The tension at the top of the animal pole decreases during meiotic cell division.

Meiotic maturation is essential for the reproduction procedure of many animals. During this process an oocyte produces a large egg cell and tiny polar bodies by highly asymmetric division. In this study, to fully understand the sophisticated spatiotemporal regulation of accurate oocyte meiotic division, we focused on the global and local changes in the tension at the surface of the starfish (Asterina pectinifera) oocyte in relation to the surface actin remodeling.

The effect of taxol microinjection on the microtubular structure in polar body formation of starfish oocytes.

In starfish oocytes, microtubules (MTs) form a spindle, which plays an important role in contributing to the selective loss of chromosomes and centrosomes to the polar bodies (PBs) during meiosis. When Taxol was locally injected near the germinal vesicle (GV) or the mitotic apparatus during meiosis I, PB formation was inhibited as mentioned below. In the oocytes, which were injected with Taxol after spindle formation, the spindle became large, and then the volume of the first PB also increased more than that of the control.

Imipramine inhibition of TRPM-like plasmalemmal Mg2+ transport in vascular smooth muscle cells.

Depression is associated with vascular disease, such as myocardial infarction and stroke. Pharmacological treatments may contribute to this association. On the other hand, Mg(2+) deficiency is also known to be a risk factor for the same category of diseases.

Na(+)-independent Mg(2+) transport sensitive to 2-aminoethoxydiphenyl borate (2-APB) in vascular smooth muscle cells: involvement of TRPM-like channels.

Magnesium is associated with several important cardiovascular diseases. There is an accumulating body of evidence verifying the important roles of Mg(2+)-permeable channels. In the present study, we estimated the intracellular free Mg(2+) concentration ([Mg(2+)](i)) using (31)P-nuclear magnetic resonance ((31)P-NMR) in porcine carotid arteries.

Quantitative analysis of cortical actin filaments during polar body formation in starfish oocytes.

Polar body formation is an extremely unequal cell division. In order to understand the mechanism of polar body formation, morphological changes at the animal pole were investigated in living oocytes of the starfish, Asterina pectinifera, and the amounts of cortical actin filaments were quantitatively estimated after staining the maturing oocytes with fluorescently-labeled phallotoxins using a computer and image-processing software. Formation of a bulge, which is presumed to become a polar body, and the anaphase separation of chromosomes occurred simultaneously.

Heart slice NMR.

Nuclear magnetic resonance (NMR) spectroscopy of the heart is normally carried out using whole heart preparations under coronary perfusion. In such preparations, either radical changes in ionic composition of the perfusate or applications of numerous drugs would affect coronary microcirculation. This report communicates the first (31)P NMR spectroscopy study using a heart slice preparation (left ventricular slices) superfused with extracellular medium.

Impact of plasma aldosterone levels for prediction of in-stent restenosis.

Aldosterone promotes vascular smooth muscle cell proliferation and endothelial dysfunction, suggesting the contribution to in-stent restenosis (ISR). This study evaluated any relation between plasma aldosterone levels and ISR 6 months after successful coronary stenting. We enrolled 156 consecutive patients with stable angina who underwent coronary bare metal stenting.

Temporal change in local forces and total force all over the surface of the sea urchin egg during cytokinesis.

We determined the tension over the entire surface of the sea urchin eggs during cytokinesis, on the basis of the intracellular pressure and cell shape. This allowed us to determine the temporal changes in both the distribution of local forces and the total force produced in the whole cell cortex. A spike-like peak at anaphase and a broader peak at the onset of furrowing were observed in the time-course of the total force.

Inhibition of chromosome separation in fertilized starfish eggs by kalihinol F, a topoisomerase I inhibitor obtained from a marine sponge.

Kalihinol F, a naturally occurring diterpene from a marine sponge, Acanthella sp., inhibited chromosome separation in fertilized starfish (Asterina pectinifera) eggs but allows the first cleavage to occur, thereby forming unseparated metaphase chromosomes which were elongated between the two daughter cells. The chromosomes were eventually torn off in the embryonic cells.

Effects of the phosphatase inhibitors, okadaic acid, ATPgammaS, and calyculin A on the dividing sand dollar egg.

The effects of the phosphatase inhibitors, okadaic acid (OA), adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS), and calyculin A (CL-A) on anaphase chromosome movement, cytokinesis, and cytoskeletal structures at cell division were examined by being microinjected into mitotic sand dollar eggs. When OA was injected, chromosome movement was inhibited and, moreover, chromosomes were ejected from the polar regions of the mitotic apparatus. By immunofluorescence, microtubules were observed to be severed in the OA-injected eggs, causing the smooth cell surface to be changed to an irregular surface.

Skeletogenic potential of induced secondary mesenchyme cells derived from the presumptive ectoderm in echinoid embryos.

 During the normal development of echinoids, an animal cap consisting of 8 mesomeres in a 16-cell stage embryo differentiates exclusively into ectoderm. Micromeres in an embryo at the same stage differentiate into primary mesenchyme cells (PMC) and coelomic pouch constituents. An animal cap and a quartet of micromeres were isolated from a 16-cell stage embryo and recombined to make a chimeric embryo devoid of presumptive endoderm and secondary mesenchyme cells (SMC).

Asymmetry in the Mitotic Spindle Induced by the Attachment to the Cell Surface during Maturation in the Starfish Oocyte: (meiosis/maturation/immunofluorescence/microtubule/spindle).

In order to study the dynamic behavior of the mitotic apparatus leading to unequal cleavage, we investigated the distribution of mitotic microtubules (MTs) during maturation division of starfish oocytes. When the mitotic apparatus attached to the cell surface at metaphase, in both the first and second meiotic division, it is revealed, by immunofluorescence, that the MT distribution in the spindle, as well as in the aster, became asymmetric. MTs in the peripheral half spindle increased in number compared with those in the inner half spindle.

Difference between Maturation Division and Cleavage in Starfish Oocytes: Dependency of Induced Cytokinesis on the Size of the Aster as Revealed by Transplantation of the Centrosome: (centrosome transplantation/aster formation/cytokinesis induction/maturation division/cleavage).

Using the starfish oocyte and zygote, we investigated the abilities of the centrosome at maturation and cleavage divisions to form the aster and induce cytokinesis, in order to determine differences between these divisions. The transplanted centrosome originated from both maturation and cleavage, induced an additional furrow in cleavage in the recipient cells, but did not induce abnormal polar body formation at maturation. Although it organized an additional aster in the recipient cell in both divisions, a difference in size among asters formed was recognized.

Microinjected Polystyrene Beads Move Along Astral Rays in Sand Dollar Eggs: (astral rays/fertilization/mitosis/microinjected polystyrene beads/sand dollar eggs).

Movements of polystyrene beads along astral rays of the sperm aster and the mitotic aster were investigated in eggs of the sand dollars, Clypeaster japonicus and Scaphechinus mirabilis. Polystyrene beads injected into the unfertilized egg were at a standstill in the protoplasm. After fertilization, these beads exhibited movements toward the center of the sperm aster along the rays, and finally gathered around the astral center.

MICROINJECTION OF COLCHICINE INTO SEA URCHIN EGGS.

Inhibition of cleavage by colchicine was examined by microinjecting colchicine solution into one of the blastomeres of a sea urchin egg at the two-cell stage. Cleavage was inhibited if the microinjection was made before a critical point prior to the cleavage, whereas cleavage occurred in spite of the destruction of the mitotic apparatus if the microinjection was made after the critical point. The critical point was 10 min before the mid-stage of the cleavage in Clypeaster japonicus and 8 min before the mid-stage in Temnopleurus toreumaticus at 20 ± 1°C, corresponding to the beginning of anaphase.