肾缺血再灌流对大鼠肾乳头微循环的影响

缺血性急性肾衰(IARF)是临床休克的常见并发症。为探讨IARF时肾髓质微循环变化,本文活体观察了SD大鼠肾缺血再灌流对肾乳头微循环的影响。发现:肾动脉断流后,肾乳头先出现短暂性缺血苍白,继而直血     

生脉注射液减轻兔肾缺血再灌流损伤的作用研究

用自制的肾缺血再灌流损伤模型,在20只新西兰兔,研究了生脉注射液在肾缺血再灌流操作中的作用。结果表明:肾缺血再灌流24小时后,单纯缺血再灌流组动物血尿素氮和肌酐较缺血前显著升高;生脉防治组血尿素氮较缺血前显著升高,但肌酐无显著变化;在再灌流2小时和24小时,血中过氧化脂质(LPO)的含量,单纯缺血再灌流组较缺血前呈升高趋势,生脉防治组呈降低趋势,但差异均无显著性;再灌流24小时肾组织中LPO含量,生脉防治组较单纯缺血再灌流组肾脏呈严重坏死改变,生脉防治组仅有轻度变性。结果揭示:生脉注射液具有减轻兔肾缺血再灌流损伤的作用。     

血液浓、释对烫伤大鼠肾髓质活体微循环影响

本文活体观察了不同红细胞压积(HCT)大鼠烫伤后肾乳头直血管微循环改变。结果发现:不同HCT大鼠烫伤后均出现程度不同的直血管扩张、渗出、RBC聚集、血流速度减慢甚至部分停滞和流动直血管数(FVN)的减少。但其严重程度组间存在显著差异。其中血浓缩组(HCT55—60％)肾乳头微循环障碍明显重于正常(HCT46％)组;而血稀释组(HCT35—38％)较其它烫伤组微循环障碍明显改善。说明:血液浓、释对烫伤大鼠肾髓质微循环产生明显影响;血稀释治疗对改善烫伤引起的肾髓质微循环障碍,预防急性肾功能衰竭具有重要意义。     

犬肾血管构筑及血管和肾小管相互关系——扫描电镜观察

使用同时显示肾血管和肾小管扫描电镜法及肾血管铸型扫描电镜法,观察研究了犬肾血管构筑及肾血管和肾小管相互关系。血管球内存在亚小叶微循环单位;血管球内存在直捷通路;迷路部血管和肾小管无明显的逆流配置;球后血管在肾皮质内有广泛吻合;肾髓质次级血管束内一些降直血管具有门静脉特点;直血管在乳头部肾盂上皮下形成致密血管丛,它是升、降直血管间的主要连接通道;内髓升、降直血管间还有毛细血管及少量血管襻连接。本文还讨论了上述结构特点的功能意义。     

脂质过氧化在肾缺血和缺血再灌注损伤中的变化

本实验观察大鼠肾缺血75min及缺血60min后再灌注15min时肾组织脂质过氧化(LPO)和有关酶类变化。结果显示,肾脏缺血和缺血/再灌注后肾皮质和髓质中脂质过氧化产物丙二醛(MDA)含量均显著增高。超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)活性无明显变化。缺血/再灌注后黄嘌呤氧化酶(XO)活性显著升高。上述结果提示,肾缺血和缺血/再灌注时的LPO增强与氧自由基(OFR)产生增多有关。但上述二种情况时OFR产生机制不尽相同。     

缺血再灌流损伤对肾毛细血管内皮细胞的影响——细胞化 …

应用常规电镜及过氧化氢细胞化学技术，观察了缺血再灌流对鼠肾毛细血管内皮细胞损伤情况后，缺血６０ｍｉｎ可致毛细血管内皮细胞明显肿胀，过氧化氢细胞化学表现为在内皮细胞表面有少量电子致密的沉积缺血６０ｍｉｎ复流１０ｍｉｎ毛细血管内皮细胞表面有大量电子致密物沉积，缺血６０ｍｉｎ复流３０ｍｉｎ及６０ｍｉｎ内皮细胞损伤加重，毛细血管内皮细胞与基底层之间裂开，翻起，甚至剥脱。毛细血管内皮细胞与肾小管上皮细胞之间     

烫伤大鼠肾皮、髓质血流的变化

用ＬＤＦ－３型激光多普勒血流计分别测定重度皮肤烫伤大鼠肾皮、髓质烫伤前后血流变化。结果发现：伤后５ｍｉｎ，肾皮、髓质血流均严重下降。分别降至伤前的６０％和５２％；继而皮质血管呈现明显的节律运动。伤后３０ｍｉｎ，皮质血流随动脉血压代偿性回升呈明显增加趋势，而髓质血管节律性运动不明显，其血流也不随血压代偿性回升而增加，呈持续减少趋势。上述结果表明：重度皮肤烫伤大鼠肾皮、髓质血流均明显下降，但以髓质为著；髓质血管自律性运动较皮质差。在病理情况下，髓质血供具有更大的易损性。     

肠道缺血再灌流对肾内源性碱性成纤维细胞生长因子和转化生长因子β基因表达的影响

目的和方法:研究肠道缺血再灌流过程对肾脏内源性碱性成纤维细胞生长因子(bFGF)和转化生长因子β(bTGFβ)基因表达的影响.采用肠系膜上动脉夹闭45min与再灌流6 h和24 h动物模型,用原位杂交与逆转录PCR(RT-PCR)技术研究两种生长因子基因在正常、缺血以及再灌流肾组织中的表达.结果:两种因子的mRNA在正常肾脏均有少量表达.缺血45min后,两种因子基因表达减少.再灌流6 h,肾组织中TGFβ基因表达明显增加,而bFGF基因表达仍然较少.再灌流24 h,两种因子基因表达恢复至正常对照.结论:肠道缺血再灌流可以引起肾组织内源性bFGF与TGF β基因表达的改变,这种变化过程与肾缺血性损伤后自我修复机制密切相关.     

大鼠肾缺血后肾小管上皮及血管内皮细胞超微结构改变

目的：通过电子显微镜观察大鼠。肾小管上皮细胞及肾髓质毛细血管内皮细胞缺血损伤情况。方法：大鼠肾动脉钳夹30、60min,再灌流24h。取肾组织块进行电子显微镜观察。结果：缺血30、60min,肾小管上皮细胞肿胀明显,毛细血管内皮细胞也肿胀,但2组超微结构观察无明显差别；缺血60min再灌流24h,大部分肾小管上皮细胞坏死,毛细血管内皮细胞脱落、肿胀及坏死；缺血30min再灌流24h,部分肾小管上皮细胞坏死或凋亡,毛细血管内皮细胞也有凋亡。结论：缺血损伤的严重程度与细胞死亡方式有关,对电镜观察细胞坏死、凋亡注意点及坏死与凋亡的关系进行了讨论。     

自由基在肾缺血再灌流损伤中作用的实验研究

本实验选用大鼠右肾切除、左侧肾蒂夹闭60min肾缺血模型,观察缺血、再灌流、再灌流加别嘌呤醇(AP)和再灌流加超氧化物歧化酶(SOD)对动物血清肌酐(Scr)、肾系数和肾形态学变化的影响。结果发现60min肾缺血后再灌流24hr,动物的Scr水平明显高于单纯缺血组动物的水平(P<0.01)和假手术组动物的水平(P<0.01);光镜下肾组织损伤较单纯缺血组动物明显加重,表明再灌流可以加重缺血肾损伤,动物发生缺血性急性肾衰(IARF)。给AP和SOD处理后,肾衰动物的Scr水平、肾系数分别较单纯再灌流组动物明显降低(P<0.01)。整个肾组织病变尤其是线粒体病变、刷状缘损伤大为减轻。说明AP和SOD可以减轻IARF,自由基可能参于肾缺血再灌流损伤,膜和线粒体损伤可能是IARF发病的重要因素。     

Hydraulic and oncotic pressure measurements in inner medulla of mammalian kidney.

The vasa recta are thought to play an important role in the transfer of water andsolutes within the renal medulla. Hydraulic pressures were measured in vasa recta onthe surface of the exposed papilla in young Munich Wistar rats, and blood was collected from these microvessels for determination of total protein concentration and calculation of colloid oncotic pressure. In descending vasa recta at the base of the exposed papilla, mean hydraulic pressure was 9.2 plus or minus 0.4 (SE) mmHg and plasma protein concentration averaged 7.1 plus or minus 0.4 g/100 ml. Corresponding valuesin ascending vasa recta at the same level were 7.8 plus or minus 0.4 mmHg and 5.6 plusor minus 0.3 g/100 ml. respectively. The protein concentrations correspond to calculated oncotic pressures of 26 and 18 mmHg in descending and ascending vasa recta, respectively. We interpret these findings as evidence for net water uptake by the vasa recta in the renal inner medulla for which the driving forces are the transcapillary hydraulic and oncotic pressure differences.     

Outer medullary circulatory defect in ischemic acute renal failure.

Changes in medullary circulation may contribute significantly to the pathogenesis of ischemic acute renal failure. The microcirculation of the outer medulla of the rat kidney was studied by morphometry, carbon injection, and scanning electron microscopy of vascular casts after temporary renal ischemia. Morphometry showed a markedly reduced vascular area and an increased tubular epithelial cell area in the outer stripe of the medulla 2 hours after blood reflow. Maximum diminution in vascular area occurred 24-48 hours after reflow, with swollen and later necrotic tubular epithelium compressing the surrounding vascular compartment. Outflow blockade of venous vasa recta in the outer stripe caused congestion of the inner stripe. Carbon injection and scanning electron microscopy of vascular casts confirmed the perfusion defects of the outer stripe. These results suggest that decreased blood reflow to the outer stripe of the medulla secondary to tubular epithelial cell swelling and necrosis plays a significant role in the pathogenesis of ischemic acute renal failure in the rat.     

A Mathematical Model of Renal Blood Distribution Coupling TGF, MR and Tubular System

Objective：To investigate the relationship between renal blood distribution and the physiological activities of the kidney. Methods：A mathematical model is developed based on response （MR） Hagan-Poiseuille law and mass transport, coupling mechanics of myogenic tubuloglomerular feedback （TGF） and the tubular system in the renal medulla. The model parameters, including the permeability coefficients, the vascular lumen radius and the solute concentration at the inlet of the tubes, are derived from the experimental results. Simulations of the blood and water flow in the loop of Henel, the collecting duct and vas rectum, are carried out by the model of the tubular system in the renal medulla, based on conservations of water and solutes for transmural transport. Then the tubular model is coupled with MR and TGF mechanics. Results：The results predict the dynamics of renal autoregulation on its blood pressure and flow, and the distributions are 88.5% in the cortex, 10.3% in the medulla, and 1.2% at papilla,respectively. The fluid flow and solute concentrations along the tubules and vasa recta are obtained. Conclusion ：The present model could assess renal functions qualitatively and quantitatively and provide a methodological approach for clinical research.     

Evidence for an acid pH in rat renal inner medulla: paired measurements with liquid ion-exchange microelectrodes on collecting ducts and vasa recta

We reevaluated the pH in the renal medulla in rats. pH of the vasa recta blood was about 1 pH unit acidic in comparison to the pH of renal artery blood. During furosemideinduced diuresis pH of vasa recta blood increased whereas pH of collecting duct urine further decreased. The acidic pH in the rat renal inner medulla during antidiuresis raises important questions about the source of H⁺ in inner medulla.     

Videomicroscopic method for direct determination of blood flow to the papilla of the kidney

We adapted the technique of videomicroscopy for direct determination of blood flow in individual capillaries of the papilla of the kidney, the ascending vasa recta (AVR) and descending vasa recta (DVR). The papilla was exposed in anesthetized rats and positioned under a video-camera-microscope and viewed under epi-illumination. The intravenous infusion of fluorescein-isothiocyanate (FITC)-labeled gamma globulin was combined with fluorescence microscopy to enhance the contrast among plasma, red blood cells and capillary walls. On the television monitor, the walls were clearly outlined, enabling the measurement of capillary diameter. The velocity of red cells (V _rbc ) in individual vasa recta was measured using the dual slit technique. From the videotape recorded microscopic image of a vas rectum, two photometric signals were obtained by integrating the light intensity from two electronic “windows” positioned closely together over the same capillary. Red cell velocity was calculated by dividing the distance between the two windows by the time delay between signals. The delay was determined using analog correlation tracking or digital cross correlation techniques. Single vasa recta blood flow was calculated from capillary diameter, V _rbc , and F (Fahraeus factor), which converts V _rbc to average whole blood velocity, V _blood . In quartz capillaries the same size as vasa recta, the ratio F=V _rbc /V _blood =1.42±0.06. Total papillary blood inflow and outflow was calculated by multiplying the total number of DVR or AVR times the mean single capillary blood flow for DVR or AVR, respectively. Dr. Zimmerhackl is a Research Fellow of the National Kidney Foundation and the National Kidney Foundation of Northern California.     

The source of inulin in samples of vasa recta blood

Vasa recta blood was sampled from the exposed renal papillae of 11 Munich-Wistar rats (Group I). The mean vasa recta plasma-to-systemic plasma (VR/P) inulin concentration ratio was 5.4±1.2 (SE), which is significantly higher than the mean VR/P protein ratio previously reported (1.74 in descending vasa recta and 1.38 in acending vasa recta). Even if glomerular and vasa recta capillaries are as impermeable to inulin as to protein, VR/P inulin concentration ratios should not exceed VR/P protein concentration ratios, unless inulin is added to vasa recta from an extracapillary source. To determine if inulin can permeate the epithelial lining of the papilla, we bathed exposed papillae with concentrated inulin solutions (5 rad 10 g/ 100 ml). In 7 rats (Group II) the inulin concentration in 23 VR plasma samples ranged from 0 to 492 mg/100 ml, exhibiting large variations within individual rats. A third group of 12 rats, infused intravenously with inulin, exhibited the same pattern of variability. We interpret these data as evidence for occasional contamination of vasa recta blood by urine in adjacent collecting tubules or bathing the papilla. A preliminary report of this investigation was presented to the Western Society for Clinical Research, Carmel, California, February, 1976.     

Dynamic simulation of the renal medulla

The operation of the urinary concentrating system is intimately linked to the complex and distinctive anatomy of the renal medulla, and research into the concentrating mechanism has stimulated considerable endeavour in modelling of the process. The paper presents a dynamic model of the renal medulla which attempts to describe concentrations and axial flows in two sets of tubes, one comprising the loop of Henle and collecting duct and the other comprising the descending and ascending vasa recta, and in the interstitial space. Particular attention is given to modelling of the characteristics of the inner medulla. The model allows for the tapering of the inner medulla towards the papilla, the union of collecting ducts and the fact that nephrons and vascular loops turn back at various depths so that only a small portion of them reach the papilla. The inclusion of this detail in the model leads to a good representation of the concentrating mechanism and the model provides a good basis for the study of phenomena such as sodium reabsorption.     

缺血预处理对缺血/再灌注脑的保护及其与微循环调节功能的关系研究

目的:探讨缺血预处理(IPC)是否对缺血/再灌注(I/R)脑细胞具有保护效应及其与微循环调节功能间的关系。方法:I/R与IPC组大鼠均复制脑I/R损伤模型,IPC组增加于I/R之前24h进行的短暂脑缺血预处理。动物均开颅窗观察缺血前、缺血后、再灌后脑软膜微循环指标;并取脑组织作红四氮唑(TTC)染色观察缺血损伤情况。结果:I/R组TTC染色后大多数出现不规则的缺血损伤的淡染区,而IPC组明显少见。IPC组缺血及再灌之后毛细血管累计总长度、微循环血流量、微血管内血流速度之相对增加值均大于I/R组。I/R组于再灌注之后有无复流现象;而IPC组此时呈灌注增加的过程。结论:IPC通过提高微循环的调节功能,促进毛细血管的相对性开放和血流的相对性加快,减轻缺血期组织血流低灌注和再灌注期无复流现象,从而对I/R脑产生一定保护作用。