Preface

Apoptosis is programmed cell death (PCD). Since its discovery more than a century and half ago, apoptosis has been implicated in many processes in living organisms.

Apoptosis has been shown in a diverse range of healthy as well as stressed and/or diseased organisms and probably takes place in all living organisms. For example, a chapter in this book reveals the role of PCD in bone resorption under mechanical stress.

Apoptosis has also been shown in senescence in plants. The editor is convinced that the process may be involved in plant stress tolerance and sensitivity.

It is not surprising that apoptosis has been studied extensively in cancer – dysfunctional and/or dysregulated cell proliferation - research as PCD and cell multiplication maintain a balance – cell homeostasis – in healthy organisms. This book provides evidence for the observation.

> **Doctor Tobias M. Ntuli**, BSc, BScHons, Msc, PhD Post-Doctoral (Research) Fellow Division of Life Sciences Department of Life and Consumer Sciences School of Agriculture and Life Sciences College of Agriculture and Environmental Sciences Florida Campus University of South Africa South Africa

**Section 1** 

**Introduction to Apoptosis** 

**Section 1** 

**Introduction to Apoptosis** 

**Chapter 1** 

© 2012 Hongmei, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2012 Hongmei, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**Extrinsic and Intrinsic** 

Additional information is available at the end of the chapter

Zhao Hongmei

**1. Introduction** 

http://dx.doi.org/10.5772/50129

**Apoptosis Signal Pathway Review** 

family protein, caspase-3, caspase-8, caspase-9, Bid, Bax and so on.

Apoptosis, as a programmed cell death (PCD) is essential for normal cell mechanism. The word "Apoptosis" derives from Greek language "απόπτωσις" and means trees shedding their leaves in autumn, which describes the "dropping off" or "falling off" of petals from flowers, or leaves from trees. This language imaginarily described the cell death triggered by physiological and pathological stimulation. The apoptosis phenomena were first described by German Scientist Carl Vogt in 1842 year, while until 1972 year, apoptosis term was first used by John Foxton Ross Kerr group. They use apoptosis word to describe the tissue cell death. The above is the beginning of apoptosis researches and this period is the apoptosis formation; the second period about apoptosis is the biochemical level and apoptosis cell morphological changes research. In this age, people know that apoptosis accompany with cell membrane wrinkled, DNA fragmentation, cytosol calcium increased and form the apoptosis body which contain its own content so on. In this time the electron microscope play a vital role in the research. Following the apoptosis research came in the third period in recent years; scientists began to research the molecular mechanism of apoptosis and to use this cell death for clinical treatment. Some key proteins in the procession of the apoptosis have been found, such as Bcl-2

In the past, the apoptosis was focused on the caspase, a family of cysteine protease. While, using the caspase inhibitor to block the apoptosis pathway, the researchers found that the apoptosis still happen. So another pathway that is caspase-independent was found. Now, apoptosis is classified to type I, Type II, Type III PCD: type I PCD is the classic apoptosis, the well know caspase denpendent apoptosis; type II PCD's morphology characters are the appearance of the autophagic and double membrane of vacuole; type III PCD occurs without the condensate chromatin and has not been well-known. Type IIand type III PCD are the caspase-independent apoptosis. For example, the apoptosis induce factor(AIF), a mitochondria intermembrane flavoprotein, that can be released from mitochondria to
