Faculty Opinions recommendation of Microtubules are the only structural constituent of the spindle apparatus required for induction of cell cleavage.

2003 ◽  
Author(s):  
Claire Walczak
Keyword(s):  
Structural Constituent ◽  
Cell Cleavage ◽  
Spindle Apparatus

scholarly journals Microtubules are the only structural constituent of the spindle apparatus required for induction of cell cleavage

2003 ◽  
Vol 162 (3) ◽  
pp. 383-390 ◽  
Author(s):  
G. Bradley Alsop ◽  
Dahong Zhang
Keyword(s):  
Cell Types ◽  
Cell Cortex ◽  
Cleavage Furrow ◽  
Central Spindle ◽  
Structural Constituent ◽  
Cell Cleavage ◽  
Spindle Apparatus

Structural constituents of the spindle apparatus essential for cleavage induction remain undefined. Findings from various cell types using different approaches suggest the importance of all structural constituents, including asters, the central spindle, and chromosomes. In this study, we systematically dissected the role of each constituent in cleavage induction in grasshopper spermatocytes and narrowed the essential one down to bundled microtubules. Using micromanipulation, we produced “cells” containing only asters, a truncated central spindle lacking both asters and chromosomes, or microtubules alone. We show that furrow induction occurs under all circumstances, so long as sufficient microtubules are present. Microtubules, as the only spindle structural constituent, undergo dramatic, stage-specific reorganizations, radiating toward cell cortex in “metaphase,” disassembling in “anaphase,” and bundling into arrays in “telophase.” Furrow induction usually occurs at multisites around microtubule bundles, but only those induced by sustained bundles ingress. We suggest that microtubules, regardless of source, are the only structural constituent of the spindle apparatus essential for cleavage furrow induction.

Structures Formed by Cryoprotective Agents Used in Freezc-Etching

1971 ◽  
Vol 29 ◽  
pp. 448-449
Author(s):  
G. G. Cocks ◽  
C. E. Cluthe
Keyword(s):  
Aqueous Solution ◽  
Polyethylene Oxide ◽  
Liquid Nitrogen Temperature ◽  
Ice Crystals ◽  
Etching Technique ◽  
Structural Constituent ◽  
Cryoprotective Agents ◽  
Quick Freezing ◽  
Freeze Etching ◽  
Fractured Surface

The freeze etching technique is potentially useful for examining dilute solutions or suspensions of macromolecular materials. Quick freezing of aqueous solutions in Freon or propane at or near liquid nitrogen temperature produces relatively large ice crystals and these crystals may damage the structures to be examined. Cryoprotective agents may reduce damage to the specimem, hut their use often results in the formation of a different set of specimem artifacts.In a study of the structure of polyethylene oxide gels glycerol and sucrose were used as cryoprotective agents. The experiments reported here show some of the structures which can appear when these cryoprotective agents are used.Figure 1 shows a fractured surface of a frozen 25% aqueous solution of sucrose. The branches of dendritic ice crystals surrounded hy ice-sucrose eutectic can be seen. When this fractured surface is etched the ice in the dendrites sublimes giving the type of structure shown in Figure 2. The ice-sucrose eutectic etches much more slowly. It is the smooth continuous structural constituent surrounding the branches of the dendrites.

Birefringence and Ultrastructure of Isolated, Stabilized Spindles

1976 ◽  
Vol 34 ◽  
pp. 64-65
Author(s):  
James R. LaFountain ◽  
Robert L. Evans
Keyword(s):  
Fiber Birefringence ◽  
Spindle Apparatus

Previous investigations on the spindle apparatus in primary spermatocytes of the crane fly, Nephrotoma suturalis, with polarizing optics have shown that chromosomal fibers can be detected as positively birefringent bands extending from the chromosomes to the poles (1). Chromosomal fiber birefringence reaches a maximum at metaphase when five distinct fibers can be seen in each half spindle. An obvious question raised by these results was what is the ultrastructural basis of birefringence?Initial attempts to characterize the ultrastructure of crane-fly spindles showed that there were hundreds of microtubules (MTs) in these spindles, but there was no evidence that they were distributed in a pattern that corresponded to the pattern of birefringence (2,3).

Optimization of ultraviolet irradiation of Clarias gariepinus (Burchell, 1822) eggs for androgen production

Zygote ◽  
2021 ◽  
pp. 1-6
Author(s):  
Victor Tosin Okomoda ◽  
Haziqah Jumahat Nursyaza ◽  
Ijabo Oga Samuel ◽  
Anuar Hassan ◽  
Abraham Sunday Oladimeji ◽  
...  
Keyword(s):  
Survival Rate ◽  
Uv Irradiation ◽  
Uv Light ◽  
Clarias Gariepinus ◽  
African Catfish ◽  
Chromosome Counting ◽  
Complete Inactivation ◽  
Cell Cleavage ◽  
Optimal Protocol ◽  
Prolonged Duration

Summary The optimum distance and duration of ultraviolet (UV) irradiation for the complete inactivation of African catfish Clarias gariepinus egg nucleus was investigated in this study. The UV light was suspended above the unfertilized eggs at four distances (5, 10, 20 and 30 cm) and for five durations (1, 2, 3, 4 and 5 min). Then, the irradiated eggs were activated with sperm from diploid C. gariepinus and cold shocked at 5°C for 5 min just moments before cell cleavage. Ploidy analysis was performed using karyotype chromosome counting. The results obtained suggested that the further the distance, the better the hatchability rate, however prolonged duration seemed to significantly reduced hatchability. All treatments with surviving progenies at the end of the study showed evidence of successfully diploid gynogen (2n = 56) induction at different percentages. However, the optimal protocol that gave a moderately high hatchability/survival rate and completely induced gynogens was exposure of the eggs to UV irradiation at 20 cm for 1 min. It was concluded that the distance and duration of UV irradiation affects gynogenetic induction in African catfish C. gariepinus.

scholarly journals Delay of HeLa cell cleavage into interphase using dihydrocytochalasin B: retention of a postmitotic spindle and telophase disc correlates with synchronous cleavage recovery.

1995 ◽  
Vol 131 (1) ◽  
pp. 191-205 ◽  
Author(s):  
S N Martineau ◽  
P R Andreassen ◽  
R L Margolis
Keyword(s):  
Mammalian Cell ◽  
Mitotic Spindle ◽  
Cyclin B ◽  
Cell Cortex ◽  
Cleavage Furrow ◽  
Actin Assembly ◽  
Cell Cleavage ◽  
Integral Structure ◽  
G1 Cells ◽  
Molecular Signals

The molecular signals that determine the position and timing of the cleavage furrow during mammalian cell cytokinesis are presently unknown. We have studied in detail the effect of dihydrocytochalasin B (DCB), a drug that interferes with actin assembly, on specific late mitotic events in synchronous HeLa cells. When cleavage furrow formation is blocked at 10 microM DCB, cells return to interphase by the criteria of reformation of nuclei with lamin borders, degradation of the cyclin B component of p34cdc2 kinase, and loss of mitosis specific MPM-2 antigens. However, the machinery for cell cleavage is retained for up to one hour into G1 when cleavage cannot proceed. The components retained consist prominently of a "postmitotic" spindle and a telophase disc, a structure templated by the mitotic spindle in anaphase that may determine the position and timing of the cleavage furrow. Upon release from DCB block, G1 cells proceed through a rapid and synchronous cleavage. We conclude that the mitotic spindle is not inevitably destroyed at the end of mitosis, but persists as an integral structure with the telophase disc in the absence of cleavage. We also conclude that cell cleavage can occur in G1, and is therefore an event metabolically independent of mitosis. The retained telophase disc may indeed signal the position of furrow formation, as G1 cleavage occurs only in the position where the retained disc underlies the cell cortex. The protocol we describe should now enable development of a model system for the study of mammalian cell cleavage as a synchronous event independent of mitosis.

scholarly journals Uncommon patterns of antinuclear antibodies recognizing mitotic spindle apparatus antigens and clinical associations

Medicine ◽  
2018 ◽  
Vol 97 (34) ◽  
pp. e11727
Author(s):  
Juan Felipe Betancur ◽  
Adriana Londoño ◽  
Victoria Eugenia Estrada ◽  
Sandra Liliana Puerta ◽  
Sandra Marcela Osorno ◽  
...  
Keyword(s):  
Mitotic Spindle ◽  
Antinuclear Antibodies ◽  
Spindle Apparatus ◽  
Clinical Associations

scholarly journals Abnormal Micronuclear Telomeres Lead to an Unusual Cell Cycle Checkpoint and Defects in Tetrahymena Oral Morphogenesis

2008 ◽  
Vol 7 (10) ◽  
pp. 1712-1723 ◽  
Author(s):  
Karen E. Kirk ◽  
Christina Christ ◽  
Jennifer M. McGuire ◽  
Arun G. Paul ◽  
Mithaq Vahedi ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Mitotic Spindle ◽  
Tetrahymena Thermophila ◽  
Germ Line ◽  
Cell Cycle Checkpoint ◽  
Dna Damage Checkpoint ◽  
Telomeric Dna ◽  
Spindle Apparatus ◽  
Cycle Checkpoint

ABSTRACT Telomere mutants have been well studied with respect to telomerase and the role of telomere binding proteins, but they have not been used to explore how a downstream morphogenic event is related to the mutated telomeric DNA. We report that alterations at the telomeres can have profound consequences on organellar morphogenesis. Specifically, a telomerase RNA mutation termed ter1-43AA results in the loss of germ line micronuclear telomeres in the binucleate protozoan Tetrahymena thermophila. These cells also display a micronuclear mitotic arrest, characterized by an extreme delay in anaphase with an elongated, condensed chromatin and a mitotic spindle apparatus. This anaphase defect suggests telomere fusions and consequently a spindle rather than a DNA damage checkpoint. Most surprisingly, these mutants exhibit unique, dramatic defects in the formation of the cell's oral apparatus. We suggest that micronuclear telomere loss leads to a “dynamic pause” in the program of cortical development, which may reveal an unusual cell cycle checkpoint.

Sign in / Sign up

Export Citation Format

Share Document