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H SAKAI

Publications and source records attributed to H SAKAI.

At least 19 recordsLinked to original sources
PubMed1962

Studies on sulfhydryl groups during cell division of sea urchin egg. IV. Contractile properties of the thread model of KLCl-soluble protein from the sea urchin egg.

A KCl-soluble protein fraction can be extracted from the water-insoluble residue of the homogenate of sea urchin eggs which contains three major components separable by ultracentrifugation. When the extract is stirred in acetone or distilled water, a fibrous precipitate appears which has a strong birefringence positive in the direction of the long axis. When the fraction is squirted through a slender tubing, it precipitates in the form of a thread. The thread model contracts vigorously under the action of di-, tri-, and tetravalent metal ions; the contraction can be reversed by EDTA. The contraction and the elongation of the thread model can be repeated many times. The thread model contracts also in the presence of dehydroascorbic acid, cystine, oxidized glutathione, or other oxidizing agents, and this contraction is reversed by reducing agents such as cysteine or ascorbic acid. When -SH groups of the thread model are blocked by various -SH reagents, the contraction by metal ions is inhibited to some extent. As mechanisms of the contraction, electrostatic forces between metal ions and negative charges of the thread model are essential for metal ion-induced contraction and oxidation of -SH groups of the thread model for the contraction by oxidizing reagents.

Animals↗
PubMed1962

Studies on sulfhydryl groups during cell division of sea urchin egg. V. Change in contractility of the thread model in relation to cell division.

The contractility of the thread model prepared from the KCl-soluble proteins of the egg and in vivo factors for the contraction are investigated in Hemicentrotus, Anthocidaris, and Pseudocentrotus eggs. The contractility of the thread model induced by metal ions or cystine changes during development in the characteristic pattern of high at the metaphase and low at the monaster and the interkinetic stages. The change in contractility is paralleled by the change in the -SH content of the protein. The water-soluble fraction of the eggs has activity in causing contraction of the thread model. This activity changes during development in the same way as the contractility itself. The contraction of the thread induced by the water-soluble fractions is accompanied by a decrease in the -SH content of the thread. The activity of the water-soluble fraction in inducing the contraction is proportional to its ability to decrease the number of -SH groups. On boiling, the activity is largely destroyed. The activity is due to two components, one being non-dialyzable and the other dialyzable. Separately each component has little effect, but when mixed, the activity of the original sample is completely restored.

Animals↗
PubMed1960

Studies on sulfhydryl groups during cell division of sea urchin egg. II. Mass isolation of the egg cortex and change in its--SH groups during cell division.

Masses of cortices of both unfertilized and fertilized sea urchin eggs can be isolated by crushing eggs in hypotonic MaCl(2) (0.1 M) solution. The amount of cortical material in terms of protein-N increases steadily after fertilization until the monaster stage and thereafter remains almost constant until well into the two-cell stage. The amount of bound-SH per protein-N of the egg cortex also increases after fertilization, reaches a maximum value at the amphiaster stage and thereafter decreases rapidly as the cleavage of the cell proceeds.

Animals↗
PubMed1960

Studies on sulfhydryl groups during cell division of sea urchin egg. III. SH groups of KC1-soluble proteins and their change during cleavage.

Sea urchin egg proteins extracted with KCl are mostly TCA-soluble and, conversely, those extracted with TCA are KCl-soluble. Both groups are water-insoluble and show fluctuations in-SH content during the division cycle. The fluctuation of the-SH groups of the KCl-soluble protein of the whole egg is due to a -SHright harpoon over left harpoon-S-S- interchange within the freely reacting groups and not within the sluggish and masked -SH groups of the protein. The -SH content of the KCl-soluble protein of the egg cortex also fluctuates in a similar way.

Cell Division↗