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#5811. What does the noun crustacean mean?

#5812. What does the adjective crusty mean?

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#9768.

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2618.

2367) Julius Axelrod

Gist:

Work

The nervous systems of people and animals consist of many nerve cells with long extensions, or nerve fibers. Signals are conveyed between cells by small electrical currents and by special substances known as signal substances. The transfers occur via contacts, or synapses. Julius Axelrod studied noradrenaline, a signal substance that provides signals to increase activity in the case of aggression or danger. Among other things, in 1957 he showed how an excess of noradrenaline is released in response to nerve impulses and then returns to the place were it is stored after the signal is implemented.

Summary

Julius Axelrod (born May 30, 1912, New York, New York, U.S.—died December 29, 2004, Rockville, Maryland) was an American biochemist and pharmacologist who, along with the British biophysicist Sir Bernard Katz and the Swedish physiologist Ulf von Euler, was awarded the Nobel Prize for Physiology or Medicine in 1970. Axelrod’s contribution was his identification of an enzyme that degrades chemical neurotransmitters within the nervous system after they are no longer needed to transmit nerve impulses.

A graduate of the College of the City of New York (B.S., 1933), New York University (M.S., 1941), and George Washington University (Ph.D., 1955), Axelrod worked as a chemist in the Laboratory of Industrial Hygiene at New York City’s Health Department (1935–46) and then joined the research division of Goldwater Memorial Hospital (1946), where his studies on analgesic medications helped identify acetaminophen as the chemical responsible for relieving pain. Marketed under such trade names as Tylenol and Panadol, acetaminophen became one of the most widely used painkillers in the world. In 1949 Axelrod left the hospital to join the staff of the section on chemical pharmacology at the National Heart Institute in Bethesda, Maryland. In 1955 he moved to the staff of the National Institute of Mental Health, where he became chief of the pharmacology section of the Laboratory of Clinical Sciences. He remained at the institute until his retirement in 1984.

Axelrod’s Nobel Prize-winning research grew out of work done by Euler, specifically Euler’s discovery of noradrenaline (norepinephrine), a chemical substance that transmits nerve impulses. Axelrod, in turn, discovered that noradrenaline could be neutralized by an enzyme, catechol-O-methyltransferase, which he isolated and named. This enzyme proved critical to an understanding of the entire nervous system. The enzyme was shown to be useful in dealing with the effects of certain psychotropic drugs and in research on hypertension and schizophrenia.

Details

Julius Axelrod (May 30, 1912 – December 29, 2004) was an American biochemist. He won a share of the Nobel Prize in Physiology or Medicine in 1970 along with Bernard Katz and Ulf von Euler. The Nobel Committee honored him for his work on the release and reuptake of catecholamine neurotransmitters, a class of chemicals in the brain that include epinephrine, norepinephrine, and, as was later discovered, dopamine. Axelrod also made major contributions to the understanding of the pineal gland and how it is regulated during the sleep-wake cycle.

Education and early life

Axelrod was born in New York City, the son of Jewish immigrants from Poland, Molly (née Leichtling) and Isadore Axelrod, a basket weaver.[9] He received his bachelor's degree in biology from the College of the City of New York in 1933. Axelrod wanted to become a physician, but was rejected from every medical school to which he applied. He worked briefly as a laboratory technician at New York University, then in 1935 he got a job with the New York City Department of Health and Mental Hygiene testing vitamin supplements added to food. While working at the Department of Health, he attended night school and received his master's in sciences degree from New York University in 1941.

Research:

Analgesic research

In 1946, Axelrod took a position working under Bernard Brodie at Goldwater Memorial Hospital. The research experience and mentorship Axelrod received from Brodie would launch him on his research career. Brodie and Axelrod's research focused on how analgesics (pain-killers) work. During the 1940s, users of non-aspirin analgesics were developing a blood condition known as methemoglobinemia. Axelrod and Brodie discovered that acetanilide, the main ingredient of these pain-killers, was to blame. They found that one of the metabolites also was an analgesic. They recommended that this metabolite, acetaminophen (paracetamol, Tylenol), be used instead.

Catecholamine research

In 1949, Axelrod began work at the National Heart Institute, forerunner of the National Heart, Lung, and Blood Institute (NHLBI), part of the National Institutes of Health (NIH). He examined the mechanisms and effects of caffeine, which led him to an interest in the sympathetic nervous system and its main neurotransmitters, epinephrine and norepinephrine. During this time, Axelrod also conducted research on codeine, morphine, methamphetamine, and ephedrine and performed some of the first experiments on LSD. Realizing that he could not advance his career without a PhD, he took a leave of absence from the NIH in 1954 to attend George Washington University Medical School. Allowed to submit some of his previous research toward his degree, he graduated one year later, in 1955. Axelrod then returned to the NIH and began some of the key research of his career.

Axelrod received his Nobel Prize for his work on the release, reuptake, and storage of the neurotransmitters epinephrine and norepinephrine, also known as adrenaline and noradrenaline. Working on monoamine oxidase (MAO) inhibitors in 1957, Axelrod showed that catecholamine neurotransmitters do not merely stop working after they are released into the synapse. Instead, neurotransmitters are recaptured ("reuptake") by the pre-synaptic nerve ending, and recycled for later transmissions. He theorized that epinephrine is held in tissues in an inactive form and is liberated by the nervous system when needed. This research laid the groundwork for later selective serotonin reuptake inhibitors (SSRIs), such as Prozac, which block the reuptake of another neurotransmitter, serotonin.

In 1958, Axelrod also discovered and characterized the enzyme catechol-O-methyl transferase, which is involved in the breakdown of catecholamines.

Pineal gland research

Some of Axelrod's later research focused on the pineal gland. He and his colleagues showed that the hormone melatonin is generated from tryptophan, as is the neurotransmitter serotonin. The rates of synthesis and release follows the body's circadian rhythm driven by the suprachiasmatic nucleus within the hypothalamus. Axelrod and colleagues went on to show that melatonin had wide-ranging effects throughout the central nervous system, allowing the pineal gland to function as a biological clock. He was elected a Fellow of the American Academy of Arts and Sciences in 1971. He continued to work at the National Institute of Mental Health at the NIH until his death in 2004.

Many of his papers and awards are held at the National Library of Medicine.

Awards and honors

Axelrod was awarded the Gairdner Foundation International Award in 1967 and the Nobel Prize in Physiology or Medicine in 1970. He was elected a Foreign Member of the Royal Society in 1979 In 1992, he was awarded the Ralph W. Gerard Prize in Neuroscience. He was elected to the American Philosophical Society in 1995.

Research trainees

Solomon Snyder, Irwin Kopin, Ronald W. Holz, Rudi Schmid, Bruce R. Conklin, Ron M. Burch, Juan M. Saavedra, Marty Zatz, Richard M. Weinshilboum, Michael Brownstein, Chris Felder, Lewis Landsberg, Robert Kanterman, Richard J. Wurtman.

Personal life

Axelrod injured his left eye when an ammonia bottle in the lab exploded; he would wear an eyepatch for the rest of his life. Although he became an atheist early in life and resented the strict upbringing of his parents' religion, he identified with Jewish culture and joined several international fights against anti-Semitism. His wife of 53 years, Sally Taub Axelrod, died in 1992. At his death, on December 29, 2004, he was survived by two sons, Paul and Alfred, and three grandchildren.

Political views

After receiving the Nobel Prize in 1970, Axelrod used his visibility to advocate several science policy issues. In 1973 U.S. President Richard Nixon created an agency with the specific goal of curing cancer. Axelrod, along with fellow Nobel-laureates Marshall W. Nirenberg and Christian Anfinsen, organized a petition by scientists opposed to the new agency, arguing that by focusing solely on cancer, public funding would not be available for research into other, more solvable, medical problems. Axelrod also lent his name to several protests against the imprisonment of scientists in the Soviet Union. Axelrod was a member of the Board of Sponsors of the Federation of American Scientists and the International Academy of Science, Munich.

Any Mathematics problem and solution have Levels of Difficulty/Simplicity.

I always choose the best and most accurate method.

Technically Correct: Something which is accurate according to a strict interpretation of rules, facts, or a specific system, even if it's not the most practical or common way of thinking about it.

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#6273.

2419) Carbon Tetrachloride

Gist

Carbon tetrachloride (CCl4) is a synthetic, non-flammable, colorless liquid with a sweet odor. It was historically used in cleaning products, fire extinguishers, and as a precursor for refrigerants, but its use has been significantly reduced due to its high toxicity. It is harmful to the liver, kidneys, and central nervous system, is considered a suspected human carcinogen, and also depletes the ozone layer.  

Carbon tetrachloride (CCl4) has historically been used as a solvent, a cleaning agent, and in fire extinguishers, but its use has been largely phased out due to severe health and environmental concerns. Its primary modern use is as a feedstock for producing other chemicals, such as refrigerants, and it has a few niche industrial and laboratory applications. 

Summary

Carbon tetrachloride, also known by many other names (such as carbon tet for short and tetrachloromethane, also recognised by the IUPAC), is a chemical compound with the chemical formula CCl4. It is a non-flammable, dense, colourless liquid with a chloroform-like sweet odour that can be detected at low levels. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, an anthelmintic and a cleaning agent, but has since been phased out because of environmental and safety concerns. Exposure to high concentrations of carbon tetrachloride can affect the central nervous system and degenerate the liver and kidneys. Prolonged exposure can be fatal.

Properties

In the carbon tetrachloride molecule, four chlorine atoms are positioned symmetrically as corners in a tetrahedral configuration joined to a central carbon atom by single covalent bonds. Because of this symmetric geometry, CCl4 is non-polar. Methane gas has the same structure, making carbon tetrachloride a halomethane. As a solvent, it is well suited to dissolving other non-polar compounds such as fats and oils. It can also dissolve iodine. It is volatile, giving off vapors with an odor characteristic of other chlorinated solvents, somewhat similar to the tetrachloroethylene odor reminiscent of dry cleaners' shops.

With a specific gravity greater than 1, carbon tetrachloride will be present as a dense nonaqueous phase liquid if sufficient quantities are spilt in the environment.

Details

Carbon tetrachloride is a manufactured chemical that does not occur naturally. It is a clear liquid with a sweet smell that can be detected at low levels. It is also called carbon chloride, methane tetrachloride, perchloromethane, tetrachloroethane, or benziform. Carbon tetrachloride is most often found in the air as a colorless gas. It is not flammable and does not dissolve in water very easily. It was used in the production of refrigeration fluid and propellants for aerosol cans, as a pesticide, as a cleaning fluid and degreasing agent, in fire extinguishers, and in spot removers. Because of its harmful effects, these uses are now banned and it is only used in some industrial applications.

Carbon tetrachloride appears as a clear colorless liquid with a characteristic odor. Denser than water (13.2 lb / gal) and insoluble in water. Noncombustible. May cause illness by inhalation, skin absorption and/or ingestion. Used as a solvent, in the manufacture of other chemicals, as an agricultural fumigant, and for many other uses.

Carbon tetrachloride may be found in both ambient outdoor and indoor air. The primary effects of carbon tetrachloride in humans are on the liver, kidneys, and central nervous system (CNS). Human symptoms of acute (short-term) inhalation and oral exposures to carbon tetrachloride include headache, weakness, lethargy, nausea, and vomiting. Acute exposures to higher levels and chronic (long-term) inhalation or oral exposure to carbon tetrachloride produces liver and kidney damage in humans. Human data on the carcinogenic effects of carbon tetrachloride are limited. Studies in animals have shown that ingestion of carbon tetrachloride increases the risk of liver cancer. EPA has classified carbon tetrachloride as a Group B2, probable human carcinogen.

Additional Information

Carbon tetrachloride is a colourless, dense, highly toxic, volatile, nonflammable liquid possessing a characteristic odour and belonging to the family of organic halogen compounds, used principally in the manufacture of dichlorodifluoromethane (a refrigerant and propellant).

First prepared in 1839 by the reaction of chloroform with chlorine, carbon tetrachloride is manufactured by the reaction of chlorine with carbon disulfide or with methane. The process with methane became dominant in the United States in the 1950s, but the process with carbon disulfide remains important in countries where natural gas (the principal source of methane) is not plentiful. Carbon tetrachloride boils at 77° C (171° F) and freezes at -23° C (-9° F); it is much denser than water, in which it is practically insoluble.

Formerly used as a dry-cleaning solvent, carbon tetrachloride has been almost entirely displaced from this application by tetrachloroethylene, which is much more stable and less toxic.

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#5809. What does the noun hoard mean?

#5810. What does the noun hoax mean?

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#9766.