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Acrasin
Each species of slime mold has its own specific chemical messenger, which are collectively referred to as acrasins. These chemicals signal that many individual cells aggregate to form a single large cell or plasmodium. One of the earliest acrasins to be identified was cyclic AMP, found in the species '' Dictyostelium discoideum'' by Brian Shaffer, which exhibits a complex swirling-pulsating spiral pattern when forming a pseudoplasmodium. The term acrasin was descriptively named after Acrasia from Edmund Spenser's Faerie Queene, who seduced men against their will and then transformed them into beasts. Acrasia is itself a play on the Greek akrasia that describes loss of free will. Extraction Brian Shaffer was the first to purify acrasin, now known to be cyclic AMP, in 1954, using methanol. Glorin, the acrasin of ''P. violaceum'', can be purified by inhibiting the acrasin-degrading enzyme acrasinase with alcohol, extracting with alcohol and separating with column chromatography. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slime Mold
Slime mold or slime mould is an informal name given to a polyphyletic assemblage of unrelated eukaryotic organisms in the Stramenopiles, Rhizaria, Discoba, Amoebozoa and Holomycota clades. Most are near-microscopic; those in the Myxogastria form larger plasmodial slime molds visible to the naked eye. The slime mold life cycle includes a free-living single-celled stage and the formation of spores. Spores are often produced in macroscopic multicellular or multinucleate fruiting bodies that may be formed through aggregation or fusion; aggregation is driven by chemical signals called acrasins. Slime molds contribute to the decomposition of dead vegetation; some are parasitic. Most slime molds are terrestrial and free-living, typically in damp shady habitats such as in or on the surface of rotting wood. Some myxogastrians and protostelians are aquatic or semi-aquatic. The phytomyxea are parasitic, living inside their plant hosts. Geographically, slime molds are cosmopo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plasmodium (life Cycle)
A plasmodium is a living structure of cytoplasm that contains many nuclei, rather than being divided into individual cells each with a single nucleus. Plasmodia are best known from slime molds, but are also found in parasitic Myxosporea, and some algae such as the Chlorarachniophyta. Structure A plasmodium is an amoeboid, multinucleate, and naked mass of cytoplasm that contains many diploid nuclei. The resulting structure, a coenocyte, is created by many nuclear divisions without the process of cytokinesis, which in other organisms pulls newlydivided cells apart. In some cases, the resulting structure is a syncytium, created by the fusion of cells after division. Under suitable conditions, a plasmodium may differentiate and form fruiting bodies bearing spores at their tips. Taxonomic distribution The term plasmodium, introduced by Leon Cienkowski, usually refers to the feeding stage of slime molds; these are macroscopic mycetozoans. The multinucleate developmental stage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyclic Adenosine Monophosphate
Cyclic adenosine monophosphate (cAMP, cyclic AMP, or 3',5'-cyclic adenosine monophosphate) is a second messenger, or cellular signal occurring within cells, that is important in many biological processes. cAMP is a derivative of adenosine triphosphate (ATP) and used for intracellular signal transduction in many different organisms, conveying the cAMP-dependent pathway. History Earl Sutherland of Vanderbilt University won a Nobel Prize in Physiology or Medicine in 1971 "for his discoveries concerning the mechanisms of the action of hormones", especially epinephrine, via second messengers (such as cyclic adenosine monophosphate, cyclic AMP). Synthesis The synthesis of cAMP is stimulated by trophic hormones that bind to receptors on the cell surface. cAMP levels reach maximal levels within minutes and decrease gradually over an hour in cultured cells. Cyclic AMP is synthesized from ATP by adenylate cyclase located on the inner side of the plasma membrane and anchored at v ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dictyostelium Discoideum
''Dictyostelium discoideum'' is a species of soil-dwelling Amoeboid, amoeba belonging to the phylum Amoebozoa, infraphylum Mycetozoa. Commonly referred to as slime mold, ''D. discoideum'' is a eukaryote that transitions from a collection of unicellular amoebae into a multicellular slug and then into a fruiting body within its lifetime. Its unique asexual Biological life cycle, life cycle consists of four stages: vegetative, aggregation, migration, and culmination. The life cycle of ''D. discoideum'' is relatively short, which allows for timely viewing of all stages. The cells involved in the life cycle undergo movement, chemical signaling, and development, which are applicable to human cancer research. The simplicity of its life cycle makes ''D. discoideum'' a valuable model organism to study genetic, cellular, and biochemical processes in other organisms. Natural habitat and diet In the wild, ''D. discoideum'' can be found in soil and moist leaf litter. Its primary diet consists ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edmund Spenser
Edmund Spenser (; – 13 January 1599 Old Style and New Style dates, O.S.) was an English poet best known for ''The Faerie Queene'', an epic poem and fantastical allegory celebrating the House of Tudor, Tudor dynasty and Elizabeth I. He is recognized as one of the premier craftsmen of nascent Modern English verse, and he is considered one of the great poets in the English language. Life Edmund Spenser was born in East Smithfield, London, around the year 1552; however, there is still some ambiguity as to the exact date of his birth. His parentage is obscure, but he was probably the son of John Spenser, a journeyman clothmaker. As a young boy, he was educated in London at the Merchant Taylors' School, Northwood, Merchant Taylors' School and matriculated as a sizar at Pembroke College, Cambridge. While at Cambridge he became a friend of Gabriel Harvey and later consulted him, despite their differing views on poetry. In 1578, he became for a short time secretary to John Young (bis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Faerie Queene
''The Faerie Queene'' is an English Epic poetry, epic poem by Edmund Spenser. Books IIII were first published in 1590, then republished in 1596 together with books IVVI. ''The Faerie Queene'' is notable for its form: at over 36,000 lines and over 4,000 stanzas, it is one of the longest poems in the English language; it is also the work in which Spenser invented the verse form known as the Spenserian stanza. On a literal level, the poem follows several knights as a means to examine different virtues. The poem is also an allegory, allegorical work. As such, it can be read on several levels, including as praise (or, later, criticism) of Queen Elizabeth I. In Spenser's "Letter of the Authors", he states that the entire epic poem is "cloudily enwrapped in Allegorical devices", and that the aim of publishing ''The Faerie Queene'' was to "fashion a gentleman or noble person in virtuous and gentle discipline". Spenser presented the first three books of ''The Faerie Queene'' to Elizabet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Akrasia
Akrasia (/əˈkreɪziə/; from Ancient Greek ἀκρασία, literally meaning "lack of self-control" or "powerlessness," derived from ἀ- "without" + κράτος "power, rule") refers to the phenomenon of acting against one's better judgment—the state in which an individual intentionally performs an action while simultaneously believing that a different course of action would be better. Sometimes translated as "weakness of will" or "incontinence," akrasia describes the paradoxical human experience of knowingly choosing what one judges to be the inferior option. History In Plato's '' Protagoras'' dialogue, Socrates asks precisely how it is possible that, ''if'' one judges action A to be the best course of action, why one would do anything other than A. Classical answers In Plato's ''Protagoras'', Socrates presents a radical thesis that fundamentally denies the existence of akrasia. His famous declaration, "No one goes willingly toward the bad" (οὐδεὶς ἑκὼν κ� ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
United States National Academy Of Sciences
The National Academy of Sciences (NAS) is a United States nonprofit, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the National Academy of Medicine (NAM). As a national academy, new members of the organization are elected annually by current members, based on their distinguished and continuing achievements in original research. Election to the National Academy is one of the highest honors in the scientific field in the United States. Members of the National Academy of Sciences serve '' pro bono'' as "advisers to the nation" on science, engineering, and medicine. The group holds a congressional charter under Title 36 of the United States Code. Congress legislated and President Abraham Lincoln signed an Act of Congress (1863) establishing the National Academy of Sciences as an independent, trusted nongovernmental institution, created for the purpose of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Smithsonian Magazine
''Smithsonian'' is a magazine covering science, history, art, popular culture and innovation. The first issue was published in 1970. History The history of ''Smithsonian'' began when Edward K. Thompson, the retired editor of ''Life'' magazine, was asked by then-Secretary of the Smithsonian, S. Dillon Ripley, to produce a magazine "about things in which the Smithsonian nstitutionis interested, might be interested or ought to be interested." Thompson later recalled that his philosophy for the new magazine was that it "would stir curiosity in already receptive minds. It would deal with history as it is relevant to the present. It would present art, since true art is never dated, in the richest possible reproduction. It would peer into the future via coverage of social progress and of science and technology. Technical matters would be digested and made intelligible by skilled writers who would stimulate readers to reach upward while not turning them off with jargon. We would fin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
