodynamics of the jejunum were examined by means of intravital microscopy. Results. Ischemia-reperfusion decreased functional capillary density from 873.4+/-18.1 to 362.5+/-8.3 cm(-1) and red blood cell velocity from 0.49+/-0.03 to 0.34+/-0.02 mm/s. Furthermore, leukocyte-endothelium interaction was increased. Neurotensin infusion significantly increased functional capillary density to 483.2+/-9.0 cm(-1) and red blood cell velocity to 0.69+/-0.01 mm/s in the mucosal capillaries compared with ischemic controls. Despite the amelioration of villus perfusion, the number of nonperfused villi significantly increased (11.8+/-3.6%) compared with ischemic controls. CCK infusion also resulted in a significant increase of functional capillary density (535.2+/-7.4 cm(-1)) and red blood cell velocity (0.67+/-0.01 mm/s). In contrast to neurotensin, the number of non-perfused villi was not increased (5.8+/-2.2%). Conclusion: We conclude that neurotensin further aggravates perfusion inhomogeneity and stasis when administered during the ischemic period. In contrast, CCK has no negative influence on perfusion homogeneity after ischemia-reperfusion. It may be superior to neurotensin in the reconstitution of normal microvascular perfusion patterns after ischemia-reperfusion.

Purpose: Renal cell cancer represents a suitable tumor model for in vivo observation of neo-angiogenesis. We used intravital microscopy and the well established dorsal skin fold chamber model to characterize neo-angiogenesis in freely implanted renal cell cancer spheroids. Material and Methods: Tumor spheroids were implanted into dorsal skin fold chambers of 8 nude mice. At days 3, 6, 10 and 14 after implantation the newly vascularized spheroid area, density of perfused microvessels in the spheroid versus the periphery, capillary center erythrocyte velocity and capillary diameter were recorded by intravital microscopy. Video images were analyzed by a computer assisted image analysis device. After the experiments the chambers were analyzed morphologically. Results. The model enabled quantitative analysis of microcirculation and angiogenesis in the renal cell cancer spheroids during 14 days of observation. Mean spheroid center perfused microvessel density +/- SEM increased from 3 +/- 2 to 269 +/- 21 cm.(-1) on days 3 to 10 and subsequently decreased to 189 +/- 38 cm.(-1) on day 14. Spheroid periphery perfused microvessel density was significantly higher throughout the experiments, attaining a mean maximum of 522 +/- 34 cm.(-1) on day 14. Mean capillary diameter decreased continuously from 14.2 +/- 0.9 to 8.4 +/- 0.4 mum. on days 3 to 14. In contrast, mean capillary center erythrocyte velocity significantly increased during 14 days of observation from 0.09 + 0.02 mm. per second on day 3 to 0.24 +/- 0.08 mm. per second on day 14. Histological analysis after 14 days revealed the spheroids as cell clusters in the upper layers of the dorsal skin fold chamber. Conclusions. The model is suitable for the analysis of renal cell cancer angiogenesis. Although it is heterotopic, angiogenesis in renal cell cancer spheroids mimics important characteristics of human renal cell cancer.

Xenin (1-25) has been detected in various locations in mammalians. It has structural similarities with neurotensin and its intestinal effects are claimed to be mediated by neurotensin receptors. It has been shown to influence gastrointestinal motility. The effects of xenin (1-25) on intestinal microvascular perfusion after ischemia/reperfusion have not been investigated yet. Therefore, the superior mesenteric artery was clamped for 40 min in Wistar rats (n = 8). Ten minutes prior to reperfusion, intravenous infusion of xenin (1-25) (5 nmol/kg/h) was started. By means of intravital microscopy, microvascular perfusion in the mucosal layer was assessed. Animals (n = 8) with and without clamping of the superior mesenteric artery and infusion of the carrier solution served as controls. After ischemia/reperfusion, xenin (1-25) increased the density of perfused microvessels and the capillary red blood cell velocity compared to ischemic controls. Capillary red blood cell velocity was elevated (p < 0.05). Xenin (1-25) improved the heterogeneous distribution of mucosal blood flow during reperfusion demonstrated by an increase of both the perfusion index and the percentage of perfused microvessels. We conclude that the effects of xenin (1-25) on intestinal microcirculation are significantly different from those previously described for neurotensin. A more complex effector mechanism must be postulated that may involve other regulatory peptides and receptors. (C) 2002 Elsevier Science B.V All rights reserved.

Purpose: Gastrin releasing peptide (GRP) is a growth factor for renal cell carcinoma (RCC) and it has vasoactive properties. Blockade of GRP receptor inhibits the growth of GRP receptor positive and negative tumors in nude mice, suggesting GRP effects other than those related to tumor epithelium. Therefore, in this study we analyzed the effects of GRP receptor blockade on neoangiogenesis in RCC. Materials and Methods: GRP receptor expression was determined in human RCC and corresponding normal tissue by real-time reverse transcriptase-polymerase chain reaction, immunohistochemistry and confocal laser scanning microscopy. Multicellular spheroids of the A498 RCC line were implanted into dorsal skin fold chambers of athymic nude mice. Neoangiogenesis was measured by intravital microscopy after blockade of GRP receptors by the GRP antagonist RC-3095. The influence of GRP on vascular endothelial growth factor secretion in A498 cells was studied in vitro. Results: GRP receptor expression was immunolocalized in tumor cells and microvessels. Implanted tumor cell spheroids and spheroid microvessels of the chamber also expressed GRP receptors. Spheroid neoangiogenesis was significantly inhibited by RC-3095 when given immediately after spheroid implantation. Vascular endothelial growth factor secretion of A498 cells was not affected by GRP. Conclusions: RCC angiogenesis is sensitive to GRP receptor blockade. Therefore, GRP receptors may not only stimulate tumor cell proliferation, but also affect tumor microcirculation.

After cystectomy two principal types of urinary diversion are used for the surgical reconstruction of the urinary tract: incontinent and continent. In the continent type of urinary diversion, a differentiation must be made between those with and without catheterization for voiding. Besides urothelial cancer other reasons for urinary diversion include neurogenic bladder palsy (connatal or acquired) due to meningomyelocele or connatal diseases like bladder exstrophy. The main objective of the clinical urologist when selecting urinary diversion are to achieve continence and to preserve upper urinary tract function. Knowledge of the different forms of urinary diversion is critical for the exact interpretation of the images. This review presents the typical imaging techniques after a description of the basic surgical features of urinary diversion. CT urography and MR urography are becoming increasingly important as further imaging tools for controlling urinary diversions.