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Epitestosterone
Epitestosterone, or isotestosterone, also known as 17α-testosterone or as androst-4-en-17α-ol-3-one, is an endogenous steroid and an epimer of the androgen sex hormone testosterone. It is a weak competitive antagonist of the androgen receptor (AR) and a potent 5α-reductase inhibitor. Structurally, epitestosterone differs from testosterone only in the configuration at the hydroxy-bearing carbon, C17. Epitestosterone is believed to form in a similar way to testosterone; a 1993 study found that around 50% of epitestosterone production in human males can be ascribed to the testis, although the exact pathway of its formation is still the subject of research. It has been shown to accumulate in mammary cyst fluid and in the prostate. Epitestosterone levels are typically highest in young males; however, by adulthood, most healthy males exhibit a testosterone to epitestosterone ratio (T/E ratio) of about 1:1. Society and culture Detection of athletic doping It has been shown that ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doping (Sport)
In competitive sports, doping is the use of banned athletic performance-enhancing drugs by athletic competitors as a way of cheating in sports. The term ''doping'' is widely used by organizations that regulate sporting competitions. The use of drugs to enhance performance is considered unethical, and therefore prohibited, by most international sports organizations, including the International Olympic Committee. Furthermore, athletes (or athletic programs) taking explicit measures to evade detection exacerbate the ethical violation with overt deception and cheating. The origins of doping in sports go back to the very creation of sport itself. From ancient usage of substances in chariot racing to more recent controversies in doping in baseball, doping in tennis, doping at the Olympic Games, and doping at the Tour de France, popular views among athletes have varied widely from country to country over the years. The general trend among authorities and sporting organizations over ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australian Senate
The Senate is the upper house of the bicameral Parliament of Australia, the lower house being the House of Representatives. The composition and powers of the Senate are established in Chapter I of the Constitution of Australia. There are a total of 76 senators: 12 are elected from each of the six Australian states regardless of population and 2 from each of the two autonomous internal Australian territories (the Australian Capital Territory and the Northern Territory). Senators are popularly elected under the single transferable vote system of proportional representation. Unlike upper houses in other Westminster-style parliamentary systems, the Senate is vested with significant powers, including the capacity to reject all bills, including budget and appropriation bills, initiated by the government in the House of Representatives, making it a distinctive hybrid of British Westminster system, Westminster bicameralism and American-style bicameralism. As a result of propor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Androstanes
An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes the embryological development of the primary male sex organs, and the development of male secondary sex characteristics at puberty. Androgens are synthesized in the testes, the ovaries, and the adrenal glands. Androgens increase in both males and females during puberty. The major androgen in males is testosterone. Dihydrotestosterone (DHT) and androstenedione are of equal importance in male development. DHT ''in utero'' causes differentiation of the penis, scrotum and prostate. In adulthood, DHT contributes to balding, prostate growth, and sebaceous gland activity. Although androgens are commonly thought of only as male sex hormones, females also have them, but at lower levels: they function in libido and sexual arousal. Also, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
5α-Reductase Inhibitors
5α-Reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in three metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism. There are three isozymes of 5α-reductase encoded by the genes SRD5A1, SRD5A2, and SRD5A3. 5α-Reductases catalyze the following generalized chemical reaction: :a 3-oxo-5α-steroid + acceptor a 3-oxo-Δ4-steroid + reduced acceptor Where a 3-oxo-5α-steroid and acceptor are substrates, and a corresponding 3-oxo-Δ4-steroid and the reduced acceptor are products. An instance of this generalized reaction that 5α-reductase type 2 catalyzes is: :dihydrotestosterone + NADP+ \rightleftharpoons testosterone + NADPH + H+ where dihydrotestosterone is the 3-oxo-5α-steroid, NADP+ is the acceptor and testosterone is the 3-oxo-Δ4-steroid and NADPH the reduced acceptor. Production and activity The enzyme is produced in many tissues in both males and females, in the re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
17α-Estradiol
17α-Estradiol (also known as 17α-E2, 17-epiestradiol, alfatradiol, or estra-1,3,5(10)-triene-3,17α-diol) is a minor and weak endogenous steroidal estrogen that is related to 17β-estradiol (better known simply as estradiol). It is the C17 epimer of estradiol. It has approximately 100-fold lower estrogenic potency than 17β-estradiol. The compound shows preferential affinity for the ERα over the ERβ. Although 17α-estradiol is far weaker than 17β-estradiol as an agonist of the nuclear estrogen receptors, it has been found to bind to and activate the brain-expressed ER-X with a greater potency than that of 17β-estradiol, suggesting that it may be the predominant endogenous ligand for the receptor. Aging Supplementation with 17α-Estradiol increases the median lifespan of male mice by 19%, while not affecting female lifespan. This treatment does not lead to feminization of male mice. 17α-Estradiol furthermore alleviates age-related metabolic and inflammatory dysfuncti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ESPN
ESPN (originally an initialism for Entertainment and Sports Programming Network) is an American international basic cable sports channel owned by ESPN Inc., owned jointly by The Walt Disney Company (80%) and Hearst Communications (20%). The company was founded in 1979 by Bill Rasmussen along with his son Scott Rasmussen and Ed Eagan. ESPN broadcasts primarily from studio facilities located in Bristol, Connecticut. The network also operates offices and auxiliary studios in Miami, New York City, Las Vegas, Seattle, Charlotte, Washington, D.C., and Los Angeles. James Pitaro currently serves as chairman of ESPN, a position he has held since March 5, 2018, following the resignation of John Skipper on December 18, 2017. While ESPN is one of the most successful sports networks, there has been criticism of ESPN. This includes accusations of biased coverage, conflict of interest, and controversies with individual broadcasters and analysts. , ESPN reaches approximately ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotope-ratio Mass Spectrometry
Isotope-ratio mass spectrometry (IRMS) is a specialization of mass spectrometry, in which mass spectrometric methods are used to measure the relative abundance of isotopes in a given sample. This technique has two different applications in the earth and environmental sciences. The analysis of 'stable isotopes' is normally concerned with measuring isotopic variations arising from mass-dependent isotopic fractionation in natural systems. On the other hand, radiogenic isotope analysis involves measuring the abundances of decay-products of natural radioactivity, and is used in most long-lived radiometric dating methods. Introduction The isotope-ratio mass spectrometer (IRMS) allows the precise measurement of mixtures of naturally occurring isotopes. Most instruments used for precise determination of isotope ratios are of the magnetic sector type. This type of analyzer is superior to the quadrupole type in this field of research for two reasons. First, it can be set up for multiple- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotope
Isotopes are two or more types of atoms that have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), and that differ in nucleon numbers ( mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have almost the same chemical properties, they have different atomic masses and physical properties. The term isotope is formed from the Greek roots isos ( ἴσος "equal") and topos ( τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by Scottish doctor and writer Margaret Todd in 1913 in a suggestion to the British chemist Frederick Soddy. The number of protons within the atom's nucleus is called its atomic number and is equal to the number of electrons in the neutral (non-ionized) atom. Each atomic n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organic Synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one of the most important branches of organic chemistry. There are several main areas of research within the general area of organic synthesis: '' total synthesis'', '' semisynthesis'', and ''methodology''. Total synthesis A total synthesis is the complete chemical synthesis of complex organic molecules from simple, commercially available petrochemical or natural precursors. Total synthesis may be accomplished either via a linear or convergent approach. In a ''linear'' synthesis—often adequate for simple structures—several steps are performed one after another until the molecule is complete; the chemical compounds made in each step are called synthetic intermediates. Most often, each step in a synthesis refers to a separate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2006 Tour De France
The 2006 Tour de France was the 93rd edition of the Tour de France, one of cycling's Grand Tours. It took place between the 1st and the 23rd of July. It was won by Óscar Pereiro following the disqualification of Floyd Landis. Due to the United States Anti-Doping Agency announcing on August 24, 2012, that they had disqualified Lance Armstrong, a former teammate of Landis, from all of his results since August 1, 1998, including his seven Tour de France titles from 1999 to 2005, this is also the first Tour to have an overall winner since 1998. By terms of margin of victory the 2006 Tour was the 3rd closest of all time. The Tour began with a prologue in Strasbourg, on the French-German border, and ended on Sunday 23 July in Paris. The distance of the course (run counterclockwise around France) was . The race was the third fastest in average speed. Along the way, the cyclists passed through six different countries including France, The Netherlands (a stop at Valkenburg in Stage 3) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Floyd Landis
Floyd Landis (born October 14, 1975) is an American former professional road racing cyclist. He finished first at the 2006 Tour de France, and would have been the third non-European winner in the event's history, but was disqualified after testing positive for performance-enhancing drugs. The competition was ultimately won by Óscar Pereiro. Landis was an all-around rider, with special skills in climbing, time-trialing, and descending. He turned professional in 1999 with the Mercury Cycling Team, joined the U.S. Postal Service team in 2002, and moved to the Phonak Hearing Systems team in 2005. In January 2010, a French judge issued a national arrest warrant for Landis on computer hacking charges related to the 2006 doping allegations. Until 2010, Landis maintained his innocence and mounted a defense. Although his legal team documented inconsistencies in the handling and evaluation of his urine samples, the disqualification was upheld. He was suspended from professional compe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
False Positive
A false positive is an error in binary classification in which a test result incorrectly indicates the presence of a condition (such as a disease when the disease is not present), while a false negative is the opposite error, where the test result incorrectly indicates the absence of a condition when it is actually present. These are the two kinds of errors in a binary test, in contrast to the two kinds of correct result (a and a ). They are also known in medicine as a false positive (or false negative) diagnosis, and in statistical classification as a false positive (or false negative) error. In statistical hypothesis testing the analogous concepts are known as type I and type II errors, where a positive result corresponds to rejecting the null hypothesis, and a negative result corresponds to not rejecting the null hypothesis. The terms are often used interchangeably, but there are differences in detail and interpretation due to the differences between medical testing and stat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
