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Eagle Effect
The Eagle effect, Eagle phenomenon, or paradoxical zone phenomenon, named after Harry Eagle who first described it, originally referred to the paradoxically reduced antibacterial effect of penicillin at high doses, though recent usage generally refers to the relative lack of efficacy of beta lactam antibacterial drugs on infections having large numbers of bacteria. The former effect is paradoxical because the effectiveness of an antibiotic generally rises with increasing drug concentration. Mechanism Proposed mechanisms: *Reduced expression of penicillin binding proteins during stationary growth phase *Induction of microbial resistance mechanisms (such as beta lactamases with short half-lives) by high drug concentrations *Precipitation of antimicrobial drug in vitro, possibly also leading to the crystallized drug being mis-detected as colonies of the microbe. *Self- antagonising the receptor with which it binds (penicillin Penicillins (P, PCN or PEN) are a group of β ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harry Eagle
Harry Eagle (July 13, 1905 – June 21, 1992) was an American physician and pathologist. He was born in New York City then studied, and later worked, at Johns Hopkins University before moving on to the National Institutes of Health. From 1961 to 1988 he worked at the Albert Einstein College of Medicine. He is best known for Eagle's minimal essential medium, which is important in understanding how human and mammalian cells reproduce. He is also known for the Eagle effect. In 1936 he was the inaugural winner of the Eli Lilly and Company-Elanco Research Award. In 1973, he was a co-winner of the Louisa Gross Horwitz Prize of Columbia University. In 1987, he was awarded the National Medal of Science for his work in the Biological Sciences Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary ... ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paradoxical Reaction
A paradoxical reaction (or paradoxical effect) is an effect of a chemical substance, such as a medical drug, that is opposite to what would usually be expected. An example of a paradoxical reaction is pain caused by a pain relief medication. Paradoxical reactions are more commonly observed in people with ADHD. Substances Amphetamines Amphetamines are a class of psychoactive drugs that are stimulants. Paradoxical drowsiness can sometimes occur in adults. Antibiotics The paradoxical effect or Eagle effect (named after Harry Eagle who first described it) refers to an observation of an increase in survivors, seen when testing the activity of an antimicrobial agent. Initially when an antibiotic agent is added to a culture media, the number of bacteria that survive drops, as one would expect. But after increasing the concentration beyond a certain point, the number of bacteria that survive, paradoxically, increases. Antidepressants In rare cases antidepressants can make users obsessive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Penicillin Binding Proteins
Penicillin-binding proteins (PBPs) are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria; the name just reflects the way by which the protein was discovered. All β-lactam antibiotics (except for tabtoxinine-β-lactam, which inhibits glutamine synthetase) bind to PBPs, which are essential for bacterial cell wall synthesis. PBPs are members of a subgroup of enzymes called transpeptidases. Specifically, PBPs are DD-transpeptidases. Diversity There are a large number of PBPs, usually several in each organism, and they are found as both membrane-bound and cytoplasmic proteins. For example, Spratt (1977) reports that six different PBPs are routinely detected in all strains of ''E. coli'' ranging in molecular weight from 40,000 to 91,000. The different PBPs occur in different numbers per cell and have varied affinities for penicillin. The PBPs are usually broadly classified into high-molecular ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Receptor Antagonist
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. Antagonist drugs interfere in the natural operation of receptor proteins.Pharmacology Guide: In vitro pharmacology: concentration-response curves " '' GlaxoWellcome.'' Retrieved on December 6, 2007. They are sometimes called blockers; examples include alpha blockers, |
Penicillin
Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from ''Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum using deep tank fermentation and then purified. A number of natural penicillins have been discovered, but only two purified compounds are in clinical use: penicillin G (intramuscular or intravenous use) and penicillin V (given by mouth). Penicillins were among the first medications to be effective against many bacterial infections caused by staphylococci and streptococci. They are still widely used today for different bacterial infections, though many types of bacteria have developed resistance following extensive use. 10% of the population claims penicillin allergies but because the frequency of positive skin test results decreases by 10% with each year of avoidance, 90% of these patients can tolerate penicillin. Additionally, those with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Group A Streptococcal Infection
Group A streptococcal infections are a number of infections with ''Streptococcus pyogenes'' a group A streptococcus (GAS). ''S. pyogenes'' is a species of beta-hemolytic gram-positive bacteria that is responsible for a wide range of infections that are mostly common and fairly mild. If the bacteria enter the bloodstream an infection can become severe and life-threatening, and is called an invasive GAS (iGAS). Infection of GAS may spread through direct contact with mucus or sores on the skin. GAS infections can cause over 500,000 deaths per year. Despite the emergence of antibiotics as a treatment for group A streptococcus, cases of iGAS are an increasing problem, particularly on the continent of Africa. There are many other species of ''Streptococcus'', including Group B streptococcus ''Streptococcus agalactiae'', and ''Streptococcus pneumoniae'', which cause other types of infections. Several virulence factors contribute to the pathogenesis of GAS, such as M protein, hemolysins ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
