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Tetrodotoxin Poisoning
Tetrodotoxin (TTX) is a potent neurotoxin. Its name derives from Tetraodontiformes, an order that includes pufferfish, porcupinefish, ocean sunfish, and triggerfish; several of these species carry the toxin. Although tetrodotoxin was discovered in these fish and found in several other animals (e.g., in blue-ringed octopuses, rough-skinned newts, and moon snails), it is actually produced by certain infecting or symbiotic bacteria like ''Pseudoalteromonas'', ''Pseudomonas'', and ''Vibrio'' as well as other species found in animals. Tetrodotoxin is a sodium channel blocker. It inhibits the firing of action potentials in neurons by binding to the voltage-gated sodium channels in nerve cell membranes and blocking the passage of sodium ions (responsible for the rising phase of an action potential) into the neuron. This prevents the nervous system from carrying messages and thus muscles from contracting in response to nervous stimulation. Its mechanism of action, selective blocking of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zwitterion
In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively-charged functional groups. : With amino acids, for example, in solution a chemical equilibrium will be established between the "parent" molecule and the zwitterion. Betaines are zwitterions that cannot isomerize to an all-neutral form, such as when the positive charge is located on a quaternary ammonium group. Similarly, a molecule containing a phosphonium group and a carboxylate group cannot isomerize. Amino acids The equilibrium is established in two stages. In the first stage, a proton is transferred from the carboxyl group to a water molecule: :H2N(R)CO2H + H2O H2N(R)CO2- + H3O+ In the second stage, a proton is transferred from the hydronium ion to the amine group: :H2N(R)CO2- + H3O+ H3N+ (R)CO2- + H2O Overall, the reaction is an isomerization reaction :H2N(R)CO2H H3N+ (R)CO2- The ratio of the concentrations of the two spec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pseudomonas
''Pseudomonas'' is a genus of Gram-negative, Gammaproteobacteria, belonging to the family Pseudomonadaceae and containing 191 described species. The members of the genus demonstrate a great deal of metabolic diversity and consequently are able to colonize a wide range of niches. Their ease of culture ''in vitro'' and availability of an increasing number of ''Pseudomonas'' strain genome sequences has made the genus an excellent focus for scientific research; the best studied species include ''P. aeruginosa'' in its role as an opportunistic human pathogen, the plant pathogen '' P. syringae'', the soil bacterium '' P. putida'', and the plant growth-promoting ''P. fluorescens, P. lini, P. migulae'', and ''P. graminis''. Because of their widespread occurrence in water and plant seeds such as dicots, the pseudomonads were observed early in the history of microbiology. The generic name ''Pseudomonas'' created for these organisms was defined in rather vague terms by Walter Migula i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nassarius
''Nassarius'', common name nassa mud snails (USA) or dog whelks (UK), is a genus of minute to medium-sized sea snails, marine gastropod molluscs in the family Nassariidae.Bouchet, P.; Gofas, S. (2010). Nassarius Duméril, 1806. In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=138235 on 2010-11-30 They are scavengers. Etymology The name is derived from the Latin word "nassa", meaning a wickerbasket with a narrow neck, for catching fish. ''Nassarius'' would then mean "someone who uses such a wickerbasket for catching fish". Ecology Distribution and habitat Species within this genus are found worldwide. These snails usually live on mud flats or sand flats, intertidally or subtidally. Life habits Most ''Nassarius'' species are very active scavengers, feeding on crabs and carrion as dead fish, etc. They often burrow into marine substrates and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pomacanthidae
Marine angelfish are perciform fish of the family Pomacanthidae. They are found on shallow reefs in the tropical Atlantic, Indian, and mostly western Pacific Oceans. The family contains seven genera and about 86 species. They should not be confused with the freshwater angelfish, tropical cichlids of the Amazon Basin. Description With their bright colours and deep, laterally compressed bodies, marine angelfishes are some of the more conspicuous residents of the reef. They most closely resemble the butterflyfishes, a related family of similarly showy reef fish. Marine angelfish are distinguished from butterflyfish by the presence of strong preopercle spines (part of the gill covers) in the former. This feature also explains the family name Pomacanthidae; from the Greek πομα, ''poma'' meaning "cover" and ακάνθα, ''akantha'' meaning "thorn". Many species of marine angelfishes have streamer-like extensions of the soft dorsal and anal fins. The fish have small mouths, relat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage Clamp
The voltage clamp is an experimental method used by electrophysiologists to measure the ion currents through the membranes of excitable cells, such as neurons, while holding the membrane voltage at a set level. A basic voltage clamp will iteratively measure the membrane potential, and then change the membrane potential (voltage) to a desired value by adding the necessary current. This "clamps" the cell membrane at a desired constant voltage, allowing the voltage clamp to record what currents are delivered. Because the currents applied to the cell must be equal to (and opposite in charge to) the current going across the cell membrane at the set voltage, the recorded currents indicate how the cell reacts to changes in membrane potential. Cell membranes of excitable cells contain many different kinds of ion channels, some of which are voltage-gated. The voltage clamp allows the membrane voltage to be manipulated independently of the ionic currents, allowing the current–voltage rel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sucrose Gap
The sucrose gap technique is used to create a conduction block in nerve or muscle fibers. A high concentration of sucrose is applied to the extracellular space, which prevents the correct opening and closing of sodium and potassium channels, increasing resistance between two groups of cells. It was originally developed by Robert Stämpfli for recording action potentials in nerve fibers, and is particularly useful for measuring irreversible or highly variable pharmacological modifications of channel properties since untreated regions of membrane can be pulled into the node between the sucrose regions. History The sucrose gap technique was first introduced by in 1954 who worked with Alan Hodgkin and Andrew Huxley between 1947 and 1949. From his research, Stämpfli determined that currents moving along nerve fibers can be measured more easily when there is a gap of high resistance that reduces the amount of conducting medium outside of the cell. Stämpfli observed many problems wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Duke University
Duke University is a private research university in Durham, North Carolina. Founded by Methodists and Quakers in the present-day city of Trinity in 1838, the school moved to Durham in 1892. In 1924, tobacco and electric power industrialist James Buchanan Duke established The Duke Endowment and the institution changed its name to honor his deceased father, Washington Duke. The campus spans over on three contiguous sub-campuses in Durham, and a marine lab in Beaufort. The West Campus—designed largely by architect Julian Abele, an African American architect who graduated first in his class at the University of Pennsylvania School of Design—incorporates Gothic architecture with the Duke Chapel at the campus' center and highest point of elevation, is adjacent to the Medical Center. East Campus, away, home to all first-years, contains Georgian-style architecture. The university administers two concurrent schools in Asia, Duke-NUS Medical School in Singapore (established in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Wilson Moore
John Wilson Moore (November 1, 1920 – March 30, 2019) was an American biophysicist who pioneered the emergent power of computers, beginning in the 1950s, to reveal how signals are generated, integrated, and then travel in neurons. He is well known for his discovery (with Toshio Narahashi), that the puffer fish toxin tetrodotoxin causes death by blocking the sodium ion channels that are responsible for nerve activity. Moore was emeritus professor of Neurobiology at Duke University Medical School where he had been a member of the faculty since 1961. Moore's NEURON simulator software, begun with and now carried forward by Michael Hines, is used worldwide. Moore received the Cole Award of the Biophysical Society in 1981. Early life and education Moore was born in November 1920 in Winston-Salem, North Carolina, where his father was superintendent of the Winston-Salem public schools. He studied physics at Davidson College and entered a graduate program in physics at the University o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toshio Narahashi
Toshio Narahashi (January 30, 1927 – April 21, 2013) was an internationally known pharmacologist. He was the John Evans Professor of Pharmacology and former chair of the Department of Pharmacology at Northwestern University Feinberg School of Medicine, where he served on the faculty from 1977 to 2013. Prior, he was vice chairman of the Department of Physiology and Pharmacology at Duke University, where he served on the faculty from 1962 to 1977. He is considered by many to be the "founding father of neurotoxicology" and is credited with discovering how tetrodotoxin, the poison in puffer fish, immobilizes parts of the nervous system. Born in Tokyo, Japan, Narahashi received an undergraduate degree in agriculture from the University of Tokyo in 1948. According to the Chicago Tribune, "He began his career studying insecticides in an entomology lab. His findings in the lab helped form the basis of 26 published papers and a doctorate in neurotoxicology that he would earn in 1960 f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the extracellular space). The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, and peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane, acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose. The cell membrane controls the movement of substances in and out of cells and organelles, being selectively permeable to ions a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neuron
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. Non-animals like plants and fungi do not have nerve cells. Neurons are typically classified into three types based on their function. Sensory neurons respond to stimuli such as touch, sound, or light that affect the cells of the sensory organs, and they send signals to the spinal cord or brain. Motor neurons receive signals from the brain and spinal cord to control everything from muscle contractions to glandular output. Interneurons connect neurons to other neurons within the same region of the brain or spinal cord. When multiple neurons are connected together, they form what is called a neural circuit. A typical neuron consists of a cell body (soma), dendrites, and a single axon. The soma is a compact structure, and the axon and dend ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Voltage-gated Sodium Channels
Sodium channels are integral membrane proteins that form ion channels, conducting sodium ions (Na+) through a cell's membrane. They belong to the superfamily of cation channels and can be classified according to the trigger that opens the channel for such ions, i.e. either a voltage-change ("voltage-gated", "voltage-sensitive", or "voltage-dependent" sodium channel; also called "VGSCs" or "Nav channel") or a binding of a substance (a ligand) to the channel (ligand-gated sodium channels). In excitable cells such as neurons, myocytes, and certain types of glia, sodium channels are responsible for the rising phase of action potentials. These channels go through three different states called resting, active and inactive states. Even though the resting and inactive states would not allow the ions to flow through the channels the difference exists with respect to their structural conformation. Selectivity Sodium channels are highly selective for the transport of ions across cell membr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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