Is the Dog a Useful Model for Accelerated Calcification Study of Cardiovascular Bioprostheses?

Abstract: Chitosan posttreatment has been shown to be effective in prevention of calcification of the glutaral-dehyde treated bovine pericardium when implanted sub-dermally in rats for 12 weeks. The efficacy of chitosan posttreatment in complete calcium mitigation of the glutaraldehyde treated porcine aortic valves implanted in the right side of the heart in dogs was well-documented in our previous study. In this study, an attempt has been made to evaluate the merit of the chitosan posttreatment in prevention of calcification of the glutaraldehyde (GA) treated porcine aortic valved conduits in the systemic circulation in dogs for a period of 5 months. Eleven mongrel dogs underwent left thoracotomy. Porcine aortic valved conduits treated with 0.625% GA (n = 5) and GA-chitosan (n = 6) were implanted in the descending thoracic aortas of the dogs for 5 months. Gross histological observations showed no calcification in either the 0.625% GA treated or in the GA-chitosan treated valved conduits at 5 months. This was confirmed by results of quantitative analyses for calcium in each explant. There was no significant difference in calcium content between the GA only (Ca, 0.43 ± 0.26 mg/g) and GA-chitosan treated (Ca, 0.51 ± 0.19 mg/g; p = 0.5959) valved conduits. This study suggests that the dog is not a suitable model for evaluating the efficacy of a calcium mitigating agent in bioprostheses implanted in systemic circulation.     

Cadaver preservation and dissection

Summary Postgraduate cadaver dissection is an unsurpassed method of maintaining and improving one's knowledge of anatomy. Since fresh cadavers are not always available, some form of preservation is often required especially for courses or workshops. A technique using glutaraldehyde is described and its pros and cons compared with the time honored formaldehyde-phenol technique. The method is particularly suitable for cadaver preservation for up to 6 weeks and the treated tissues remain unstained and retain a life-like texture. Such cadavers are ideal for short surgical dissection workshops.     

环氧氯丙烷对戊二醛鞣制的猪主动脉瓣防钙化化学改性的实验研究

目的探索对戊二醛鞣制猪主动脉瓣改性的新的防钙化处理方法,延长生物瓣使用寿命。方法用环氧氯丙烷对戊二醛鞣制的猪主动脉瓣进行改性处理,新鲜瓣膜组作为空白组,戊二醛处理组作为对照组。将三组猪主动脉瓣埋植于大鼠皮下,分别于2、4、8周后取出,通过原子吸收光谱法测定猪主动脉瓣钙含量和VonKossa钙染色,以评价环氧氯丙烷化学改性对戊二醛鞣制的猪主动脉瓣钙化的影响。结果光镜下显示环氧氯丙烷改性处理组较少炎性细胞浸润,胶原纤维结构保持良好;戊二醛组试片,则有大片状钙盐沉积及较多炎性细胞浸润,胶原纤维结构破坏严重;SD大鼠皮下包埋实验各组瓣膜的钙化程度在第2、4、8周时逐渐增加,在第4、8周时实验组明显低于对照、空白组(P<0.05)。说明环氧氯丙烷对戊二醛鞣制的猪主动脉瓣改性处理,可显著延缓猪主动脉瓣的钙化进程。Von Kossa染色也显示环氧氯丙烷改性处理明显减轻了戊二醛鞣质的生物瓣膜的钙化。结论通过环氧氯丙烷对猪主动脉生物瓣进行进一步的化学改性处理,可显著延缓猪主动脉生物瓣的钙化进程,可望成为一种防止猪主动脉生物瓣钙化和坏死及其功能衰退的有效方法。     

The benzene metabolite trans,trans-muconaldehyde blocks gap junction intercellular communication by cross-linking connexin43

Benzene is used at large volumes in many different human activities. Hematotoxicity and cancer-causation as a result of benzene exposure was recognized many years ago, but the mechanisms involved remain unclear. Aberrant regulation of gap junction intercellular communication (GJIC) has been linked to both cancer induction and interference with normal hematopoietic development. We have previously suggested that inhibition of GJIC may play a role in benzene toxicity since benzene metabolites were found to block GJIC, the ring-opened trans,trans-muconaldehyde (MUC) being the most potent metabolite. In the present work we have studied the molecular mechanisms underlying the MUC-induced inhibition of gap junctional communication. We show that MUC induces cross-linking of the gap junction protein connexin43 and that this is likely to be responsible for the induced inhibition of GJIC, as well as the loss of connexin43 observed in Western blots. We also show that glutaraldehyde possesses similar effects as MUC, and we compare the effects to that of formaldehyde. The fact that glutaraldehyde and formaldehyde have been associated with induction of leukemia as well as disturbance of hematopoiesis, strengthens the possible link between the effect of MUC on gap junctions, and the toxic effects of benzene.     

戊二醛消毒灭菌性能与腐蚀性的试验观察

目的了解戊二醛消毒剂的消毒灭菌性能及腐蚀性。方法采用悬液定量杀菌、载体浸泡灭菌、医疗器械模拟现场、连续使用稳定性试验、金属腐蚀性试验进行观察。结果含20g/L的戊二醛溶液对枯草杆菌黑色变种芽孢作用30min,杀灭对数值5.00,作用5h对污染在止血钳上的枯草杆菌黑色变种芽孢可达到完全杀灭。含20g/L戊二醛的消毒剂对止血钳、镊子、剪刀浸泡连续使用14d,作用30min对枯草杆菌黑色变种芽孢杀灭对数值3.00。含20g/L的戊二醛消毒剂浸泡72h,对不锈钢、碳钢、铜、铝基本无腐蚀。结论戊二醛消毒剂对细菌芽孢杀灭效果较好,是一种高效消毒剂,同时也可作为灭菌剂;腐蚀性相对较低。     

呼吸机通气管道消毒方法分析

目的研究消毒呼吸机通气管道的最佳方法。方法对比戊二醛、甲醛和洗必泰3种方法的消毒效果。结果消毒60 min时,3种方法均达到标准,但戊二醛的消毒效果与甲醛、洗必泰相比差异有显著意义(P<0.05),消毒90 min,3种消毒效果无差异,但洗必泰对呼吸机通气管道有腐蚀,甲醛有难闻的气味。结论戊二醛与95%乙醇配合消毒迅速彻底,消毒效果优于甲醛和洗必泰。     

Relationship Between Mechanical and Hydrodynamic Properties of Bioprosthesis Produced from Canine Aortic Valve

Static tensile, stress relaxation, and hydrodynamic tests were carried out to investigate the relationships between the mechanical deformation or stiffness of heart valve leaflets and the opening behavior of bioprosthetic valves. The specimens used were fresh and glutaraldehyde (GA)-treated canine aortic valves. The tensile strength depended on the fiber orientation in the leaflet. The deformability of fresh and 0.05% GA-treated tissues was significantly larger than that induced by 0.1-5.0% GA concentrations according to the stress-strain curves. The stress relaxation function, which expresses the viscoelastic property, did not show significant differences in the 0.05-5.0% range of GA concentrations. In the hydrodynamic tests, the opening resistance of fresh and 0.05% GA-treated valves was less than that of 0.1-5.0% GA-treated valves. Thus, it was shown that the hydrodynamic valve functions were closely related to the material properties of aortic valve leaflets.