Sperm just say NO to egg cells.When a sperm penetrates it, an egg releases a wave of stored calcium ions. This surge is the universal signal telling an egg to divide and develop. But what exactly is it about the sperm's arrival that triggers this calcium message? It's a squirt of nitric oxide nitric oxide or nitrogen monoxide, a colorless gas formed by the combustion of nitrogen and oxygen as given by the reaction: energy + N2 + O2 → 2NO; m.p. −163.6°C;; b.p. −151.8°C;. from the sperm, report Richard C. Kuo of Stanford University School of Medicine Stanford University School of Medicine is affiliated with Stanford University and is located at Stanford University Medical Center in Stanford, California, adjacent to Palo Alto and Menlo Park. and his colleagues in the Aug. 10 NATURE. Nitric oxide, or NO, has earned high marks in recent years as a versatile signaling molecule A signaling molecule is a chemical involved transmitting information between cells. Such molecules are released from the cell sending the signal, cross over the gap between cells, and interact with receptors in another cell, triggering a response in that cell. used by cells. Kuo and his colleagues recently discovered that sea urchin sea urchin, spherical-shaped echinoderm with movable spines covering the body. The body wall is a firm, globose shell, or test, made of fused skeletal plates and marked by regularly arranged tubercles to which the movable spines are attached. sperm, especially the heads, contain an enzyme that can synthesize To create a whole or complete unit from parts or components. See synthesis. the gas. They further found that this enzyme goes into action just as a sperm infiltrates an egg. The nitric oxide produced triggers the release of calcium, which prompts the egg to make more nitric oxide and free more calcium. The investigators even demonstrated that simply raising the amount of nitric oxide within an egg activates the cell to start developing. In contrast, adding a nitric oxide inhibitor to eggs made them resistant to activation by sperm. The biologists are now examining whether sperm and eggs from other animals, including people, use this gas attack to start a new life. |
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