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Chemotaxis
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 arthr ... [...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 ... [...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 ... [...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 zygot ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep biosphere of Earth's crust. Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of dead bodies; bacteria are responsible for the putrefaction stage in this process. In the biological communities surrounding hydrothermal vents and cold seeps, extremophile bacteria provide the nutrients needed to sustain life by converting dissolved compounds, such as hydrogen sulphide and methane, to energy. Bacteria also live in symbiotic and parasitic r ... [...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 eukaryote, is a genus of free-living ciliates. The genus Tetrahymena is the most widely studied member of its phylum. It can produce, store and react with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Theodor Wilhelm Engelmann
Theodor Wilhelm Engelmann (14 November 1843 – 20 May 1909) was a German botanist, physiologist, microbiologist, university professor, and musician whose 1882 experiment measured the effects of different colors of light on photosynthetic activity and showed that the conversion of light energy to chemical energy took place in the chloroplast. Academic history Engelmann studied natural science and medicine first at the University of Jena, from 1861 to 1862, and later at the University of Heidelberg, the University of Göttingen and the University of Leipzig. In 1867, he received a doctoral degree in medicine at Leipzig. From 1870 he taught physiology at the University of Utrecht, becoming a professor in 1877. In 1897, he began teaching physiology at the University of Berlin, where he also became the editor of the '' Archiv für Anatomie und Physiologie''. He retired in 1908, but continued to serve as editor until his death. Engelmann became a foreign member of the Royal Neth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wilhelm Pfeffer
Wilhelm Friedrich Philipp Pfeffer (9 March 1845 – 31 January 1920) was a German botanist and plant physiologist born in Grebenstein. Academic career He studied chemistry and pharmacy at the University of Göttingen, where his instructors included Friedrich Wöhler (1800-1882), William Eduard Weber (1804-1891) and Wilhelm Rudolph Fittig (1835-1910). Afterwards, he furthered his education at the universities of Marburg and Berlin. At Berlin, he studied under Alexander Braun (1805-1877) and was an assistant to Nathanael Pringsheim (1823-1894). Later on, he served as an assistant to Julius von Sachs (1832-1897) at Würzburg, In 1873 he was appointed professor of pharmacology and botany at the University of Bonn, followed by professorships at the Universities of Basel (from 1877) and Tübingen (from 1878), where he also served as director of the Botanischer Garten der Universität Tübingen. In 1887 he became a professor at the University of Leipzig and director of its botanical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Herbert Spencer Jennings
Herbert Spencer Jennings (April 8, 1868 – April 14, 1947) was an American zoologist, geneticist, and eugenicist. His research helped demonstrate the link between physical and chemical stimulation and automatic responses in lower orders of animals. Life He was born in Tonica, Illinois, on April 8, 1868, the son of George Nelson Jennings and his wife Olive Taft Jenks. He studied at the University of Michigan graduating BS in 1893 then Harvard University where he gained a further AM degree in 1895 and a PhD in 1896. In 1906 he began a long and illustrious career at Johns Hopkins University in Baltimore where he stayed until retirement in 1938. He married twice: firstly in 1898 to Louisa Burridge and secondly in 1939 to Lulu Plant. He died in Santa Monica, California, on April 14, 1947. He is buried in Forest Lawn Memorial Park in Glendale. Career Tracy Sonneborn would later write:Jennings was so struck by the continued production of hereditarily diverse clones at conjugation, ... [...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 eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their 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 ectosymbiotic and endosymbiotic species, as well as some obligate and opportunistic parasites. Ciliate species range in size from as little as 10 µm in some colpodeans to as much as 4 mm in length in some g ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
