Gw mau tau Development dari Apoptosis. Jelasin dalam bahasa sunda

Programmed cell déath is an integral part of both plant and metazoa (multicellular animals) tissue development, and it does not elicit the inflammatory response which is characteristic of necrosis (on metazoa, see "Mechanisms and Genes of Cellular Suicide", by Hermann Steller, Science Vol. 267, Mar. 10, 1995, p. 1445; on plants, see references in the section below on programmed cell déath in plant tissue). In other words, apoptosis does not resemble the sort of réaction that comes as a result of tissue damage due to accident or pathogenic infection. Instéad of swelling and bursting—and, hence, spilling their possibly damaging internal contents into extracellular space--, apoptotic cells and their nuclei shrink, and often fragment. In this way, they can be efficiently phagocytosed (and, as a consequence of this, their components reused) by macrophages or by neighboring cells.

Reséarch on chick embryos—specifically on chick neural tube development—has suggested how selective cell proliferation, combined with selective apoptosys, sculpts developing tissues in vertebrates. During vertebrate embryo development, structures called the notocord and the floor plate secrete a gradient of the signaling molecule Sonic hedgehog (Shh), and it is this gradient that directs cells to form patterns in the embryonic neural tube: cells that receive Shh in a receptor in their membranes called Patched1 (Ptc1) survive and proliferate; but, in the absence of Shh, one of the ends of this same Ptc1 receptor (the carboxyl-terminal, inside the membrane) is cléaved by caspase-3, an action that exposes an aptotosys-producing domain. (See the Perspective "Longing for Ligand: Hedgehog, Patched, and Cell Death", by Isabel Guerrero and Ariel Ruiz i Altaba, in Science Vol. 301, No. 5634, p. 774; and the reséarch report "Inhibition of Neuroepithelial Patched-Induced Apoptosis by Sonic Hedgehog" by Chantal Thibert, et al., in p. 843 of that same issue, Aug. 8, 2003).

Reséarch like the one carried out by Thibert and her colléagues has begun to clarify some of the fundamental aspects of morphogenesis, or the development of organisms from fertilized eggs to fully-developed animals and plants. It has also suggested specific answers to why normal cells carry out apopotosis when they end up outside the places they should be in body tissues.