Surface Characters of Dividing Cells

1958 ◽  
Vol 35 (2) ◽  
pp. 396-399
Author(s):  
SHOZO ISHIZAKA
Keyword(s):  
Sea Urchin ◽  
Optical Section ◽  
Camera Lucida ◽  
Centre Of Gravity ◽  
Whole Process ◽  
Spindle Axis ◽  
Sea Urchin Egg ◽  
Dividing Cells

1. The surface movements during division have been studied by marking the naked surface of the sea-urchin egg with charcoal particles. 2. The contours of the largest optical section, the positions of the particles thereon and the positions of the astral centres are recorded in a series of camera lucida drawings. 3. The drawings are then superimposed, the centre of gravity and spindle axis being used for reference. 4. It is thereby shown that there are two surface rings which remain in the same positions throughout the whole process of division. 5. It is concluded that these rings indicate regions where stresses remain balanced during division.

Surface Characters of Dividing Cells

1966 ◽  
Vol 44 (2) ◽  
pp. 225-232
Author(s):  
SHOZO ISHIZAKA
Keyword(s):  
Sea Urchin ◽  
Surface Stress ◽  
Radius Of Curvature ◽  
Surface Movement ◽  
Daughter Cells ◽  
Sea Urchin Egg ◽  
Area Increase ◽  
Dividing Cells ◽  
Division Process ◽  
Surface Area Increase

1. Surface movement of the dividing spermatocyte of the grasshopper, Acrida lata, was followed by a marking method. 2. Throughout the division process of the spermatocytes, incipient daughter cells maintain spherical contours. 3. By direct observation of markers and calculation using the condition given in item 2, the following points are established. (a) As in the sea-urchin egg, there are a pair of circular zones on a grasshopper spermatocyte surface which retain their respective radii unchanged while the cell undergoes a division. (b) In the grasshopper spermatocyte, unlike the sea-urchin egg, the surfaces of these circular zones do change their positions and move towards the poles during division. (c) As a spherical cell goes through a constricted form to become two daughter cells, not only is the radius of curvature of the surface everywhere uniform (item 2), but both axial length and surface area increase uniformly everywhere except in the region of the furrow. 4. From the findings of item 3 it is inferred that the prevailing surface stress is uniform and isotropic, like surface tension, and that the force causing division must be derived from some other parts of the cell such as the furrow cortex or the endoplasm. 5. Basically, the nature of the surface of sea-urchin eggs is similar to that of the spermatocyte. That the circular zones of the former are stationary while those of the latter move steadily during cleavage is tentatively explained in terms of the speed of advance of the furrow in relation to the relaxation time of the cortex.

scholarly journals THE MITOTIC APPARATUS

1962 ◽  
Vol 15 (2) ◽  
pp. 279-287 ◽  
Author(s):  
R. E. Kane
Keyword(s):  
Fine Structure ◽  
Granular Material ◽  
Sea Urchin ◽  
Osmium Tetroxide ◽  
Mitotic Apparatus ◽  
Isolation Medium ◽  
Sea Urchin Egg ◽  
Dividing Cells

The fine structure of the mitotic apparatus isolated from the sea urchin egg has been investigated. The isolation was accomplished by lysis of metaphase eggs in a 1 M solution of hexanediol, buffered at pH 6. The fine structure of the isolated apparatus was studied after fixation with osmium tetroxide directly in the isolation medium. The spindle is composed of fine fibrils, approximately 20 mµ in diameter, which appear tubular. Similar fibrils, radially oriented, are found in the aster. If the isolated mitotic apparatus is exposed to water at pH 6 before fixation, the structure is considerably modified. The most pronounced effects are an increase in the number of large membrane-bounded vesicles and in the amount of free granular material present. The conditions necessary for the fixation of the mitotic apparatus in dividing cells are discussed in the light of these observations on the isolated unit.

scholarly journals Different Ca2+-releasing abilities of sperm extracts compared with tissue extracts and phospholipase C isoforms in sea urchin egg homogenate and mouse eggs

2000 ◽  
Vol 346 (3) ◽  
pp. 743-749 ◽  
Author(s):  
Keith T. JONES ◽  
Miho MATSUDA ◽  
John PARRINGTON ◽  
Matilda KATAN ◽  
Karl SWANN
Keyword(s):  
Phospholipase C ◽  
Sea Urchin ◽  
Tissue Extracts ◽  
Sea Urchin Egg ◽  
Boar Sperm ◽  
Specific Activities ◽  
Mammalian Eggs ◽  
Mouse Eggs

A soluble phospholipase C (PLC) from boar sperm generates InsP3 and hence causes Ca2+ release when added to sea urchin egg homogenate. This PLC activity is associated with the ability of sperm extracts to cause Ca2+ oscillations in mammalian eggs following fractionation. A sperm PLC may, therefore, be responsible for causing the observed Ca2+ oscillations at fertilization. In the present study we have further characterized this boar sperm PLC activity using sea urchin egg homogenate. Consistent with a sperm PLC acting on egg PtdIns(4,5)P2, the ability of sperm extracts to release Ca2+ was blocked by preincubation with the PLC inhibitor U73122 or by the addition of neomycin to the homogenate. The Ca2+-releasing activity was also detectable in sperm from other species and in whole testis extracts. However, activity was not observed in extracts from other tissues. Moreover recombinant PLCβ1, -γ1, -γ2, -∆1, all of which had higher specific activities than boar sperm extracts, were not able to release Ca2+ in the sea urchin egg homogenate. In addition these PLCs were not able to cause Ca2+ oscillations following microinjection into mouse eggs. These results imply that the sperm PLC possesses distinct properties that allow it to hydrolyse PtdIns(4,5)P2 in eggs.

ACID-SOLUBLE NUCLEOTIDES IN THE SEA URCHIN EGG

Embryologia ◽  
1966 ◽  
Vol 9 (3) ◽  
pp. 170-183 ◽  
Author(s):  
TOMIO YANAGISAWA ◽  
NAOHIDE ISONO
Keyword(s):  
Sea Urchin ◽  
Sea Urchin Egg

Re-fertilization of the sea urchin egg

1954 ◽  
Vol 6 (2) ◽  
pp. 491-496 ◽  
Author(s):  
B. Hagström ◽  
Britt Hagström
Keyword(s):  
Sea Urchin ◽  
Sea Urchin Egg

Characterization of the sea urchin egg receptor for sperm

1996 ◽  
Vol 24 (1) ◽  
pp. 100S-100S
Author(s):  
Kay Ohlendieck ◽  
William J. Lennarz
Keyword(s):  
Sea Urchin ◽  
Sea Urchin Egg
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