more cells dying than being replaced 26

In some cases, a cell can pose a threat to the rest of the body if it survives. in. Annals of the ICRP/ICRP Publication vol. When a cell cannot be regenerated, the body will replace it with stromal connective tissue to maintain tissue or organ function. Figure 1. What happens to dead cancer cells in the human body? Internet Explorer). Article Thierry, A. R., El Messaoudi, S., Gahan, P. B., Anker, P. & Stroun, M. Origins, structures, and functions of circulating DNA in oncology. The motto of the repair process is to fill a gap caused by the damaged cells to regain structural continuity. Peth, A., Nathan, J. 43, 259274 (2016). To generate our estimates of cellular turnover, we extracted values from the literature as detailed in the attached spreadsheet files. By measuring the fraction of the isotope carbon-14 in a tissue it is possible to infer the year in which the DNA was replicated as depicted in Figure 1. In 80 to 100 days, 30 trillion will have replenishedthe equivalent of a new you. [8] Hydropic degeneration is a severe form of cloudy swelling. But we have far more, tiny cells in our blood, which live only three to 120 days, and lining our gut, which typically live less than a week. Turning back the clock on senescent cells could switch off the ageing process. Gut 10, 612 (1969). Cells in an adult organism may be eliminated to maintain balance to make way for new cells or remove cells needed only for temporary tasks. Pillay, J. et al. Natl Acad. When plants wilt their cells are slowly. Basic Anatomical and Physiological Data for use in Radiological Protection: Reference Values. Sci. About 330 billion cells are replaced daily, equivalent to about 1 percent of all our cells. Lynch, M. & Marinov, G. K. The bioenergetic costs of a gene. Primates non-invasive in vivo imaging of CD4 cells in SHIV infected non-human primates Rockville, MD. 1 What happens when more cells are being produced that are dying? Trepel, F. Number and distribution of lymphocytes in man. It is also becoming clear that mitosis and apoptosis are toggled or linked in some way and that the balance achieved depends on signals received from appropriate growth or survival factors. And even the distinct cell populations that can rejuvenate are not replaced entirely, but only partly over a lifetime, he said. A specialty blood test, routine when on chemo, is LDH -- it detects dead cell matter in the system. CAS All of these examples point to a replacement rate of cells, that is characteristic of different tissues and in different conditions, but which makes it abundantly clear that for many cell types renewal is a part of their story. Cell Mol. In fact, even if you're middle aged, most of you may be just 10 years old or less. PLoS ONE 8, e67590 (2013). When a cells DNA is damaged, it will typically detect the damage and try to repair it. Scientists at the Weizmann Institute of Science in Rehovot, Israel, have finally pinned down the speed and extent of this turnover. About a third of our body mass is fluid outside of our cells, such as plasma, plus solids, such as the calcium scaffolding of bones. Cellular swelling (or cloudy swelling) may occur due to cellular hypoxia, which damages the sodium-potassium membrane pump; it is reversible when the cause is eliminated. Apoptosis removes cells during development. Google Scholar. Fatty change is also known as fatty degeneration, fatty metamorphosis, or fatty steatosis. Bill Nye Cells Flashcards | Quizlet Biochemical events lead to characteristic cell changes and death. Health Anatomy Does the human body replace itself every 7 years? Analytical cookies are used to understand how visitors interact with the website. USA 112, 1569015695 (2015). 1 Detailed distribution of the cellular turnover rate of human cells by cell type. Direct link to Click here's post Maybe the DNA of the cell, Posted 6 years ago. A. M., Tesselaar, K. & de, B. R. Current best estimates for the average lifespans of mouse and human leukocytes: reviewing two decades of deuterium-labeling experiments. nerve. For instance, this may be the case for cells with DNA damage, pre-cancerous cells, and cells infected by viruses. Go to: Open Questions Brown, C. T., Olm, M. R., Thomas, B. C. & Banfield, J. F. Measurement of bacterial replication rates in microbial communities. J. Physiol. When you purchase through links on our site, we may earn an affiliate commission. Biological context of DNA repair. What are the heaviest organs in the human body? [12], Immunogenic cell death or immunogenic apoptosis is a form of cell death caused by some cytostatic agents such as anthracyclines, oxaliplatin and bortezomib, or radiotherapy and photodynamic therapy (PDT). A large addition of 14C in 19551963 is the result of nuclear bomb tests. Am. The distribution of cellular turnover in the human body Thanks for reading Scientific American. It contrasts with necrosis (death by injury), in which the dying cells contents spill out and cause inflammation. R.S. A single cell divides to make two cells and these two cells then divide to make four cells, and so on. [6] Called "non-apoptotic programmed cell-death" (or "caspase-independent programmed cell-death"), these alternative routes to death are as efficient as apoptosis and can function as either backup mechanisms or the main type of PCD. You also have the option to opt-out of these cookies. What effects accomplishments did Francisco have. cells being replaced so as to retain normal function of cells. When the skin (or any other tissue, for that matter) is wounded, the wound-healing process initiates the generation of new fibroblasts to produce scar collagen, which is different from the collagen in normal skin. Landgraf, P. et al. If you're seeing this message, it means we're having trouble loading external resources on our website. Am. 32 (Pergamon, 2002). Oncol. https://doi.org/10.1152/ajpendo.1990.258.6.E990 (1990). https://doi.org/10.1098/rspb.2018.0789 (2018). But some cells, such as skin cells or blood cells are dividing all the time. Extended Data Fig. What are the Causes of Apoptosis? Direct link to Abhi's post Mostly because when they . If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked. Actually, cancer treatments are in fact triggers of apoptosis. Article [9] The stages of cellular necrosis include pyknosis; clumping of chromosomes and shrinking of the nucleus of the cell, karyorrhexis; fragmentation of the nucleus and break up of the chromatin into unstructured granules, and karyolysis; dissolution of the cell nucleus. This process is called cell division. Programmed cell death and how it is different from necrosis (cell death due to injury). But what about the very slow tissues that take years or a lifetime? Biological cellceasing to carry out its functions, Zhang J, Xu X, Liu Y. Grey line represents the gestation period. Stephen, A. the processes are no longer able to happen because the cells don't USA 116, 2048220488 (2019). Can banks make loans out of their required reserves? Virchows Arch. Visualization performed using the online tool at http://bionic-vis.biologie.uni-greifswald.de/. It wasn't mentioned in this article but one of my lecturers went on about it. Add to this, that our cells have a thing called telomeres, which cap off the ends of our DNA. In the brain, cell renewal can be even more leisurely. Cells that undergo apoptosis go through a different and much more orderly process. Sometimes, if a small mistake happens during finger or toe development, apoptosis may be incomplete (leading, for instance, to fused toes). Many cells in the human body have the built-in ability to undergo apoptosis (in the same way that they have the built-in ability to copy their DNA or break down fuels). Shrestha, R. P. et al. Klin. 121, 14401446 (2003). Apoptosis mainly prevents hurting a multi-cellular organism, but i guess if the apoptotic signal is mutated (certain enzymes or receptors in the apoptotic pathway working not the way they should) it could result in mass apoptosis in tissues. Cell death is the event of a biological cell ceasing to carry out its functions. What Frisen found is that the body's cells largely replace themselves every 7 to 10 years. Lodish H, Berk A, Matsudaira P, Kaiser CA, Krieger M, Scott MP, Zipursky SL, Darnell J. you died What happens at the cellular level to cause the wilted appearance? Programmed cell death (PCD) is cell death mediated by an intracellular program. Crowe, P. T. & Marsh, M. N. Morphometric analysis of small intestinal mucosa IV. Macallan, D. C. et al. Cells continue to grow (and be replaced) around it, but it remains hence why scars remain for years and years, far longer than the 14-day lifespan of the skin cells around them. Risk - free offer! It occurs with hypokalemia due to vomiting or diarrhea. What happen when more cells are being produced than are dying? [3] Biochemical events lead to characteristic cell changes (morphology) and death. Language links are at the top of the page across from the title. When cells become damaged or die the body makes new cells to replace them. Direct link to Saundra Boykin's post If cells undergo Apoptosi, Posted 7 years ago. Haynes RH (1988). Direct link to Ivana - Science trainee's post By default yes. A reduction in intracellular ATP can have a number of functional and morphologic consequences during cell injury. Reprod. R. Soc. This may be the result of the natural process of old cells dying and being replaced by new ones, as in programmed cell death, or may result from factors such as diseases, localized injury, or the death of the organism of which the cells are part. At what age do cells stop regenerating? - TimesMojo 4 Cellular mass accumulation rate during development. A., Mock, D. M. & Veng-Pedersen, P. A novel physiology-based mathematical model to estimate red blood cell lifespan in different human age groups. Name one large single cell that is very easy to see. Get the most important science stories of the day, free in your inbox. Communications Biology In necrosis, a cell undergoes swelling, followed by uncontrolled rupture of the cell membrane with cell contents being expelled. Skin cells for instance keep dying and How quickly do different cells in the body replace themselves? Comp. [8] It occurs as a result of repeated stimulation of specific T-cell receptors (TCR) and it helps to maintain the periphery immune tolerance. Revisiting the ratio of bacterial to host cells in humans. Natl Acad. This often causes inflammation in the tissue surrounding the dead cell. Aug. 2, 2005 Whatever your age, your body is many years younger. Welle, S. & Nair, K. S. Relationship of resting metabolic rate to body composition and protein turnover. Lynnerup, N., Kjeldsen, H., Heegaard, S., Jacobsen, C. & Heinemeier, J. Radiocarbon dating of the human eye lens crystallines reveal proteins without carbon turnover throughout life. Those two groups therefore make up the giant majority of the turnover. Cell damage can be reversible or irreversible. Am. Science Monday: If Our Cells Replace Themselves, Why Do We Have Sender, R., Fuchs, S. & Milo, R. Revised estimates for the number of human and bacteria cells in the body. However, those DNA damages that remain un-repaired can have detrimental consequences. Physiol. . For multicellular organism we have things like apoptosis and necrosis,what about organism with only one cell? Amongst other causes, this can be due to physical, chemical, infectious, biological, nutritional or immunological factors. DNA damages may block replication or gene transcription. The energy from the dead cells is partly recycled to make other white cells. For rapidly renewing tissues common labeling tricks can be useful as with the nucleotide analog BrdU. The global 14C Levels in the environment are shown in red. & Creamer, B. Three-dimensional structure of the human small intestinal mucosa in health and disease. a. In the meantime, to ensure continued support, we are displaying the site without styles On the right-hand side, the overall mean value is shown with its standard error estimate. Some For eukaryotes, oxidative reactions are a major source of DNA damage (see DNA damage (naturally occurring) and Sedelnikova et al.[23]). Watch Out: Tornado Alley Is Migrating Eastward. Create your free account or Sign in to continue. 21 Mar 2013. Blood 114, 328338 (2009). In aerobically growing bacteria, ROS appear to be a major source of DNA damage, as indicated by the observation that 89% of spontaneously occurring base substitution mutations are caused by introduction of ROS-induced single-strand damages followed by error-prone replication past these damages. However, some common features of PCD are highly conserved in both plants and metazoa. Cell damage (also known as cell injury) is a variety of changes of stress that a cell suffers due to external as well as internal environmental changes. This cookie is set by GDPR Cookie Consent plugin. Survival of the eukaryotes depends upon interactions between many cell types, and it is essential that a balanced distribution of types be maintained. These effects include: DNA damage (or RNA damage in the case of some virus genomes) appears to be a fundamental problem for life. These blockages can lead to cell death. Extended Data Fig. & de Maat, C. E. M. Erythropoiesis and mean redcell lifespan in normal subjects and in patients with the anaemia of active rheumatoid arthritis. 577-584. Could you please clarify the role that calcium plays in programmed cell death? PANoptosis is regulated by multifaceted macromolecular complexes termed PANoptosomes. The result is the increasing level of decrepitude we call ageing. The cells between your embryonic fingers died in a process called. What does it mean to call a minor party a spoiled? Stone, K. C., Mercer, R. R., Gehr, P., Stockstill, B. The cookie is used to store the user consent for the cookies in the category "Performance". [16] A form of programmed necrosis, called necroptosis, has been recognized as an alternative form of programmed cell death. In Cardiac Regeneration and Repair, 2014. have the right products. Weinstein, G. D., McCullough, J. L. & Ross, P. A. Cell death in health and disease: angiogenesis review series. Nat. Direct link to Bi Hong MInh Phc's post is there any cell that do, Posted 5 years ago. Do any cells last a lifetime? | Questions | Naked Scientists One of the bodies many partners in the immune system is the macrophage cell. Apoptosis is an orderly process in which the cells contents break down and are packaged into small packets of membrane for garbage collection by immune cells. The cells contents can leak out and damage neighbouring cells, and may also trigger inflammation. What is so different about the brain, and how does it repair itself? Language links are at the top of the page across from the title. Different types of cells have a different life span depending on We can connect this lifetime to the fact calculated in the vignette on How many cells are there in an organism? that there are about 31013 red blood cells to infer that about 100 million new red blood cells are being formed in our body every minute! Thyroid Gland: Facts, function & diseases, Siberian cave filled with mammoth, rhino and bear bones is ancient hyena lair. Intracellular water exchange for measuring the dry mass, water mass and changes in chemical composition of living cells. mitosis In unicellular organisms, cell division is the means of reproduction; in multicellular organisms, it is the means of tissue growth and maintenance. [8] In the other words AICD is the negative regulator of activated T-lymphocytes. J. Respir. PubMed Central DNA damage appears to play a key role in mammalian aging, and an adequate level of DNA repair promotes longevity (see DNA damage theory of aging and reference.[28]). Most cells in our bodies divide and are replaced when they die, but we can't rely on this process forever, especially when our DNA is setting the timer. Successful cancer cells, however, manage to duck both internal and external cues that would normally trigger apoptosis. so the 2 daughter cells that are produced are diploid. Dermatol. To be more concrete, our skin cells are known to constantly be shed and then renewed. Regeneration of parenchyma cells, or the functional cells, of an organism. Clin. In programmed cell death, cells undergo "cellular suicide" when they receive certain cues. When damaged [9] Therefore, an alteration of the process may lead to autoimmune diseases. ), the Israeli Council for Higher Education via the Weizmann Data Science Research Center and by a research grant from Madame Olga Klein Astrachan (R.S.). USA 95, 708713 (1998). Discover our latest special editions covering a range of fascinating topics from the latest scientific discoveries to the big ideas explained. WHAT IS CELL DEATH? - Pathosomes Every day, more than 50 billion cells die in our bodies. However, its also important that some cells of our bodies. Cells in the liver regenerate at a somewhat slower pace, Bergmann and his colleagues reported June 15 in the journal Cell Systems. It also eliminates pre-cancerous and virus-infected cells, although successful cancer cells manage to escape apoptosis so they can continue dividing. Knowledge awaits. AAPS J. Crosby, W. H. et al. Cells that do are eliminated right away by apoptosis. Dana, Most dead cells are filtered via the liver, which is part of why enzymes can get out of range. PLoS ONE 3, 13 (2008). Forever young: Senescent cells and secret to stopping ageing For example, have you ever wondered how your fingers formed? ISSN 1078-8956 (print). Watch on Regulation of Differentiation, Cell Division, and Apoptosis Virchow was correct when he concluded that cells arise from others cells, i.e., new cells are born through the division of one cell into two through the process of mitosis. Front Biosci. PubMed Hayes, A.W., Ed. In contrast, DNA damages are altered structures that cannot, themselves, be replicated. Nature Medicine The long held dogma in the cardiac biology community was that these cells do not replace themselves. Birth year of the individual is indicated by a vertical line. This article was originally published on Live Science on April 4, 2011 and rewritten on June 28, 2022. There is some evidence that certain symptoms of "apoptosis" such as endonuclease activation can be spuriously induced without engaging a genetic cascade, however, presumably true apoptosis and programmed cell death must be genetically mediated. [14] It has been used to describe the real-time changes during cell death, detected by flow cytometry.[18]. Also, the fragments of the dying cell display a lipid molecule called phosphatidylserine on their surface. Waterlow, J. C. Protein Turnover (CABI, 2006). Posted 7 years ago. J. Cells on the surface of our bodies or in the lining of our gut are sloughed off and discarded. Similarly, we have all had the experience of cutting ourselves only to see how new cells replaced their damaged predecessors. 6, 235243 (1992). Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. Not exactly. Because the damaged cells plasma membrane can no longer control the passage of ions and water, the cell swells up, and its contents leak out through holes in the plasma membrane. When cells become damaged or die the body makes new cells to replace them. Google Scholar. Gastroenterology 67, 11431154 (1974). [16], The term "cell necrobiology" has been used to describe the life processes associated with morphological, biochemical, and molecular changes which predispose, precede, and accompany cell death, as well as the consequences and tissue response to cell death. Try 3 issues for just 5 when you subscribe to BBC Science Focus Magazine. Hoath, S. B. How can the replacement rates of the cells in various tissues in our body be measured? & Sill, A. J. Quantitative histology of the gastric mucosa: man, dog, cat, guinea pig, and frog. 35, 347376 (2016). Direct link to Greacus's post Apoptosis mainly prevents, Posted 7 years ago. In multicellular organisms, cell death in response to DNA damage may occur by a programmed process, apoptosis. Lurie, S. & Mamet, Y. Apostoaei, A. J. This allows them to divide out of control and accumulate mutations (changes in their DNA). (Image credit: FG Trade via Getty Images). Other examples of apoptosis during normal development include the loss of a tadpoles tail as it turns into a frog, and the removal of unneeded neurons in as neural circuits in the brain are wired.. The term was initially coined to broadly define investigations of the changes that accompany cell death, detected and measured by multiparameter flow- and laser scanning- cytometry. This article was originally published with the title "A New You in 80 Days" in Scientific American 324, 4, 76 (April 2021), Mark Fischetti is a senior editor at Scientific American. (2004). It is now thought that in a developmental context cells are induced to positively commit suicide whilst in a homeostatic context; the absence of certain survival factors may provide the impetus for suicide. Small vacuoles of fat accumulate and become dispersed within cytoplasm. Darwich, A. S., Aslam, U., Ashcroft, D. M. & Rostami-Hodjegan, A. Meta-analysis of the turnover of intestinal epithelia in preclinical animal species and humans. But other types of neurons stay with a person for their entire lifetime, Bergmann said. Presentation of the cellular mass turnover rates of human cells at higher resolution that in Fig. Where is the tallest General Electric Building located? [7] Using these dating methods, it was inferred that fat cells (adipocytes) replace at a rate of 86% per year (BNID 103455). Apoptosis (from Ancient Greek: , romanized: apptsis, lit. These cookies track visitors across websites and collect information to provide customized ads. The normal PCV for a cat is 25-45%, and any PCV below 25% is considered anemic. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation. But today we can use radiation therapy or special treatment to render many types cancerous cell harmless. Growth dynamics of gut microbiota in health and disease inferred from single metagenomic samples. Am. Am. Am. 10 May 2023, Scientific Reports What specific section of the world do cannibals do not live? J. Leukoc. Related: Why haven't we cloned a human yet? Apoptosis is the process of programmed cell death (PCD) that may occur in multicellular organisms. But while most cells are regenerated, the processes involved become progressively unreliable over time. How is it possible for mantle rock to flow? Spalding, K. L., Bhardwaj, R. D., Buchholz, B. 2. are divided into their subpopulation. Stay up to date on the latest science news by signing up for our Essentials newsletter. Measurement of cell proliferation by labeling of DNA with stable isotope-labeled glucose: Studies in vitro, in animals, and in humans. Future US, Inc. Full 7th Floor, 130 West 42nd Street, Gastroenterology 103, 17831789 (1992). Natl Acad. http://bionic-vis.biologie.uni-greifswald.de/. 93, 185192 (2000). Large analysis says the long-held idea is flat-out wrong, Distortions in space-time could put Einstein's theory of relativity to the ultimate test, See the 'monster' sunspot that launched the Carrington Event, the most devastating solar storm in recorded history, Where do honey bees come from? Answer (1 of 4): NEURONS The life and death of them Until recently, most neuroscientists thought we were born with all the neurons we were ever going to have. Biol. Direct link to Saloni's post How does apoptosis relate, Posted 2 years ago. & Wilson, G. D. Cell production rates in human tissues and tumours and their significance. To clarify the presentation, Fig. Extended Data Fig. Our analysis pipeline consists of about 15 different Jupyter notebooks that use the data extracted from the literature as inputs for generating our estimates. 26, 405417 (2000). Tomasetti, C., Poling, J., Roberts, N. J., London, N. R. & Pittman, M. E. Cell division rates decrease with age, providing a potential explanation for the age-dependent deceleration in cancer incidence. J. Med. [1] Cell death occurs when the severity of the injury exceeds the cell's ability to repair itself. What is it called when cells are made then die? 3 Distribution of lifespan measurements of epithelial cells in the different segments of the gastrointestinal tract (GIT). PLoS Biol. including articles by more than 150 Nobel Prize winners. Anemia means a decreased number of red blood cells in circulation. 2:d61-77. The body can make more cells to replace the damaged cells keeping the organ or tissue intact and fully functional. What physically happens to Your Body Right after death? Cell death, clearance and immunity in the skeletal muscle We provide the code for generating all numeric estimates at https://github.com/milo-lab/cellular_turnover. Mostly because when they have an allergic reaction something can trigger it which can cause exploding cells, Duplication of digit 4 is preceded by reduced apoptosis and expanded chondrogenesis in the posterior limb mesenchyme, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2844952/. Performance cookies are used to understand and analyze the key performance indexes of the website which helps in delivering a better user experience for the visitors. In 80 to 100 days, 30 trillion will have replenishedthe equivalent of a new you. 52, 511515 (1974). J. Physiol. Thus, foreign bodies, such as tattoo dyes, implanted in the dermis will remain.". As noted by Haynes,[18] the subunits of DNA are not endowed with any peculiar kind of quantum mechanical stability, and thus DNA is vulnerable to all the "chemical horrors" that might befall any such molecule in a warm aqueous medium. What is the relationship between Commerce and economics? Table 1: Cell renewal rates in different tissues of the human body. Fibroblasts, immune cells, pericytes, and inflammatory cells are the most common types of stromal cells.[16]. Her work has appeared in Scientific American, Wired UK, Popular Science and Youth Today, among others. Proc. https://doi.org/10.1038/s41591-020-01182-9. 43, 393408 (1975). [15] In the average adult between 50 and 70 billion cells die each day due to apoptosis. Open Access Our daily newsletter arrives just in time for lunch, offering up the day's biggest science news, our latest features, amazing Q&As and insightful interviews. Explain Like I'm Five is the best forum and archive on the internet for Several different repair processes can remove DNA damages (see chart in DNA repair). The ultrastructural changes of reversible cell injury include: In fatty change, the cell has been damaged and is unable to adequately metabolize fat. The cells in our bodies live for anything from a few hours, in the case of certain types of white blood cells, to a few weeks, for skin cells, to many decades, in the case of most brain cells. 94, 595601 (2013). Blood 117, 33433352 (2011). Cell damage can be reversible or irreversible. Cancer Metastasis Rev. Overtime, the cells die. An important internal source of DNA damage in both prokaryotes and eukaryotes is reactive oxygen species (ROS) formed as byproducts of normal aerobic metabolism. & Jimbow, K. Role of light in human skin color variation. What years of time was the separate but equal doctrine the law of the land in the US? Polygon areas represent the fraction of total daily cell replacement for which the cell category accounts. Many types of liver diseases and conditions injure healthy liver cells, causing cell death and inflammation. Others are slower, like bones. is there any cell that doesn't undergo apoptosis. CAS When it affects many cells in an organ, it causes some pallor, increased turgor, and increase in weight of the organ. The human body replaces its own cells regularly. Cancer and aging as consequences of un-repaired DNA damage. Biol. In other words, after about seven years of cellular replication, you're an entirely new collection of cells, inside and out. When cells are damaged by harmful factors (such as injury or toxic chemicals), they usually spill their guts as they die. This research was supported by the European Research Council (project NOVCARBFIX 646827), Israel Science Foundation (grant 740/16), Beck-Canadian Center for Alternative Energy Research, Dana and Yossie Hollander, Ullmann Family Foundation, Helmsley Charitable Foundation, Larson Charitable Foundation, Wolfson Family Charitable Trust, Charles Rothschild, Selmo Nussenbaum (R.M. It is an energy-dependent process mediated by proteolytic enzymes called caspases, which trigger cell death through the cleaving of specific proteins in the cytoplasm and nucleus.

Manitoba Senior Hockey Provincials 2023, Who Owns The Yellowstone Ranch In Real-life, Articles M