低频超声破坏微泡造影剂开放血脑屏障的实验研究

目的探讨不同强度的低频超声经颅诱导微泡造影剂破坏对大鼠血脑屏障的影响。 方法股静脉注入微泡造影剂后，采用频率43kHz，声强分别为1．2．1．5．1．8．2．3w／cm。的连续超声波经大鼠颅骨照射3min，荧光显微镜观察伊文思兰的渗出。 结果注射微泡造影剂后，声强1．2w／cm^2时超声波即可以开放血脑屏障，随声强的增加脑组织损伤加重。 结论低频超声诱导微泡造影剂破坏可以靶向开放血脑屏障。     

两种微泡造影剂开放大鼠血脑屏障的比较性研究

目的 探讨自制磷脂微泡和声诺维两种微泡对大鼠血脑屏障的影响.方法 将32只SD大鼠随机分为自制微泡即刻组、自制微泡24 h组、声诺维即刻组和声诺维24 h组,各组由尾静脉注射相应微泡后,在探头频率为1 MHz、声强4 W/cm2、辐照时间1.0 min参数下超声照射大鼠脑部,大体观察脑组织的蓝染程度及范围;伊文思蓝测定法观察大鼠血脑屏障通透性;光镜下观察脑组织、脑细胞和血脑屏障病理学改变.结果 声诺维24 h组大鼠脑组织蓝染程度及范围明显小于其他各组,脑组织通透性明显低于其他各组（P﹤0.05）,HE染色各组未见大鼠脑组织损伤及血细胞渗出.结论 自制磷脂微泡开放大鼠血脑屏障效果与声诺维相比无明显差异,且自制微泡开放血脑屏障的效果更为稳定.     

低频超声联合微泡经颅开放血脑屏障初步研究

目的探讨低频超声联合微泡经颅靶向开放血脑屏障及在临床应用价值。方法①经静脉注射微泡后,用频率为43kHz、强度为2W/cm2,持续超声波辐射大鼠头部5min;②采用荧光显微镜伊文氏蓝(EB)、电镜镧示踪法以及透射电镜观察脑组织的超微结构变化。结果经颅超声波与微泡联合能短暂地促进伊文氏蓝和镧离子通过多种形式跨越血脑屏障。结论低频超声联合微泡能可逆的、靶向的、局部的开放血脑屏障,并为进一步研究药物进入脑实质内提供新的策略。     

超声微泡造影剂对心肌组织毛细血管通透性的影响实验研究

目的　研究超声破坏微泡造影剂对靶区内心肌组织毛细血管通透性的影响 ;探讨超声微泡造影剂增强基因转染的机制。方法　 2 4只健康雄性 Wistar大鼠 ,取 15只分为 3组 ,第 1组经静脉输入含有伊文思蓝 (Evans blue,EB)的微泡造影剂 ,并采用超声波在鼠胸壁辐照约 6 min破坏心肌组织内造影剂 ;第 2组采用超声照射 ,同时经静脉单纯输入 EB溶液 ;第 3组单纯经静脉输入 EB作为对照。照射完毕 2 h后放血处死大鼠 ,使用标准曲线和分光光度法测量各组大鼠心肌组织中 EB含量 (作为反映血管通透性的指标 )。另 9只大鼠随机分为 3组 ,每组 3只。第 1组经静脉输入微泡造影剂 ,并采用超声波在鼠胸壁辐照约 6 min破坏心肌组织内造影剂 ;第 2组单纯采用超声照射 ;第 3组不加任何处理 ,作为对照。照射完毕即刻处死大鼠 ,取心肌组织进行电镜观察毛细血管的改变。结果　采用超声照射 ,并经静脉输入微泡造影剂的大鼠 ,心肌组织中 EB含量为 (75 .33± 16 .80 )μg/ g,比单纯超声照射[(32 .2 1± 9.5 3)μg/ g]及心肌正常组织 EB含量 [(37.16± 7.98)μg/ g]明显增加 (P<0 .0 5 )。电镜结果显示超声破坏微泡后 ,能使毛细血管破裂 ,红细胞溢出于毛细血管外。结论　超声波触发破坏微泡造影剂后能使心肌组织毛细血管通透性增加 ,可     

超声破坏微泡对心肌细胞膜通透性影响的研究

目的探讨超声破坏微泡造影剂对心肌细胞膜通透性的影响。方法将15只昆明小白鼠随机分为3组,一组采用尾静脉输入白蛋白微泡造影剂,胸壁用频率为1MHz,强度为1.5W/cm2的超声进行辐照1min;一组单纯采用同等超声辐照相同时间;一组作为对照。作用后即刻取心肌组织用硝酸镧(La)示踪法做透射电镜观察心肌细胞膜通透性的变化。结果采用超声破坏微泡后可见部分镧颗粒分布于心肌细胞胞浆内,部分分布于线粒体外、细胞核外;单纯超声作用组心肌细胞胞浆中可有少量的镧颗粒分布,而大部分镧颗粒分布于细胞膜外;而对照组镧颗粒分布于心肌细胞膜外。结论超声破坏微泡可提高心肌细胞膜通透性,可能是超声微泡造影剂增强组织中基因转染的机制之一。     

脑超声造影中超声造影剂剂量对血脑屏障通透性的影响

目的探讨不同剂量超声造影剂在超声造影中对血脑屏障通透性的影响。方法60只清洁级SD大鼠,给予相同机械指数的超声进行辐照,并经尾静脉注射不同剂量的“脂氟显”超声造影剂,观察超声照射后血脑屏障通透性的变化。结果在造影剂剂量为50μl/kg时,血脑屏障通透性即与对照组相比产生显著性统计学差异,且随着超声造影剂剂量的增加其引起血脑屏障通透性也随之增加。结论在相同能量强度超声场中,超声造影剂微泡数目是引起不同生物学效应的重要因素。     

超声波介导微泡破裂促EGFP基因转染大鼠脑组织的实验研究

目的 探讨超声波介导微泡造影剂破裂促外源基因在中枢神经系统转染的可行性.方法 15只大鼠分3组,1组经股静脉输入含绿色荧光蛋白质粒(pEGFP)的造影剂0.8 ml,立即用超声波照射大鼠颅骨3 min;第2组输入相同的造影剂0.8 ml,不采用超声波照射;第3组输入不含造影剂的pEGFP 0.2 ml,立即超声波照射3 min.48 h后处死大鼠,荧光显微镜下观察绿色荧光蛋白表达.结果 只在股静脉输入含pEGFP的造影剂,并经超声波照射的大鼠微血管壁上观察到绿色荧光蛋白表达.结论 以微泡造影剂为基因载体,通过超声波靶向破坏微泡,有可能在脑血管内皮细胞中获得基因转染.     

超声微泡造影剂对心肌组织的生物学效应及介导VEGF基因转染大鼠心肌的实验研究

目的 探讨超声微泡造影剂对心肌组织的生物学效应及其介导VEGF基因转染大鼠心肌的有效性。方法 18只健康雄性Wistar大鼠，取3只采用超声波在鼠胸壁破坏微泡造影剂，观察对心肌组织显微结构的影响。将另15只急性心肌梗死3天后的雄性Wistar大鼠分为3组，每组5只。第一组采用超声破坏微泡造影剂的方式，将pcDzVEGFm基因转染大鼠心肌至造影剂不再显影(约6min)；第二组尾静脉输入同等剂量携pcD。VEGF。基因的造影剂；第三组为对照。2周后，取缺血心肌组织行VEGF免疫组织化学染色，观察心肌组织血管内皮生长因子(VEGF)蛋白表达情况。结果超声波破坏微泡造影剂能使心肌组织充血，产生大量空泡，并有部分心肌细胞坏死。采用超声微泡造影剂介导的VEGF基因转染，能明显增强大鼠心肌组织VEGF蛋白的表达。结论 超声微泡造影剂能明显增强对组织的空化效应，其介导的VEGF基因治疗是一种无创、新型、高效的基因转移方法。     

诊断超声联合微泡靶向开放单侧大鼠血脑屏障的初步研究

目的初步探讨诊断超声靶向击破微泡开放大鼠单侧血脑屏障通透性的可行性、有效性及安性。方法25只健康SD大鼠,诊断超声经颞骨照射单侧大脑半球,对侧大脑半球作对照。对伊文思蓝外渗范围进行分级和萃取定量。透射电镜观察硝酸镧分布评价血脑屏障超微结构变化,并对双侧脑实质的病理损伤进行评价和分级。结果照射侧大脑半球可见以海马为中心的片状均匀伊文思蓝渗出,而对侧脑实质未见渗出;透射电镜照射侧大脑半球硝酸镧渗出血管并分布于神经纤维间隙,而对照侧未见硝酸镧外漏;超微结构显示少量神经元轻度肿胀。病理组织学观察照射侧大脑半球可见少量红细胞外漏,未见明显组织细胞损伤。结论诊断超声靶向击破微泡能安全有效靶向开放单侧大鼠血脑屏障且呈海马为中心分布,这对于颅内以海马为中心分布疾病的靶向性药物治疗具有潜在的临床价值。     

超声微泡造影剂对心肌组织的生物学效应及介导VEGF基因转染大鼠心肌的实验研究

目的探讨超声微泡造影剂对心肌组织的生物学效应及其介导VEGF基因转染大鼠心肌的有效性. 方法 18只健康雄性Wistar大鼠,取3只采用超声波在鼠胸壁破坏微泡造影剂,观察对心肌组织显微结构的影响.将另15只急性心肌梗死3天后的雄性Wistar大鼠分为3组,每组5只.第一组采用超声破坏微泡造影剂的方式,将pcD2VEGF121基因转染大鼠心肌至造影剂不再显影(约6min);第二组尾静脉输入同等剂量携pcD2VEGF121基因的造影剂;第三组为对照.2周后,取缺血心肌组织行VEGF免疫组织化学染色,观察心肌组织血管内皮生长因子(VEGF)蛋白表达情况.结果超声波破坏微泡造影剂能使心肌组织充血,产生大量空泡,并有部分心肌细胞坏死.采用超声微泡造影剂介导的VEGF基因转染,能明显增强大鼠心肌组织VEGF蛋白的表达.结论超声微泡造影剂能明显增强对组织的空化效应,其介导的VEGF基因治疗是一种无创、新型、高效的基因转移方法.     

Effects of transcranial ultrasound and intravenous microbubbles on blood brain barrier permeability in a large animal model

We sought to determine whether transtemporal-applied 1-MHz ultrasound-induced microbubble destruction may be a safe method of transiently altering blood brain barrier (BBB) permeability for drug delivery in a large animal model. Endothelial cells are an integral component of the BBB but also prevent passage of potentially therapeutic drugs. Ultrasound-mediated destruction (UMD) of microbubbles has been shown to disrupt this barrier in small animals when ultrasound is delivered through bone windows. However, the effects of temporal bone attenuation and scattering in a large animal may limit the clinical application of such a technique. Twenty-four pigs were studied. One-MHz pulsed-wave ultrasound at 2.0 W/cm(2) (20% duty cycle) across the temporal bone was applied for 30 min after intravenous injections of either albumin-coated perfluorocarbon microbubble (PESDA, 8 pigs), lipid-encapsulated perfluorocarbon microbubbles (LEMB, 8 pigs) or ultrasound alone (8 pigs). BBB leak was quantified at 30 and 120 min after insonation using Evans blue. Serial magnetic resonance imaging (MRI) was performed in nine of the pigs (3 for each group) to quantify Gadolinium leak within the parenchyma. Peak negative pressures decreased ten-fold when ultrasound was transmitted across the pig temporal bone. Despite this, spectrophotometric analysis showed that both IV LEMB and PESDA combined with transtemporal ultrasound resulted in a significant increase in Evans blue extravasation across BBB of the treated side at 30 min after insonation (p < 0.001; compared with ultrasound alone) but not at 120 min. There was significant retention of Gadolinium within the insonified parenchyma at 60 and 90 min after insonation, but not at 120 min. Oxygen saturation and arterial pressures were not changed after any microbubble injection. Intravenous microbubbles, combined with transtemporal ultrasound, can transiently increase BBB permeability in a large animal. This induced opening of BBB is reversible and may be a safe noninvasive method of achieving drug or gene delivery across the BBB.     

超声微泡转染前列腺癌细胞的参数筛选

目的观察不同辐照参数下超声微泡对前列腺癌细胞生长及基因转染效率的影响。方法采用噻唑兰比色法检测单纯超声、单纯微泡、超声辐照微泡对前列腺癌细胞生存率的影响。荧光显微镜观察超声微泡介导的质粒为EGFP基因与HSV l-TK基因共表达载体。观察它对前列腺癌细胞PC-3转染后荧光表达情况,Westernblot检测EGFP蛋白的表达情况。结果 MTT显示超声强度为1.0W/cm2,频率为1MHz,辐照时间30s时超声辐照对细胞无明显的抑制作用;采用不同浓度的微泡对前列腺癌细胞PC-3作用24h后,各实验组细胞存活率与对照组比较差异无统计学意义(P>0.05);当采用最适的超声辐照时间辐照微泡浓度为10、20、40、80μL时,超声+微泡(80μL)组细胞存活率低,与对照组相比差异有统计学意义(P<0.05),而10、20、40μL组中细胞生长良好;转染EGFP后48h,在荧光显微镜观察对照组未见荧光表达,其他各组中均有荧光表达,并随着微泡剂量的增加,荧光表达量增多;Western blot检测显示各处理组中均有EGFP蛋白的表达,超声+微泡(20μL)+TK(1μg)组、超声+微泡(40μL)+TK(1μg)组的EGFP蛋白表达明显高于其他各组。结论在最适辐照参数下,超声微泡造影剂能够有效地促进TK基因的转染。     

Focused Ultrasound Microbubble Destruction‐Mediated Changes in Blood‐Brain Barrier Permeability Assessed by Contrast‐Enhanced Magnetic Resonance Imaging

Objective. The purpose of this study was to use enhanced magnetic resonance imaging (MRI) to evaluate the changes of blood‐brain barrier (BBB) permeability in target and nontarget areas of rabbit brains after BBB disruption induced by focused ultrasound‐mediated microbubble destruction. Methods. Focused ultrasound (1.1 MHz) in combination with a sulfur hexafluoride microbubble contrast agent was applied at 2 or 3 target locations in 1 hemisphere of 29 rabbit brains to induce BBB disruption. The opposite side was used as a control, and a normal group contained another 14 rabbits that did not undergo sonication. The MRI signal intensity enhancement in the target locations was detected to evaluate gadolinium (Ga) retention after sonication, and extravasation of Evans blue (EB) dye was detected to evaluate the BBB disruption quantitatively at different times after sonication (0.5, 2, 4, 6, 8, and 24 hours and 1 week). Results. Compared with the control group, Ga retention, changes in EB content, and extravasation in the cerebral cortex of the sonicated group peaked at 2 hours (P < .01) and decreased to the normal level 8 hours after sonication (P < .01). There was no visual evidence of injury or hemorrhage within the brain parenchyma of all of the rabbits' treated hemispheres. Conclusions. Magnetic resonance imaging–guided focused ultrasound can disrupt the BBB reversibly and can allow targeted delivery of some molecules that normally cannot cross the BBB to locations in the brain. Changes in BBB permeability develop within minutes after sonication as a result of a combination of factors. The BBB has a self‐repairing characteristic, which is activated after ultrasound sonication. This may offer an improvement in future clinical applications for central nervous system diseases.     

Focused Ultrasound and Microbubble Treatment Increases Delivery of Transferrin Receptor-Targeting Liposomes to the Brain

The blood-brain barrier (BBB) is a major obstacle to treating several brain disorders. Focused ultrasound (FUS) in combination with intravascular microbubbles increases BBB permeability by opening tight junctions, creating endothelial cell openings, improving endocytosis and increasing transcytosis. Here we investigated whether combining FUS and microbubbles with transferrin receptor-targeting liposomes would result in enhanced delivery to the brain of post-natal rats compared with liposomes lacking the BBB-targeting moiety. For all animals, increased BBB permeability was observed after FUS treatment. A 40% increase in accumulation of transferrin receptor-targeting liposomes was observed in the FUS-treated hemisphere, whereas the isotype immunoglobulin G liposomes showed no increased accumulation. Confocal laser scanning microscopy of brain sections revealed that both types of liposomes were mainly observed in endothelial cells in the FUS-treated hemisphere. The results demonstrate that FUS and microbubble treatment combined with BBB-targeting liposomes could be a promising approach to enhance drug delivery to the brain.     

Contrast Agent Kinetics in the Rabbit Brain During Exposure to Therapeutic Ultrasound

Ultrasound-stimulated microbubbles are currently under investigation as a means of transiently disrupting the blood-brain barrier (BBB) and it has been shown that the strength of this effect is highly dependent on ultrasound exposure conditions. The objective of this study was to investigate the potential for contrast agent destruction in the brain under conditions relevant to BBB disruption with a view to determining its possible influence on effective exposure parameters. An ultrasound imaging array was mounted within the aperture of a 1.68-MHz focused therapy transducer. Pulse lengths of 10 ms were used at repetition rates of 0.1–2.0 Hz and pressures from 0.30–0.88 MPa. Contrast imaging was performed after the bolus injection of Definity™, and contrast time-intensity curves were then analyzed for regions-of-interest exposed to the therapy beam. Individual therapy pulses resulted in microbubble destruction, with the degree of agent depletion and replenishment time increasing with transmit pressure. As the pulse repetition rate was increased, agent reperfusion between pulses was incomplete and the concentration within the beam was progressively diminished, to a degree dependent on both pressure and repetition rates. These results demonstrate that microbubble concentration can be substantially influenced by destruction induced by therapeutic ultrasound pulses. The kinetics of this effect may therefore be a significant factor influencing the efficiency of BBB disruption, suggesting that monitoring of the spatial and temporal distribution of contrast agents may be warranted to guide and optimize BBB disruption therapy in both preclinical and clinical contexts. (E-mail: goertz@sri.utoronto.ca)     

Effect of focused ultrasound applied with an ultrasound contrast agent on the tight junctional integrity of the brain microvascular endothelium

Previous studies have investigated a potential method for targeted drug delivery in the central nervous system that uses focused ultrasound bursts combined with an ultrasound contrast agent to temporarily disrupt the blood-brain barrier (BBB). The purpose of this work was to investigate the integrity of the tight junctions (TJs) in rat brain microvessels after this BBB disruption. Ultrasound bursts (1.5-MHz) in combination with a gas contrast agent (Optison) was applied at two locations in the brain in 25 rats to induce BBB disruption. Using immunoelectron microscopy, the distributions of the TJ-specific transmembrane proteins occludin, claudin-1, claudin-5, and of submembranous ZO-1 were examined at 1, 2, 4, 6 and 24 h after sonication. A quantitative evaluation of the protein expression was made by counting the number of immunosignals per micrometer in the junctional clefts. BBB disruption at the sonicated locations was confirmed by the leakage of i.v. administered horseradish peroxidase (HRP, m.w. 40,000 Da) and lanthanum chloride (La(3+), m.w. approximately 139 Da). Leakage of these agents was observed at 1 and 2 h and, in a few vessels, at 4 h after ultrasound application. These changes were paralleled by the apparent disintegration of the TJ complexes, as evidenced by the redistribution and loss of the immunosignals for occludin, claudin-5 and ZO-1. Claudin-1 seemed less involved. At 6 and 24 h after sonication, no HRP or lanthanum leakage was observed and the barrier function of the TJs, as indicated by the localization and density of immunosignals, appeared to be completely restored. This study provides the first direct evidence that ultrasound bursts combined with a gas contrast agent cause disassembling of the TJ molecular structure, leading to loss of the junctional barrier functions in brain microvessels. The BBB disruption appears to last up to 4 h after sonication and permits the paracellular passage of agents with molecular weights up to at least 40 kDa. These promising features can be exploited in the future development of this method that could enable the delivery of drugs, antibodies or genes to targeted locations in the brain.     

新型白蛋白微泡经超声介导破裂促进EGFP基因在Cos-7细胞的表达

目的：根据超声介导白蛋白微泡破裂空化效应可以增加真核细胞膜对大分子(如DNA)通透性的原理，探讨一种新的转基因方法，以便安全有效和定向地转移目的基因。方法：实验中选择绿色荧光蛋白基因EGFP为标记基因，以自制的白蛋白微泡为载体，用超声介导微泡破裂的方法在体外进行Cos—7细胞的基因转化，同时以脂质体为对照，激光共聚焦显微镜和流式细胞计数仪分别定性和定量观察细胞转化效率。锥虫蓝染色观察细胞的活性。结果：体外试验发现0．8MHz、1．0W／cm^2、10％占空比(dutycycle)、60s超声介导10％白蛋白微泡破裂可以有效稳定地转化EGFP基因在Cos—7细胞表达，且对细胞无毒副作用。结论：自制白蛋白微泡是一种安全、有效的新型基因载体，在一定超声条件控制下，能增强基因的转导与表达，有良好的靶向性，提示该技术有应用于临床基因治疗的广阔前景。     

不同超声强度及微泡对基因和组织作用的实验研究

目的探讨不同强度超声破坏微泡对绿色荧光蛋白质粒(green fluorcscent protein，GFP)和小鼠骨骼肌组织的作用。方法分别用0．5w／cm^2、1．0w／cm^2、2．5w／cm^2的超声作用于基因及基因和微泡的混合物2min，琼脂糖凝胶电泳观察质粒基因的电泳图谱变化。并将昆明小白鼠16只分为4组，尾静脉输入白蛋白微泡，同时分别用(0．5w／cm^2、1．0W／cm^2、2．0W／cm^2、2．5w／cm^2的超声作用于小鼠骨骼肌2min．取局部组织HE染色观察超声破坏微泡后组织显微结构的变化。结果不同能量的超声和微泡作用后GFP质粒的电泳图谱结果无变化。0．5w／cm^2超声破坏微泡后无血管充血及红细胞渗出；1．0W／cm^2超声破坏微泡后可引起约30％血管充血，极少量红细胞渗出；2．0W／cm^2超声破坏微泡后可引起约60％血管充血，红细胞渗出较明显；2．5W／cm^2的超声破坏微泡后可使部分骨骼肌变性。结论用1．0W／cm^2和2．0W／cm^2超声作用2min后引起血管充血，红细胞渗出；2．5W／cm^2超声作用2min破坏微泡后可损伤组织。1．0～2．0W／cm^2超声强度破坏微泡后对GFP质粒无明显的损害。