肝移植术后胆管铸型的电镜观察

目的 探讨肝移植术后胆管铸型的超微结构及其与胆道感染的关系.方法 手术过程中,无菌条件下收集11例肝移植术后患者的胆管铸型,留取标本.从留取的标本中随机抽取6例进行扫描电镜观察.结果 6例铸型表现为多种形态,在铸型中均未观察到有细菌或细菌残骸存在.结论 铸型中没有找到细菌的踪迹,胆管炎症可能不是其病因之一.     

TCDD对SD大鼠肝脏超微结构的影响

采用一次性腹腔注射的方法对雌性SD大鼠进行TCDD染毒,剂量为10μg/kg,用透射电镜观察其肝脏超微结构的变化。结果可见,肝细胞部分线粒体溶解,粗面内质网脱颗粒,池崩解,滑面内质网池扩张、融合,侧重以核染色质溶解、部分凝固为特征,肝细胞脂肪变,枯否氏细胞核染色质凝聚,细胞器轻度溶解。提示TCDD染毒24h对大鼠肝脏损害广泛,能使肝细胞和枯否氏细胞超微结构发生明显改变。     

Purine and Its Analogues and Radiation Damage in Bacillus Megaterium Spores

Summary

As an extension of results obtained from radiation studies on caffeine both in other laboratories and more recently in this laboratory using the bacterial spore as the test system, six compounds with chemical structures closely resembling that of caffeine were tested as radiation modifiers. Of these compounds, purine, adenine and hypoxanthine resembled caffeine in sensitizing spores to radiation, while theobromine, xanthine and theophylline did not. These responses are discussed in relation to the electron sequestration hypothesis of cellular sensitization to high-energy radiation.     

Cytotoxic effects and specific gene expression alterations induced by I-125-labeled triplex-forming oligonucleotides

Abstract

Purpose: Triplex-forming oligonucleotides (TFO) bind to the DNA double helix in a sequence-specific manner. Therefore, TFO seem to be a suitable carrier for Auger electron emitters to damage exclusively targeted DNA sequences, e.g., in tumor cells. We studied the influence of I-125 labeled TFO with regard to cell survival and induction of DNA double-strand breaks (DSB) using TFO with different genomic targets and target numbers. Furthermore, the ability of TFO to alter the gene expression of targeted genes was examined.

Materials and methods: TFO were labeled with I-125 using the primer extension method. DNA triplex formation and sequence-specific DSB were demonstrated in vitro. Cell survival was analyzed by colony-forming assay and DNA damage was assessed by microscopic quantification of protein 53 binding protein 1 (53BP1) foci in the human squamous carcinoma cell line II (SCL-II). Quantitative real-time polymerase-chain-reaction (qRT-PCR) was performed to analyze gene expression alterations.

Results: The sequence-specific induction of a single DSB in a 1695 bp long DNA double stranded fragment was demonstrated in vitro. I-125-labeled TFO binding to single and multiple targets were shown to induce a pronounced decrease in cell survival and an increase of DSB. TFO targeting multiple sites differing in the total target number showed a significant different cell killing per decay that is also in good accordance with the observed induction of DSB. Single gene targeting I-125-labeled TFO significantly decreased cell survival and altered gene expression in the targeted gene.

Conclusions: I-125-labeled TFO enable specific targeting of DNA in vitro as well as in a cellular environment and thus induce sequence-specific complex DNA lesions. Therefore I-125-labeled TFO might be a very useful tool for basic DNA repair research.     

Fast Monte Carlo simulation of DNA damage induction by Auger-electron emission

Abstract

Purpose: A local damage model (LDM) was developed to estimate the biological efficiency of Auger-electron-emitting radionuclides.

Materials and methods: The LDM required information on the local dose distribution, local energy spectrum, and clustered DNA damage yields in the cell nucleus. To apply the model, the nucleus was divided into concentric shells where each shell contributed its own local dose, energy spectrum, and damage yield. The local doses and energy spectra were computed using the PENELOPE (PENetration and Energy LOss of Positrons and Electrons) code. The DNA damage yields were estimated using the MCDS (Monte Carlo damage simulation) code.

Results: For a typical 4-μm radius mammalian cell nucleus, the absorbed doses to the cell nucleus per unit cumulated activity, equal to 0.0065, 0.00418, 0.0028, 0.0027 and 0.0015 Gy Bq^?1 s^?1 for ¹²⁵I, ¹¹⁹Sb, ¹²³I, ¹¹¹In and ^99mTc, were within 6% difference with the MIRD (Medical Internal Radiation Dose) published data. The simulated total (simple and complex) single-strand break (SSB) and double-strand break (DSB) yields were in the same order, i.e., ¹²⁵I > ¹¹⁹Sb > ¹²³I > ¹¹¹In > ^99mTc. The agreement between present results and literature data for the DNA damage yields was generally good. More than 75% of the total SSB and DSB yields were contributed from regions within 2.5 μm of the nucleus center.

Conclusions: The proposed methodology was computationally efficient and could be applied to other irradiation geometries such as cell clusters.     

Method for assessing X-ray-induced hydroxyl radical-scavenging activity of biological compounds/materials

A method for correctly assessing hydroxyl radical scavenging activity of antioxidative chemicals and/or biological compounds/materials was proposed. This method can simultaneously assess two factors, i.e. hydroxyl radical-scavenging and 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide (hydroxyl radical adduct of 5,5-dimethyl-1-pyrroline-N-oxide)-reducing ability, as antioxidative properties. In this paper, some biologically common hydrophilic molecules, cell culture media, and rat plasma were tested. X-ray-induced hydroxyl radical can be detected using the electron paramagnetic resonance spin trapping technique. Using X-ray irradiation of the reaction mixture as the hydroxyl radical source, the true hydroxyl radical-scavenging ability of the subjected antioxidant can be assessed. In addition, the method simultaneously measures the reduction of 5,5-dimethyl-2-hydroxy-1-pyrrolidine-N-oxide, to estimate the reducing ability of the antioxidant. Biological materials, such as sugars and proteins, could abolish hydroxyl radical at the biological concentration. Ascorbic acid showed reducing ability at the biological concentration. The simultaneous assessment of hydroxyl radical-scavenging and reducing ability of antioxidants can be an informative index for antioxidants.     

Characteristic alterations of the peritoneum after carbon dioxide pneumoperitoneum

Objective: Any route of entry into the abdomen contributes to alterations of the intraperitoneal organs with different clinical consequences. Characteristic alterations of the peritoneum after CO₂ pneumoperitoneum used in laparoscopic surgery is examined. Methods: A CO₂ pneumoperitoneum with an intraperitoneal pressure of 6 mmHg was applied for 30 min in 32 nude mice. In the course of 4 days, the animals were killed and the peritoneal surface of the abdominal wall was studied by means of scanning electron microscopy. Results: Already 2 h after release of the pneumoperitoneum, mesothelial cells were bulging up. The intercellular clefts thereby increased in size, and the underlying basal lamina became visible. This reaction peaked after 12 h. Subsequently, peritoneal macrophages and lymphocytes filled all gaps, thereby recovering the basal lamina. Conclusion: The morphologic integrity of the peritoneum is temporarily disturbed by a CO₂ pneumoperitoneum. Received: 9 March 1998/Accepted: 24 July 1998     

CO_2激光镫骨足板造孔术后内耳超微结构的实验研究

目的　探讨以CO2 激光行镫骨足板手术对内耳感受器超微结构的影响。方法　 9只白色红目豚鼠分 3组 ,每组 3只 ,分别以功率 2、4、6W的CO2 激光对左耳进行内耳镫骨足板造孔 ,以右耳为对照。术后动物断头处死 ,利用扫描电镜技术观察激光照射对内耳感受器毛细胞的影响。结果　以功率 2W的CO2 激光行内耳镫骨足板造孔术时 ,豚鼠内耳毛细胞未见损伤 ;功率 4W时 ,外毛细胞之间出现云雾状渗出物 ,并有散在的外毛细胞倒伏 ,内毛细胞部分融合 ,表面有球状物附着 ;功率 6W时 ,内耳毛细胞及壶腹嵴毛细胞均被损伤 ,并出现外毛细胞严重缺失、破坏 ,壶腹嵴纤毛广泛损伤、脱落 ,失去原有的形态。结论　应用CO2 激光行镫骨足板手术应注意功率的选择 ,以免造成内耳感受器的损伤。所得实验数据可供激光治疗耳硬化症选择适当的功率参考。     

猪油与豆油对家兔主动脉形态学改变的影响

本实验观察了猪油与豆油对家兔血脂水平和主动脉形态学改变的影响。24只成年家兔分为4组:对照组、高猪油组、低猪油组和豆油组,饲养2个月。结果表明,在普通饲料中加入食用油后,实验动物血清胆固醇升高,并伴有不同程度的主动脉病变。病变为肉眼可见的脂斑和扫描电镜下的鹅卵石样结构,在高猪油组最重,低猪油组最轻。由此可见,过量摄入食用油,即使其主要含不饱和脂肪酸,仍可造成主动脉损伤;而适量摄入猪油,则可能并不产生明显损伤。     

激素对股骨头微血管及组织细胞的影响

目的通过建立激素性股骨头缺血性坏死动物模型,研究股骨头微血管密度(microvas-culardensity,MVD)和股骨头组织细胞超微结构的变化,探讨长期大剂量使用糖皮质激素引起股骨头缺血性坏死的机制。方法健康日本白兔40只,1.86～2.21kg,平均2.06kg。随机分为两组,实验组31只,对照组9只。实验组每周皮下注射醋酸氢化泼尼松8mg/kg,对照组每周皮下注射生理盐水0.32ml/kg。在实验的第4、8和12周分别对实验组和对照组的股骨头行微血管墨汁灌注,研究股骨头MVD的变化;制作半薄切片,在透射电镜下分别观察实验组和对照组的股骨头组织细胞的超微结构。拍摄兔耳背微血管网观察用药前后的变化。结果实验组双侧股骨头松质骨和密质骨的单位面积内MVD与对照组相比在用药3个月后明显下降(P<0.01)。兔耳背微血管网随用药时间的延长逐渐变稀疏。股骨头各系组织细胞内均发现有脂质堆积;骨细胞核膜失去连续性、碎裂,染色质溶解;血管内皮细胞内出现脂滴,胞膜结构不完整,可见明显的裂隙,线粒体肿胀、变圆,结构不清;脂肪细胞异常肥大,核内出现脂滴,并压迫小静脉,管腔变窄;小静脉内可见红细胞相互重叠呈“缗线状”。结论骨内压升高是激素性骨坏死病理过程中的一个表现,与肥大的脂肪细胞压迫小静脉有关。长期大剂量使用糖皮质激素可抑制