Chávez-Munguía Bibiana, Tsutsumi Víctor, Martínez-Palomo Adolfo
Departamento de Patología Experimental, Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico.
Exp Parasitol. 2006 Nov;114(3):235-9. doi: 10.1016/j.exppara.2006.03.005. Epub 2006 Apr 24.
We have analyzed by transmission electron microscopy the mitotic process of Entamoeba histolytica trophozoites in an asynchronous population of axenically cultured parasites. Our observations showed that nuclear microtubules, initially located at random in the karyosome during prophase, formed in subsequent stages a mitotic spindle closely related to the nuclear membrane at the polar regions of dividing nuclei. In late prophase and in anaphase, chromosomes appeared as dense bodies 0.1-0.5 microm. At least 15 chromosomes appeared in favorable planes of section, arranged as an incomplete elliptical circle, in close contact with microtubules. There was no morphological evidence of structures resembling the kinetochores of higher eukaryotes. When cut in cross-section, the mitotic spindle was made of 28-35 microtubular rosette assemblies. The latter probably correspond to a similar number of chromosomes, as has been shown by others with pulse-field electrophoresis and fluorescence microscopy of trophozoite spreads. In turn, each microtubular rosette was constituted by 7-12 parallel microtubules. In later stages of the metaphase, two sets of chromosomes were disposed forming a pair of elliptical circles. An additional finding in the dividing nuclei of E. histolytica trophozoites was the presence of compact conglomerates of numerous particles 50 nm in diameter, of similar electron density, shape, and size, probably corresponding to RNA episomes.
我们通过透射电子显微镜分析了在无菌培养的寄生虫异步群体中溶组织内阿米巴滋养体的有丝分裂过程。我们的观察结果表明，核微管在前期最初随机分布在核小体中，在随后的阶段形成了一个有丝分裂纺锤体，该纺锤体在分裂核的极区与核膜紧密相关。在前期后期和后期，染色体呈现为直径0.1 - 0.5微米的致密体。在有利的切片平面上至少出现了15条染色体，排列成一个不完整的椭圆，与微管紧密接触。没有形态学证据表明存在类似于高等真核生物动粒的结构。当横切时，有丝分裂纺锤体由28 - 35个微管玫瑰花结组装体组成。正如其他人通过脉冲场电泳和滋养体铺展的荧光显微镜所显示的那样，后者可能对应于相似数量的染色体。反过来，每个微管玫瑰花结由7 - 12条平行微管组成。在中期后期，两组染色体排列形成一对椭圆。在溶组织内阿米巴滋养体的分裂核中的另一个发现是存在许多直径为50纳米的致密聚集体，它们具有相似的电子密度、形状和大小，可能对应于RNA附加体。
