The Study on the Virulence of Trypanosoma cruzi

虽然克氏锥虫锥鞭毛体转化为无鞭毛体的过程似乎是自发发生的，但证明了通过将锥鞭毛体保持在由10 mM柠檬酸盐-磷酸盐缓冲液调节的低pH下来加速该过程。这一过程需要一定的营养物质，并涉及化学物质的分离，这些化学物质甚至可以溶解寄生虫。在低pH（4.5-6.0）、添加1%牛白蛋白的组织培养基中，转化迅速完成。用10 mM醋酸盐缓冲液调节的低pH值对寄生虫具有高毒性。有趣的是，高毒力的克隆或菌株的裂解作用比低毒力的强得多。溶素的特性表明，它可能是lipid.The存在下的培养基中的血清在pH 7.4抑制转化，导致在长期维持的锥鞭毛体阶段。比较不同酶切后的动基体小环DNA，发现高毒力克隆或菌株的EcoR Ⅰ酶切DNA片段与低毒力克隆或菌株的EcoR Ⅰ酶切DNA片段有很大的差异，而低毒力克隆或菌株的EcoR Ⅰ酶切DNA片段的模式与高毒力克隆或菌株相同。使用从不同片段获得的探针进行杂交试验，证明存在高病毒性克隆的特异性序列。

Although the process of transformation of Trypanosoma cruzi trypomastigote to amastigote seemed to take place spontaneously, it was demonstrated that the process was accelerated by keeping trypomastigotes at low pH that was adjusted by 10 mM citrate-phosphate buffer. The process required certain nutrients and involved the separation of chemical substances which lysed even parasites. The lytic effect was neutralized by bovine albumin, accordingly the transformation was rapidly completed in tissue culture medium at low pH, 4.5-6.0, supplemented with 1% bovine albumin. Low pH adjusted by 10 mM acetate buffer was highly toxic to parasites. The interesting point is that the lytic effect was much stronger in high-virulent clone or strains than in low virulenct. Characterization of the lysin suggested that it might be lipid.The presence of serum in media at pH 7.4 suppressed the transformation, resulting in the long maintenance of the trypomastigote stage. Bovine albumin cloud replace whole serum but the ability to maintain the trypomastigote was less. Comparison of minicircle DNA of the kinetoplast after digestion by various restricted enzymes revealed that the pattern of DNA fragments digested by EcoRl in the high-virulent clone or strains was very distinct from the low-virulent clone or strains, which shared the same pattern. Hybridization test using the probe obtained from the distinct fragment demonstrated presence of the specific sequence to the high-vireulent clone.