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Chemotactic
Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. This is important for bacteria to find food (e.g., glucose) by swimming toward the highest concentration of food molecules, or to flee from poisons (e.g., phenol). In multicellular organisms, chemotaxis is critical to early development (e.g., movement of sperm towards the egg during fertilization) and development (e.g., migration of neurons or lymphocytes) as well as in normal function and health (e.g., migration of leukocytes during injury or infection). In addition, it has been recognized that mechanisms that allow chemotaxis in animals can be subverted during cancer metastasis. The aberrant chemotaxis of leukocytes and lymphocytes also contribute to inflammatory diseases such as atherosclerosis, asthma, and arthri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemotaxis Assay
Chemotaxis assays are experimental tools for evaluation of chemotactic ability of prokaryotic or eukaryotic cells. A wide variety of techniques have been developed. Some techniques are qualitative - allowing an investigator to approximately determine a cell's chemotactic affinity for an analyte - while others are quantitative, allowing a precise measurement of this affinity. Quality control In general, the most important requisite is to calibrate the incubation time of the assay both to the model cell and the ligand to be evaluated. Too short incubation time results in no cells in the sample, while too long time perturbs the concentration gradients and measures more chemokinetic than chemotactic responses. The most commonly used techniques are grouped into two main groups: Agar-plate techniques This way of evaluation deals with agar-agar or gelatine containing semi-solid layers made prior to the experiment. Small wells are cut into the layer and filled with cells and the t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertilization
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a new individual organism or offspring and initiate its development. Processes such as insemination or pollination which happen before the fusion of gametes are also sometimes informally called fertilisation. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. History In Antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic. In 1784, Spallanzani established the need of interaction between the female's ovum and male's sperm to form a zygote in frog ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Élie Metchnikoff
Ilya Ilyich Mechnikov (russian: Илья Ильич Мечников; – 15 July 1916), also spelled Élie Metchnikoff, was a Russian zoologist best known for his pioneering research in immunology. Belkin, a Russian science historian, explains why Metchnikoff himself, in his Nobel autobiography – and subsequently, many other sources – mistakenly cited his date of birth as 16 May instead of 15 May. Metchnikoff made the mistake of adding 13 days to 3 May, his Old Style birthday, as was the convention in the 20th century. But since he had been born in the 19th century, only 12 days should have been added. He and Paul Ehrlich were jointly awarded the 1908 Nobel Prize in Physiology or Medicine "in recognition of their work on immunity". Mechnikov was born in modern-day Ukraine to a Romanian noble father and a Ukrainian-Jewish mother, lived and worked for many years on the territory of what was then the Russian Empire, and later on continued his career in France. Given this com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Taxis
A taxis (; ) is the movement of an organism in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in that in the case of taxis, the organism has motility and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus. Classification Taxes are classified based on the type of stimulus, and on whether the organism's response is to move towards or away from the stimulus. If the organism moves towards the stimulus the taxis are positive, while if it moves away the taxis are negative. For example, flagellate protozoans of the genus ''Euglena'' move towards a light source. This reaction or behavior is called ''positive phototaxis'' since phototaxis refers to a response to light and the organism is moving towards the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemokinesis
Chemokinesis is chemically prompted kinesis, a motile response of unicellular prokaryotic or eukaryotic organisms to chemicals that cause the cell to make some kind of change in their migratory/swimming behaviour. Changes involve an increase or decrease of speed, alterations of amplitude or frequency of motile character, or direction of migration. However, in contrast to chemotaxis, chemokinesis has a random, non-vectorial moiety, in general. Due to the random character, techniques dedicated to evaluate chemokinesis are partly different from methods used in chemotaxis research. One of the most valuable ways to measure chemokinesis is computer-assisted (see, e.g., Image J) checker-board analysis, which provides data about migration of identical cells, whereas, in Protozoa (e.g., Tetrahymena ''Tetrahymena'', a Unicellular organism, unicellular eukaryote, is a genus of free-living ciliates. The genus Tetrahymena is the most widely studied member of its phylum. It can produce, st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Random Walk
In mathematics, a random walk is a random process that describes a path that consists of a succession of random steps on some mathematical space. An elementary example of a random walk is the random walk on the integer number line \mathbb Z which starts at 0, and at each step moves +1 or −1 with equal probability. Other examples include the path traced by a molecule as it travels in a liquid or a gas (see Brownian motion), the search path of a foraging animal, or the price of a fluctuating stock and the financial status of a gambler. Random walks have applications to engineering and many scientific fields including ecology, psychology, computer science, physics, chemistry, biology, economics, and sociology. The term ''random walk'' was first introduced by Karl Pearson in 1905. Lattice random walk A popular random walk model is that of a random walk on a regular lattice, where at each step the location jumps to another site according to some probability distribution. In a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Julius Adler (biochemist)
Julius Adler Ph.D. (born 1930) is an American biochemist. He has been an Emeritus Professor of biochemistry and genetics at the University of Wisconsin–Madison since 1997. Early life Adler was born in Edelfingen, Germany in 1930. He came to the United States in 1938 at the age of 8 and became a naturalized citizen in 1943. His family settled in Grand Forks, North Dakota where their relatives were among the first Europeans to arrive in 1880. Since he was child, Adler had been fascinated by how organisms sense and respond to the environment. Education Adler attended Harvard University and received his A.B. in Biochemical Sciences in 1952. He then studied with Henry A. Lardy at the University of Wisconsin–Madison and earned an M.S. in Biochemistry in 1954 and a Ph.D. in Biochemistry in 1957. After graduating, Adler did postdoctoral fellowships with Arthur Kornberg in the Department of Microbiology at Washington University School of Medicine (1957–59) and A. Dale Kaiser in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Henry Harris (scientist)
Sir Henry Harris (28 January 1925 – 31 October 2014) was an Australian professor of medicine at the University of Oxford who led pioneering work on cancer and human genetics in the 2000s. Early life and education Harris was born in 1925 to a Jewish family in the Soviet Union. In 1929, his family emigrated to Australia.''The Guardian'' Retrieved 11 December 2014 Harris studied at from 1937 to 1941. In 1941, he first read , but was subsequently attracted to medicine through his literary interests. He studi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phagocytosis
Phagocytosis () is the process by which a cell uses its plasma membrane to engulf a large particle (≥ 0.5 μm), giving rise to an internal compartment called the phagosome. It is one type of endocytosis. A cell that performs phagocytosis is called a phagocyte. In a multicellular organism's immune system, phagocytosis is a major mechanism used to remove pathogens and cell debris. The ingested material is then digested in the phagosome. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized. Some protozoa use phagocytosis as means to obtain nutrients. History Phagocytosis was first noted by Canadian physician William Osler (1876), and later studied and named by Élie Metchnikoff (1880, 1883). In immune system Phagocytosis is one main mechanisms of the innate immune defense. It is one of the first processes responding to infection, and is also one of the initiating branches of an adaptive immune response. Although mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different wikt:undulating, undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their biological life cycle, life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many Ectosymbiosis, ectosymbiotic and endosymbiotic species, as well as some Obligate parasite, obligate and Facultative parasite, opportunistic parasites. Ciliate species r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
