Form-maintaining factors of the trypomastigote of Trypanosoma cruzi

克氏锥虫的锥乳虫具有多种功能，可在哺乳动物体液中生存。其中一个功能是迅速侵入宿主细胞，如肌肉细胞，这使得锥虫有可能避免宿主的攻击。另一方面，锥乳虫需要被昆虫（一种接吻虫）吮吸来维持物种，这需要它们在血液中停留很长时间。我们发现，在pH值较低的MEM培养基中添加1%牛血清白蛋白（BSA），可以加速色马鞭毛虫向无马鞭毛虫的转化。利用这种培养体系，我们试图寻找维持锥马鞭毛虫形态的因素。首先通过电镜观察其形态变化，证实加速转化是生理反应而非变性反应。对鞭毛旁蛋白的小鼠抗血清进行免疫印迹，再次证实了从密集乳糜虫到无尾虫的转化。在没有牛血清蛋白的情况下，在中性pH和低pH条件下，密乳线虫都不能存活。以前我们认为牛血清白蛋白的作用是中和自溶的乳线虫释放的物质，但它似乎是通过与某些表面成分结合来稳定膜结构。除牛血清白蛋白外，几种血清成分对乳乳突虫无明显的抑制作用，但我们不能确定哪一种对乳乳突虫形态维持最有效。在转化过程中，除了鞭毛旁蛋白外，还丢失了一些蛋白质成分，其中一种是反式唾液酸酶。然而，目前维持锥马鞭毛虫的成分是什么仍有待解决。

Trypomastigotes of Trypanosoma cruzi developed various functions, by which they can survive in body fluid of mammals. One of the functions is the prompt invasion in host cells such as muscle cells which make trypomastigotes possible to avoid the attack from the host. On the other hand trypomastigotes need to be sucked by an insect ( a kissing bug ) to maintain the species, which require them to stay long in the bloodstream. We found that lowered pH of the MEM medium supplemented 1% bovine serum albumin ( BSA ) accelerated the transformation of the trypomastigote to the amastigote. Using this culture system we have tried to look for the factors that maintain the form of the trypomastigote. First of all we observed the morphological change by electronmicroscopy and confirmed that the accelerated transformation was a physiological reaction but not a denaturation reaction. The immunoblotting using a mouse antiserum to the paraflagellar protein reconfirmed the transformation from trypomastigotes to amastigotes. Trypomastigotes can not survive in the neutral pH medium as well as in the low pH in the absence of BSA. Previously we thought that the effect of BSA was to neutralize the released substances from trypomastigotes which lyse themselves, but it seems to be to stabilize the membrane structure by binding to some surface component. Several serum components ban blind to trypomastigotes besides BSA, but we could not determine which was the most effective for the form maintenance of the trypomastigote. Some protein components of the trypomastigote besides the paraflagellar protein were lost during transformation, one of them was trans-sialidase. At present, however, what is the component maintaining the trypomastigote remains to be solved.