Open Access

ARTICLE

A unique mechanism of nuclear division in Giardia lamblia involves components of the ventral disk and the nuclear envelope

by ALBERTO J. SOLARI*, MONICA I. RAHN*, ALICIA SAURA**, HUGO D. LUJAN**

* Centro de Investigaciones en Reproduccion, Facultad de Medicina, UBA, Buenos Aires, Argentina.
** Catedra de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Nacional de Córdoba, Córdoba, Argentina
Address correspondence to: Dr. Alberto Solari. CIR, Facultad de Medicina, Paraguay 2155, (1121) Buenos Aires, ARGENTINA. Fax/Phone: (54-11) 4961 2763; E-mail: asolari@.fmed.uba.ar

BIOCELL 2003, 27(3), 329-346. https://doi.org/10.32604/biocell.2003.27.329

Abstract

The fine structure of the binucleate, parasitic protist Giardia lamblia during interphase and divisional stages was studied by serial thin sectioning and three-dimensional reconstructions. The earlier sign of nuclear division is the development of a few peripheral areas of densely packed chromatin directly attached to the inner nuclear envelope. An intracytoplasmic sheet of ventral disk components grows from the cell periphery towards one of the nuclei, apparently constricting this nucleus, which becomes located at a ventral bulge. After the basal bodies become duplicated, a full nuclear division occurs in trophozoites, giving two pairs of parent-daughter nuclei. This full division occurs in a dorsal-ventral direction, with the resulting nuclear pairs located at the sides of the two sets of basal bodies. A new ventral disk is formed from the diskderived sheets in the cell harboring the four nuclei. Cytokinesis is polymorphic, but at early stages is dorsalto-dorsal. Encysting trophozoites show the development of Golgi cisternae stacks and dense, specific secretory granules. 3-D reconstructions show that cysts contain a single pair of incompletely strangled nuclei. The dividing Giardia lacks a typical, microtubular spindle either inside or outside the nuclei. The nuclear envelope seems to be the only structure involved in the final division of the parent-daughter nuclei.

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