scholarly journals Quantitative studies on the polarization optical properties of living cells II. The role of microtubules in birefringence of the spindle of the sea urchin egg.

1981 ◽  
Vol 89 (1) ◽  
pp. 121-130 ◽  
Author(s):  
Y Hiramoto ◽  
Y Hamaguchi ◽  
Y Shóji ◽  
T E Schroeder ◽  
S Shimoda ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Sea Urchin ◽  
Preceding Paper ◽  
Living Cells ◽  
Mitotic Apparatus ◽  
Form Birefringence ◽  
Quantitative Studies ◽  
Sea Urchin Egg ◽  
Interpolar Distance

Birefringence of the mitotic apparatus (MA) and its change during mitosis in sea urchin eggs were quantitatively determined using the birefringence detection apparatus reported in the preceding paper (Hiramoto el al., 1981, J. Cell Biol. 89:115-120). The birefringence and the form of the MA are represented by five parameters: peak retardation (delta p), through retardation (delta t), interpolar distance (D1), the distance (D2) between chromosome groups moving toward poles, and the distance (D3) between two retardation peaks. Distributions of birefringence retardation and the coefficient of birefringence in the spindle were quantitatively determined in MAs isolated during metaphase and anaphase. The distribution of microtubules (MTs) contained in the spindle is attributable to the form birefringence caused by regularly arranged MTs. The distribution coincided fairly well with the distribution of MTs in isolated MAs determined by electron microscopy. Under the same assumption, the distribution of MTS in the spindle in living cells during mitosis was determined. The results show that the distribution of MTs and the total amount of polymerized tubulin (MTs) in the spindle change during mitosis, suggesting the assembly and disassembly of MTs as well as the dislocation of MTs during mitosis.

scholarly journals ULTRASTRUCTURE AND BIREFRINGENCE OF THE ISOLATED MITOTIC APPARATUS OF MARINE EGGS

1967 ◽  
Vol 34 (3) ◽  
pp. 859-883 ◽  
Author(s):  
Lionel I. Rebhun ◽  
Greta Sander
Keyword(s):  
Electron Microscopy ◽  
Refractive Index ◽  
Sea Urchin ◽  
Major Part ◽  
Living Cells ◽  
Mitotic Apparatus ◽  
Positive Form ◽  
Form Birefringence ◽  
Microscopy Examination ◽  
Intrinsic Birefringence

Isolated mitotic apparatuses (MA) of clam and sea urchin eggs were investigated by polarizing and electron microscopy. Examination of fixed MA in oils of different refractive index revealed that at least 90% of the retardation of isolated MA is due to positive, form birefringence, the remaining retardation deriving from positive, intrinsic birefringence. Electron micrographs reveal the isolated MA to be composed of microtubules, ribosome-like particles, and a variety of vesicles. In the clam MA the number of vesicles and ribosome-like particles relative to the number of microtubules is much lower than in the sea urchin MA. In clam MA this allows form and intrinsic birefringence to be related directly to microtubules. The relation of birefringence to microtubules in isolated sea urchin MA is more complex since ribosome-like particles adhere to microtubules, are oriented by them, and are likely to contribute to the form birefringence of the isolated MA. However, comparison of values of retardation for clam and sea urchin MA, indicates that the major part of the birefringence in sea urchin MA is also due to microtubules. The interpretation of the structures giving rise to birefringence in the MA of the living cells is likely to be even more complex since masking substances, compression, or tension on the living MA may alter the magnitude or sign of the birefringence.

scholarly journals A Quantitative Description of Protoplasmic Movement During Cleavage in the Sea-Urchin Egg

1958 ◽  
Vol 35 (2) ◽  
pp. 407-424
Author(s):  
Y. HIRAMOTO
Keyword(s):  
Cell Division ◽  
Sea Urchin ◽  
Quantitative Description ◽  
Motive Force ◽  
Mitotic Apparatus ◽  
Band Theory ◽  
Cytoplasmic Granules ◽  
Carbon Particles ◽  
Sea Urchin Egg ◽  
Protoplasmic Movement

1. Protoplasmic movements during cleavage in the eggs of the heart-urchin Clypeaster japonicus have been followed by tracing the movements of cytoplasmic granules and of carbon particles adhering to the surface. 2. These movements are quantitatively described in normal eggs and in eggs whose mitotic apparatus has been destroyed by colchicine. 3. The results obtained are qualitatively similar to those obtained by Spek and by Dan and his collaborators. 4. Endoplasmic movement and changes in the length and shape of the astral rays are readily explained by the contracting-ring (band) theory. 5. The location of the motive force of cell division is discussed.

scholarly journals A COMPARATIVE STUDY OF THE ISOLATION OF THE CORTEX AND THE ROLE OF THE CALCIUM-INSOLUBLE PROTEIN IN SEVERAL SPECIES OF SEA URCHIN EGG

1969 ◽  
Vol 41 (1) ◽  
pp. 133-144 ◽  
Author(s):  
R. E. Kane ◽  
R. E. Stephens
Keyword(s):  
Comparative Study ◽  
Sea Urchin ◽  
Protein Composition ◽  
Cortical Region ◽  
Cortical Granules ◽  
Divalent Ions ◽  
Sea Urchin Egg ◽  
Protein Gelation ◽  
Isolated Cortex

A comparative study was made of the isolation of the cortex in the eggs of several sea urchin species. Since the isolation method developed by Sakai depends on the presence of magnesium in the medium, the protein composition of the cortex was investigated to determine whether the protein component of the egg described by Kane and Hersh which is gelled by divalent ions, is present in these cortices. Isolation of the cortex was found to require the same divalent ions at the same concentrations as protein gelation, and in the eggs of some species much of the gel protein of the cell was found in the isolated cortical material. In the eggs of other species a smaller fraction of this protein was found in the isolated cortex, although it was more concentrated there than in the endoplasm, and in one species this protein appeared to be uniformly distributed throughout the cell. These results indicate that this protein is localized in the cortical region of the eggs of some species of sea urchin, possibly in the cortical granules, but also point up the fact that results from one species cannot be uncritically extrapolated to others.

scholarly journals Effects of Dithiothreitol on Fertilization and Early Development in Sea Urchin

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3573
Author(s):  
Nunzia Limatola ◽  
Jong Tai Chun ◽  
Sawsen Cherraben ◽  
Jean-Louis Schmitt ◽  
Jean-Marie Lehn ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Early Development ◽  
Sea Urchin ◽  
Actin Filaments ◽  
Cortical Granule ◽  
Cortical Actin ◽  
Phenotypic Changes ◽  
Sea Urchin Egg ◽  
Cortical Granule Exocytosis

The vitelline layer (VL) of a sea urchin egg is an intricate meshwork of glycoproteins that intimately ensheathes the plasma membrane. During fertilization, the VL plays important roles. Firstly, the receptors for sperm reside on the VL. Secondly, following cortical granule exocytosis, the VL is elevated and transformed into the fertilization envelope (FE), owing to the assembly and crosslinking of the extruded materials. As these two crucial stages involve the VL, its alteration was expected to affect the fertilization process. In the present study, we addressed this question by mildly treating the eggs with a reducing agent, dithiothreitol (DTT). A brief pretreatment with DTT resulted in partial disruption of the VL, as judged by electron microscopy and by a novel fluorescent polyamine probe that selectively labelled the VL. The DTT-pretreated eggs did not elevate the FE but were mostly monospermic at fertilization. These eggs also manifested certain anomalies at fertilization: (i) compromised Ca2+ signaling, (ii) blocked translocation of cortical actin filaments, and (iii) impaired cleavage. Some of these phenotypic changes were reversed by restoring the DTT-exposed eggs in normal seawater prior to fertilization. Our findings suggest that the FE is not the decisive factor preventing polyspermy and that the integrity of the VL is nonetheless crucial to the egg’s fertilization response.

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