Ureña F
Facultad de Medicina, Universidad de Costa Rica.
Rev Biol Trop. 1988 Jun;36(1):129-37.
The ultrastructure of mitotic nuclei of the promastigote Leishmania mexicana ssp. was studied by serial thin sections and three-dimensional reconstructions of each divisional stage. At the beginning of nuclear division (equatorial stage), a set of six dense plaques located about the equatorial region of the nucleus and a microtubular spindle develops in the two opposing poles of the nucleus (two sets of polar microtubules). The microtubular mitotic spindle is entirely intranuclear with the nuclear membrane persisting through mitosis. The polar spindle consists of a discrete bundle of about 50 microtubules and the equatorial spindle is formed by about 100 microtubules. The spindle may contain several continuous microtubules, but no microtubular organizing centres were observed in association with the spindle. The plaques and hemiplaques are associated with microtubular bundles; some of the spindle microtubules converge on kinetochore-like plaques. It is suggested that the spindle has a special significance in the physiology of mitosis. The two sets of hemiplaques may guide the separation of the daughter genomes. At the beginning of the elongational stage the mitotic plaques split into halves and each set of half-plaques migrates to one pole. It is concluded that the dense plaques play a kinetochore-like role and thus Leishmania mexicana ssp. may have six chromosomal units. Mitotic events of this species are essentially similar to those of Trypanosoma cruzi.
通过连续超薄切片和对每个分裂阶段的三维重建，研究了墨西哥利什曼原虫前鞭毛体有丝分裂细胞核的超微结构。在核分裂开始时（赤道期），一组六个致密斑位于细胞核的赤道区域周围，并且在细胞核的两个相对极中形成微管纺锤体（两组极微管）。微管有丝分裂纺锤体完全位于核内，核膜在有丝分裂过程中持续存在。极纺锤体由大约50根微管的离散束组成，赤道纺锤体由大约100根微管形成。纺锤体可能包含几根连续的微管，但未观察到与纺锤体相关的微管组织中心。这些斑和半斑与微管束相关；一些纺锤体微管汇聚在动粒样斑上。有人认为纺锤体在有丝分裂生理学中具有特殊意义。两组半斑可能指导子基因组的分离。在伸长阶段开始时，有丝分裂斑分裂成两半，每组半斑迁移到一个极。得出的结论是，致密斑起到类似动粒的作用，因此墨西哥利什曼原虫可能有六个染色体单位。该物种的有丝分裂事件与克氏锥虫的基本相似。
