Cytoplasmic sequestration phenomena in smooth muscle cells of kidney resistance vessels and epithelioid cells of the juxtaglomerular apparatus

Summary The occurrence of vacuoles in cells of contractile tissues and especially in media cells of resistance vessels has been known for quite some time. Recently, it has been widely accepted that these vacuoles, characteristically lined by a double membrane, result from herniation of one vascular smooth muscle cell into the other as a result of vasoconstriction. In our electronmicroscopic investigations we found double membrane-bounded vacuoles not only in kidney resistance vessels of rats and mice under conditions of vasoconstriction, but also in control animals and animals with maximal renal vasodilation. Part of our observations are compatible with the assumption that such vacuoles arise from a damage of club-shaped, musculo-muscular contacts due to shape changes of media cells during maximal vasoconstriction or vasodilation. However, serial thin sectioning revealed that some of the cytoplasmic vacuoles have no connections with neighbouring cells. This finding and various parallels to the generation of autophagic vacuoles indicate that the so-called herniations may also represent demarcations of large cytoplasmic areas within an individual cell. Irrespective of the origin of these vacuoles, their contents show different stages of deterioration. At later stages, the vacuoles appear to be adjacent, with only one membrane, to the extracellular space, into which they are believed to discharge finally. Cytoplasmic vacuolization has not only been observed in smooth muscle cells, but also in juxtaglomerular epithelioid cells of the afferent arteriole. Here the vacuoles - besides other organelles - also contain secretory granules; it is therefore proposed that autophagic phenomena with final extrusion of cytoplasmic material may be involved in the programmed down-regulation of the granular renin store following inhibition of renin synthesis and secretion.These studies were supported by the German Research Foundation within the Forschergruppe Niere, Heidelberg     

Hypothesis that embolization is an important mechanism in the laser destruction of cutaneous vascular lesions

It is hypothesized that laser-induced red blood cell aggregations form emboli that assist in the therapeutic effect of lasers on vascular lesions.     

Arteriolar Dilation Produced by Venule Endothelium-Derived Nitric Oxide

Objective: We conducted bioassay experiments to determine whether nitric oxide produced by endothelial cells (endothelial-derived nitric oxide, or EDNO) within large venules could act to dilate arterioles. Methods: In these experiments, parallel segments of first-order arterioles and venules were isolated from skeletal muscle and were cannulated in series with a glass connecting tube (length: 300–500 μm). Arterioles were mechanically denuded of endothelium by a delicate yet abrasive rubbing technique. Venular endothelium remained intact. Endothelial denudation of arterioles was confirmed by the absence of dilation during exposure to acetylcholine (10^?6 mol/L). The cannulated vessels were pressurized to 30 cm H₂O and the arterioles preconstricted by approximately 50% with norepinephrine (10^?10 mol/L). Results: Topical applications of acetylcholine (10^?6 mol/L) or bradykinin (10^?9 mol/L) during luminal perfusion from venule to arteriole produced significant arteriolar dilation. In contrast, a slight arteriolar constriction was observed when the direction of flow was reversed (i.e., arteriole to venule) in the presence of either acetylcholine (10^?6 mol/L) or bradykinin (10^?9 mol/L). Inhibition of venular EDNO with; N^C-monomethyl-L-arginine (L-NMMA; 10^?5 mol/L; 1 hour) completely abolished the arteriolar dilation observed in response to acetylcholine or bradykinin during venule to arteriole perfusion. Conclusions: These results demonstrate that venular-derived EDNO can relax arteriolar vascular smooth muscle.     

犬肾动脉栓塞DSA成像技术的改进

本实验使用丝裂霉素c白芨胶行犬肾动脉栓塞，将30条犬随机分MMC白芨胶，MMC碘油，MMC白芨胶＋白芨、单纯白芨胶，MMC稀白芨胶、MMC溶液，对照7组。着重讨论大肾动脉栓塞前后DSA成像问题，指出了合理使用麻醉剂、安定、抑制肠蠕动等药物，以及犬腹部加压，选用DSA的TID程序，可望获得高质量的DSA图像。     

不同浓度丙泊酚通过缝隙连接通讯对舒张大鼠肠系膜动脉的影响

目的观察丙泊酚对SD大鼠肠系膜动脉的影响和对肠系膜动脉舒张作用是否与缝隙连接通讯相关。方法应用压力肌动图技术,在急性分离的SD大鼠肠系膜动脉2级血管上,观察1×10-7、3×10-7、1×10-6、3×10-6、1×10-5、3×10-5、1×10-4和3×10-4 mol/L丙泊酚对血管直径的影响,预孵育缝隙连接阻断剂18-β甘草次酸(18β-glycyrrhetinic acid,18β-GA)和2-aminoethoxydiphenylborate(2-APB)后,观察丙泊酚对血管直径的影响。结果给予1×10-7、3×10-7、1×10-6、3×10-6、1×10-5、3×10-5、1×10-4和3×10-4 mol/L的丙泊酚,使SD大鼠血管直径从(208.6±13.4)μm分别增加至(213.5±13.6)、(219.7±13.2)、(226.4±12.5)、(234.9±12.3)、(245.5±13.0)、(267.4±15.2)、(336.2±18.3)和(385.9±14.2)μm,1×10-4 mol/L的丙泊酚引起血管直径随着丙泊酚浓度增大而增加(P0.01)。分别预孵育18β-GA和2-APB后,1×10-4 mol/L的丙泊酚对大鼠肠系膜动脉舒张作用明显减弱(P0.01)。结论丙泊酚呈浓度依赖性舒张肠系膜动脉,其作用机制可能与缝隙连接通讯相关。     

视网膜动脉平滑肌细胞中大电导钙离子激活钾通道电流和钙离子浓度变化对糖尿病视网膜动脉收缩的影响

背景 糖尿病视网膜病变(DR)是常见的视网膜微血管并发症,视网膜血管平滑肌细胞大电导钙激活钾离子通道(BK)是调节血管舒缩和血液动力的主要因素.目前关于视网膜动脉平滑肌细胞(RASMCs)上BK通道的功能变化在DR形成中的作用鲜有研究报道. 目的 研究正常及糖尿病模型大鼠RASMCs中BK通道电流、钙离子浓度及不同钙离子浓度下BK通道开放概率(NP0)的变化,探讨DR早期的血管损伤机制. 方法 采用随机数字表法将50只SPF级8～12周龄SD大鼠随机分为正常对照组和糖尿病模型组,糖尿病模型组40只大鼠腹腔内注射60 mg/kg链脲佐菌素(STZ)法制作1型糖尿病模型,正常对照组大鼠10只同法注射枸橼酸钠溶液.采用酶消化法分离大鼠RASMCs,应用全细胞膜片钳技术记录大鼠RASMCs中BK通道电流;采用荧光探针法测定大鼠RASMCs内钙离子浓度;采用膜内向膜外型单通道膜片钳技术记录不同钙离子浓度条件下RASMCs中BK单通道NP0的变化.结果 36只大鼠糖尿病造模成功,造模成功率为90％.刺激电压大于60 mV时,糖尿病模型组大鼠RASMCs中BK通道电流密度明显下降,刺激电压为100 mV时,正常对照组和糖尿病模型组大鼠RASMCs BK通道电流分别为(100±23) PA/PF和(50±7) PA/PF,差异有统计学意义(t=19.80,P＜0.05).当加入BK通道特异性阻滞剂非洲蝎毒素100 nmol后,正常对照组的BK通道电流明显减弱,而糖尿病模型组BK通道电流无明显变化;正常对照组和糖尿病模型组大鼠RASMCs内钙离子浓度分别为(123±11)nmol/L和(255士10)nmol/L,差异有统计学意义(t=32.50,P＜0.05).在刺激电位为60 mV条件下,随着钙离子浓度增加,BK通道NP0增加,差异有统计学意义(F=15.28,P＜0.05).结论 糖尿病模型大鼠RASMCs中BK通道电流下降,细胞内钙离子浓度升高,BK单通道NP0下降.BK通道功能改变可能是导致糖尿病时视网膜动脉异常收缩的主要原因之一.