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

BIOCELL ◽  
2003 ◽  
Vol 27 (3) ◽  
pp. 329-346
Author(s):  
ALBERTO J. SOLARI ◽  
MONICA I. RAHN ◽  
ALICIA SAURA ◽  
HUGO D. LUJAN
Keyword(s):  
Nuclear Envelope ◽  
Giardia Lamblia ◽  
Nuclear Division ◽  
Ventral Disk ◽  
Unique Mechanism

Nuclear division in the marine dinoflagellate Oxyrrhis marina

1986 ◽  
Vol 85 (1) ◽  
pp. 161-175
Author(s):  
X.P. Gao ◽  
J.Y. Li
Keyword(s):  
Nuclear Envelope ◽  
Phylogenetic Relationships ◽  
Nuclear Division ◽  
Metaphase Plate ◽  
Active Role ◽  
Ultrastructural Changes ◽  
Interphase Nuclei ◽  
Oxyrrhis Marina ◽  
Two Stages ◽  
Anaphase B

The nuclear division of Oxyrrhis marina is a very distinct one among the mitoses of dinoflagellates that have been studies. Using synchronized populations, we have investigated the ultrastructural changes in this nuclear division. In interphase, nuclei can be classified into two groups on the basis of the shapes of the chromosomes. Y- and U-shaped chromosomes have been observed in both types of interphase nuclei. By prophase the nucleus becomes oval, many nuclear plaques appear on the nuclear envelope, and many microtubules radiate from these nuclear plaques within the nucleus. Metaphase can be identified by the characteristic arrangement of the chromosomes; an equatorial metaphase plate is absent. As in many higher organisms, anaphase includes two stages: anaphase A and anaphase B. During anaphase A the nucleus does not apparently elongate and the chromosomes migrate towards the poles by a combination of the shortening of the chromosome-associated microtubules and the elongation of those located between daughter chromosomes. During anaphase B the nucleus elongates to about twice its former length. This elongation may result from growth of the interzonal nuclear envelope. Dividing nucleoli are associated with microtubules, which suggests that microtubules may play an active role in the division of the nucleolus. The evolution of mitosis and the phylogenetic relationships between Oxyrrhis, typical dinoflagellates and Syndinium are discussed.

Ultrastructural changes in nuclear membranes and organelle associations during mitosis of the aquatic fungus Entophlyctis sp.

1975 ◽  
Vol 53 (7) ◽  
pp. 627-646 ◽  
Author(s):  
Martha J. Powell
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Nuclear Division ◽  
Ultrastructural Changes ◽  
Aquatic Fungus ◽  
Electron Microscopic ◽  
Mitotic Apparatus ◽  
Inner Membrane ◽  
Nuclear Membranes ◽  
Spindle Microtubules

Electron microscopic observations on an endobiotic chytrid, Entophlyctis sp., have revealed a mitotic apparatus which is presently unique among fungi. Daughter nuclear envelopes are reconstituted from cisternae apparently proliferated by the inner membrane of the nuclear envelope. Before nuclear division, centrioles replicate and migrate to the poles of the nucleus. Large pores appear at this time in a depression of the nuclear envelope opposite the paired centrioles. This region of the envelope fragments and leaves polar fenestrae as spindle microtubules appear in the nucleus. The inner membrane of the nuclear envelope then invaginates and proliferates cisternae until a layer of inner membrane cisternae lines the original nuclear envelope at late metaphase. Connections between the inner membrane of the original nuclear envelope and the cisternae persist until telophase. As the spindle elongates and the inner membrane cisternae fuse centripetally to form a reticulum around the chromatin mass, the original nuclear envelope opens more at the poles. The reticulum becomes the nuclear envelope of the new daughter nuclei. When the original envelope finally disperses, it is distinguishable from the endoplasmic reticulum only by the presence of pores. Microbodies are consistently associated with the original nuclear envelope and appear adjacent to the new daughter envelopes at the end of telophase. Densely staining arms project from the sides of the primary centrioles toward the polar mitochondria.

The ultrastructure of nuclear division in Armillaria mellea: meiosis

1979 ◽  
Vol 57 (18) ◽  
pp. 1860-1872 ◽  
Author(s):  
Diane Cope Peabody ◽  
Jerome J. Motta
Keyword(s):  
Nuclear Envelope ◽  
Membrane Structure ◽  
Nuclear Division ◽  
Spindle Pole ◽  
Armillaria Mellea ◽  
Spindle Pole Bodies ◽  
Late Telophase ◽  
Meiosis I ◽  
Metaphase I

Meiosis I in isolates of Armillaria mellea in which subhymenial hyphae are uninucleate and lack clamp connections was examined ultrastructurally. Although the overall pattern of development and basidiosporogenesis appears similar to other Homobasidiomycetes it was observed that spindle pole bodies are predominantly monoglobular and are associated with a unique membrane structure of the subtending nuclear envelope. The nuclear envelope also disappears at metaphase I and reforms by the coalescence of membrane fragments around the compacted chromatin at late telophase I. The significance of these features in relation to other Basidiomycetes is briefly discussed.

Cell and nucleomorph division in the alga Cryptomonas

1982 ◽  
Vol 60 (11) ◽  
pp. 2440-2452 ◽  
Author(s):  
Lisa McKerracher ◽  
Sarah P. Gibbs
Keyword(s):  
Endoplasmic Reticulum ◽  
Nuclear Envelope ◽  
Outer Membrane ◽  
Basal Body ◽  
Nuclear Division ◽  
Residual Nucleus ◽  
Inner Membrane ◽  
Double Membrane ◽  
Ultrastructural Investigation ◽  
Periplastidal Compartment

An ultrastructural investigation of cell and nuclear division in Cryptomonas sp. (θ) was made with particular emphasis on the mode of division of the chloroplast and nucleomorph. Mitosis is similar to that in other cryptomonads except that the nuclear envelope remains mostly intact. Division of the single chloroplast occurs in preprophase by constriction through the dorsal bridge. Frequently there is a lag between the division of the chloroplast and the division of its envelope of chloroplast endoplasmic reticulum. In addition, the inner membrane of the chloroplast endoplasmic reticulum may infold well in advance of the outer membrane.The nucleomorph is a unique double membrane limited organelle which is found in the periplastidal compartment of cryptomonads. It divides in preprophase following basal body replication but before division of the chloroplast and its chloroplast endoplasmic reticulum is complete. The inner membrane of the nucleomorph envelope invaginates first forming a double membraned baffle. The outer membrane invaginates next and completes division. Microtubules are not involved in nucleomorph division. None were observed and colchicine, which inhibited nuclear division, did not inhibit nucleomorph division. The theory that the nucleomorph is the residual nucleus of a former eukaryotic endosymbiont is reevaluated in light of these new observations.

Presence of a protrusion on the ventral disk of adhered trophozoites of Giardia lamblia

1999 ◽  
Vol 85 (12) ◽  
pp. 951-955 ◽  
Author(s):  
Adriana Lanfredi-Rangel ◽  
José A. Diniz Jr ◽  
Wanderley de Souza
Keyword(s):  
Giardia Lamblia ◽  
Ventral Disk

Giardia lamblia: behavior of the nuclear envelope

2004 ◽  
Vol 94 (4) ◽  
pp. 254-264 ◽  
Author(s):  
Marlene Benchimol
Keyword(s):  
Nuclear Envelope ◽  
Giardia Lamblia

scholarly journals Nek8445, a protein kinase required for microtubule regulation and cytokinesis in Giardia lamblia

2020 ◽  
Vol 31 (15) ◽  
pp. 1611-1622
Author(s):  
Kelly M. Hennessey ◽  
Germain C. M. Alas ◽  
Ilse Rogiers ◽  
Renyu Li ◽  
Ethan A. Merritt ◽  
...  
Keyword(s):  
Cell Division ◽  
Protein Kinase ◽  
Giardia Lamblia ◽  
Cell Shape ◽  
Microtubule Array ◽  
Ventral Disk

Here we study the role of Nek8445 in regulating cell division and microtubule array organization in Giardia. Depletion of Nek8445 results in 87% of cells being stalled or blocked in cytokinesis. Nek8445 regulates ventral disk organization, funis formation, axoneme exit, and cell shape, all of which contribute to the observed cytokinesis defects.

scholarly journals The ultrastructure and timing of events in the nuclear cycle of the fungus Entomophaga aulicae

1988 ◽  
Vol 90 (3) ◽  
pp. 501-516
Author(s):  
FAYE MURRIN ◽  
WILLIAM NEWCOMB ◽  
I. BRENT HEATH
Keyword(s):  
Nuclear Envelope ◽  
Linear Array ◽  
Nuclear Division ◽  
Metaphase Plate ◽  
Serial Sections ◽  
Free Zone ◽  
Nuclear Cycle ◽  
Full Complement ◽  
Spindle Microtubules ◽  
Spindle Elongation

The ultrastructure of the mitotic nuclear division cycle of the fungus Entomophaga aulicae was studied from serial sections of hyphal tips and protoplasts. The extranuclear bar-shaped nucleus- associated organelle (NAO) remained associated with the persistent nuclear envelope throughout. Prior to spindle formation, a patch of intranuclear NAO-associated chromatin detached from the nuclear envelope to yield a chromatin free zone containing fine filaments and a linear array of presumptive kinetochores. Early metaphase spindles less than 1μm in length were characterized by a ‘fused’ metaphase plate consisting of kinetochore-associated chromatin and a full complement of at least 15 kinetochore microtubules per half-spindle, while most of the chromatin was remote from the intranuclear spindle. Analysis of the distribution of antiparallel spindle microtubules indicated that polar separation and concomitant spindle elongation through metaphase were not accompanied by intermicrotubule sliding. Anaphase exhibited extensive decondensation of the large patches of condensed chromatin characteristic of all other stages. In a logarithmically growing protoplast population all nuclei contained spindle microtubules, with metaphase occupying approximately 66% of the nuclear cycle time. The calculated genome size of 4.3 pg, and average DNA content per chromosome of 0.3 pg, are extremely high for fungi.

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