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Apoptosis
Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biology), morphology) and death. These changes include Bleb (cell biology), blebbing, Plasmolysis, cell shrinkage, Karyorrhexis, nuclear fragmentation, Pyknosis, chromatin condensation, Apoptotic DNA fragmentation, DNA fragmentation, and mRNA decay. The average adult human loses 50 to 70 1,000,000,000, billion cells each day due to apoptosis. For the average human child between 8 and 14 years old, each day the approximate loss is 20 to 30 billion cells. In contrast to necrosis, which is a form of traumatic cell death that results from acute cellular injury, apoptosis is a highly regulated and controlled process that confers advantages during an organism's life cycle. For example, the separation of fingers and toes in a developing human embryo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Programmed Cell Death
Programmed cell death (PCD) sometimes referred to as cell, or cellular suicide is the death of a cell (biology), cell as a result of events inside of a cell, such as apoptosis or autophagy. PCD is carried out in a biological process, which usually confers advantage during an organism's biological life cycle, lifecycle. For example, the Limb development, differentiation of fingers and toes in a developing human embryo occurs because cells between the fingers apoptose; the result is that the digits are separate. PCD serves fundamental functions during both plant and animal tissue development. Apoptosis and autophagy are both forms of programmed cell death. Necrosis is the death of a cell caused by external factors such as trauma or infection and occurs in several different forms. Necrosis was long seen as a non-physiological process that occurs as a result of infection or injury, but in the 2000s, a form of programmed necrosis, called necroptosis, was recognized as an alternative f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Apoptotic DNA Fragmentation
Apoptotic DNA fragmentation is a key feature of apoptosis, a type of programmed cell death. Apoptosis is characterized by the activation of endogenous endonucleases, particularly the caspase-3 activated DNase (CAD), with subsequent cleavage of nuclear DNA into internucleosomal fragments of roughly 180 base pairs (bp) and multiples thereof (360, 540 etc.). The apoptotic DNA fragmentation is being used as a marker of apoptosis and for identification of apoptotic cells either via the DNA laddering assay, the TUNEL assay, or the by detection of cells with fractional DNA content ("sub G1 cells") on DNA content frequency histograms e.g. as in the Nicoletti assay. Mechanism The enzyme responsible for apoptotic DNA fragmentation is the Caspase-Activated DNase (CAD). CAD is normally inhibited by another protein, the Inhibitor of Caspase Activated DNase (ICAD). During apoptosis, the apoptotic effector caspase, caspase-3, cleaves ICAD and thus causes CAD to become activated. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fas Receptor
The Fas receptor, also known as Fas, FasR, apoptosis antigen 1 (APO-1 or APT), cluster of differentiation 95 (CD95) or tumor necrosis factor receptor superfamily member 6 (TNFRSF6), is a protein that in humans is encoded by the ''FAS'' gene. Fas was first identified using a monoclonal antibody generated by immunizing mice with the FS-7 cell line. Thus, the name Fas is derived from ''F''S-7-''a''ssociated ''s''urface antigen. The Fas receptor is a death receptor on the surface of cells that leads to programmed cell death (apoptosis) if it binds its ligand, Fas ligand (FasL). It is one of two apoptosis pathways, the other being the mitochondrial pathway. Gene FAS receptor gene is located on the long arm of chromosome 10 (10q24.1) in humans and on chromosome 19 in mice. The gene lies on the plus ( Watson strand) and is 25,255 bases in length organized into nine protein encoding exons. Similar sequences related by evolution ( orthologs) are found in most mammals. Protein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bcl-2 Family
The Bcl-2 family (TC# 1.A.21) consists of a number of Conserved sequence, evolutionarily-conserved proteins that share Bcl-2 Sequence homology, homology (BH) domains. The Bcl-2 family is most notable for their regulation of apoptosis, a form of programmed cell death, at the mitochondrion. The Bcl-2 family proteins consists of members that either promote or inhibit apoptosis, and control apoptosis by governing mitochondrial outer membrane permeabilization (MOMP), which is a key step in the intrinsic pathway of apoptosis. A total of 25 genes in the Bcl-2 family were identified by 2008. Members of the BCL-2 family regulate apoptosis in mammals, reptiles, amphibs, fish, and other phyla of metazoan life, with exception of nematodes and insects. Their molecular structure and function, as well as their protein dynamics, are highly conserved over hundreds of millions of years in tissue forming life forms. Structure Bcl-2 family proteins have a general structure that consists of a Hydr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karyorrhexis
Karyorrhexis (from Greek κάρυον ''karyon'' 'kernel, seed, nucleus' and ῥῆξις ''rhexis'' 'bursting') is the destructive fragmentation of the nucleus of a dying cell whereby its chromatin is distributed irregularly throughout the cytoplasm. It is usually preceded by pyknosis and can occur as a result of either programmed cell death (apoptosis), cellular senescence, or necrosis. In apoptosis, the cleavage of DNA is done by Ca2+ and Mg2+ -dependent endonucleases. Image:nuclear changes.jpg, Morphological characteristics of pyknosis and other forms of nuclear destruction. File:Apoptotic neutrophil with nuclear fragmentation.jpg, Microscopy of an apoptotic neutrophil with nuclear fragmentation (H&E stain) Overview During apoptosis, a cell goes through a series of steps as it eventually breaks down into apoptotic bodies, which undergo phagocytosis. In the context of karyorrhexis, these steps are, in chronological order, pyknosis (the irreversible condensation of chrom ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Caspase
Caspases (cysteine-aspartic proteases, cysteine aspartases or cysteine-dependent aspartate-directed proteases) are a family of protease enzymes playing essential roles in programmed cell death. They are named caspases due to their specific cysteine protease activity – a cysteine in its active site nucleophilically attacks and cleaves a target protein only after an aspartic acid residue. As of 2009, there are 12 confirmed caspases in humans and 10 in mice, carrying out a variety of cellular functions. The role of these enzymes in programmed cell death was first identified in 1993, with their functions in apoptosis well characterised. This is a form of programmed cell death, occurring widely during development, and throughout life to maintain cell homeostasis. Activation of caspases ensures that the cellular components are degraded in a controlled manner, carrying out cell death with minimal effect on surrounding tissues. Caspases have other identified roles in programmed cell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyknosis
Pyknosis, or karyopyknosis, is the irreversible condensation of chromatin in the Cell nucleus, nucleus of a cell (biology), cell undergoing necrosis or apoptosis. It is followed by karyorrhexis, or fragmentation of the nucleus. Pyknosis (from Ancient Greek meaning "thick, closed or condensed") is also observed in the maturation of erythrocytes (a red blood cell) and the neutrophil (a type of white blood cell). The maturing metarubricyte (a stage in RBC maturation) will condense its nucleus before expelling it to become a reticulocyte. The maturing neutrophil will condense its nucleus into several connected lobes that stay in the cell until the end of its cell life. File:4_Bd_obs_4_680x512px.tif, Micrograph of an infarct in the biliary tract, with pyknotic nuclei (arrows) (400x). Pyknotic nuclei are often found in the zona reticularis of the adrenal gland. They are also found in the keratinocytes of the stratum corneum, outermost layer in parakeratinised epithelium. Overview of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Necrosis
Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. The term "necrosis" came about in the mid-19th century and is commonly attributed to German pathologist Rudolf Virchow, who is often regarded as one of the founders of modern pathology. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated digestion of cell components. In contrast, ''apoptosis'' is a naturally occurring programmed and targeted cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal. Cellular death due to necrosis does not follow the apoptotic signal transduction pathway, but rather various receptors are activated and result in the loss of cell membrane integrity and an uncontrolled release of products of cell death into the extracellular space. This initiates an inflammatory response in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bleb (cell Biology)
In cell biology, a bleb (or snout) is a bulge of the plasma membrane of a cell, characterized by a spherical, "blister-like", bulky morphology. It is characterized by the decoupling of the cytoskeleton from the plasma membrane, degrading the internal structure of the cell, allowing the flexibility required for the cell to separate into individual bulges or pockets of the intercellular matrix. Most commonly, blebs are seen in apoptosis (programmed cell death), but they are also seen in other non-apoptotic functions, including apocrine secretion (cell secretion by disintegration of part of a cell). ''Blebbing'', or ''zeiosis'', is the formation of blebs. Formation Initiation and expansion Bleb growth is driven by intracellular pressure (abnormal growth) generated in the cytoplasm when the actin cortex undergoes actomyosin contractions. The disruption of the membrane-actin cortex interactions are dependent on the activity of Myosin ATPase, myosin-ATPase Bleb initiation is affected ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phagocyte
Phagocytes are cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek ', "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek ''kutos,'' "hollow vessel". They are essential for fighting infections and for subsequent immunity. Phagocytes are important throughout the animal kingdom and are highly developed within vertebrates. One litre of human blood contains about six billion phagocytes. They were discovered in 1882 by Ilya Ilyich Mechnikov while he was studying starfish larvae.Ilya Mechnikov retrieved on November 28, 2008. Fro ''Physiology or Medicine 1901–192 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cancer
Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible Signs and symptoms of cancer, signs and symptoms include a lump, abnormal bleeding, prolonged cough, unexplained weight loss, and a change in defecation, bowel movements. While these symptoms may indicate cancer, they can also have other causes. List of cancer types, Over 100 types of cancers affect humans. Tobacco use is the cause of about 22% of cancer deaths. Another 10% are due to obesity, poor Diet (nutrition), diet, sedentary lifestyle, lack of physical activity or Alcohol abuse, excessive alcohol consumption. Other factors include certain infections, exposure to ionizing radiation, and environmental pollutants. infectious causes of cancer, Infection with specific viruses, bacteria and parasites is an environmental factor cau ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Kerr (pathologist)
John Foxton Ross Kerr (24 January 1934 – 4 June 2024) was an Australian pathologist. He was the first to describe the ultrastructural changes in apoptosis, and could show that they differ significantly from the changes that occur in necrosis, another form of cell death. For the first time, he placed the roles of cell death in normal adult mammals, and in disease, into scientific focus. Biography Education Kerr attended Sydney Church of England Grammar School (Shore School) in North Sydney, Australia, where he was head of the school in 1950. He was third in the Leaving Certificate in New South Wales. He then studied at the University of Queensland in Brisbane, Australia. In 1955, Kerr earned a Bachelor of Science (BSc) degree, and in 1957, a Bachelor of Medicine, Bachelor of Surgery (MBBS) in which he graduated with First Class Honours and in top place. As a medical assistant, he worked at the Royal Brisbane Hospital. In 1964, he earned a PhD at the University of London. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
