Overview

Comprehensive Description

Description of Entamoeba

Pseudopodia as semi-eruptive anterior bulges with clear hyaline caps. Endoplasm granular with vesicles but without crystals or contractile vacuole. Nucleus ring-like, with peripheral granules and a central endosome. Cysts round and smooth. Mature cysts of some species multinucleate. Many varieties reported. Habitat: parasite of the intestinal mucosa of man, apes, monkeys, dogs, cats, pigs, rats, cattle and other animals; some species commensal in mouth; can migrate to other tissues via the bloodstream; causes mild to severe diarrhoea on occasion lethal. Type species: Entamoeba coli Cassigrandi & Barbagallo, 1895.
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Entamoeba moshkovskii

Entamoeba moshkovskii is part of the Entamoeba family and is, according to the Center for Disease Control a "free living amoeba."[1] It is found in areas with polluted water sources, and is prevalent in places such as Malaysia, India, and Bangladesh, but more recently has made its way to Turkey, Australia, and North America. This amoeba is said to rarely infect humans, but recently this has changed. It is in question as to whether it is pathogenic or not. AP,[2] Some of the symptoms that often occur are diarrhea, weight loss, bloody stool, and abdominal pain. The first known human infection also known as the "Laredo strain" of Entamoebic mushkovskii was in Laredo, Texas in 1991.[3] It is known to affect people of all ages and genders.CID,[4]

Characteristics[edit]

Entamoeba moshkovskii's exact characteristics are "indistinguishable" from that of Entamoeba histolytica and Entamoeba dispar unless a polymerase chain reaction test is done. This is the only circumstance in which you can distinguish between the three of them.[5]

Transmission[edit]

Entamoeba moshkovskii is transmitted by contact or ingestion of any unclean water sources. It is known to be found in areas with polluted water such as brackish coastal pools, river line sediments, and originally sewage.[6]

Signs and symptoms[edit]

Signs and symptoms include diarrhea, bloody stool, weight loss, abdominal pain (could last up to 2–4 weeks).

Risk Factors[edit]

Risk factors include the use or ingestion of polluted sources of water. Swimming in any areas with polluted water is also a risk. Most of the cases reported are in rural areas.

Diagnosis[edit]

Diagnosis with Entamoeba moshkovskii is difficult to do until you are showing symptoms. Until the symptoms begin you will be asymptomatic. The amoeba will form cysts and trophozoites in the Gastrointestinal tract. This can cause abdominal pain and diarrhea. Once symptoms start to occur the standard means of diagnosing are a series of stool sample examinations and serological testing, and if necessary a colonoscopy or a biopsy of intestinal amebic legions or draining of liver abcesses if present .CMR,[7] They are checking to see if there is any indication of the amoeba within the feces. In order to do this they have to make several stool smears and carefully observe it under the microscope. At this point if you are positive, it will usually come down to three choices for a diagnosis. The choices being ''Entamoeba moshkovskii'', ''Entamoeba histolytica'', or ''Entamoeba dispar''. These three choices are, in the view of the microscope, "indistinguishable."CDC,[8] This is the point where a doctor makes the call for what is most common (Entamoeba histolytica) or something a little more rare (Entamoeba mushkovskii).If they choose to go with what is common they will treat with "entamoebic chemotherapy" CDC,.[9] This can be a fatal for the patient's sake if it is not Entamoeba histolytica, but this happens quite often. If the choice is to further examine the diagnosis,they will have to do a "polymerase chain reaction".CMR,[10] This is the only way, to our knowledge to differentiate between the three amoebas and effectively diagnose.

Treatment[edit]

Although treatments are still being researched there are some ways to treat Entamoebic moshkovskii. Since this particular amoeba is resistant to emitin CMR,[11] they typically treat using an anti-protozoan or antiamoebic therapy.CMR,[12] In tropical regions anyone with cysts in their stool is treated with an anti-protozoan.

Prevention[edit]

Preventive methods are to only utilize clean water sources -whether it be for ingestion, cleaning, or recreation - and good hygiene such as hand-washing.

References[edit]

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Entamoeba

Entamoeba is a genus of Amoebozoa found as internal parasites or commensals of animals.

In 1875, Fedor Lösch described the first proven case of amoebic dysentery in St Petersburg, Russia. He referred to the amoeba he observed microscopically as 'Amoeba coli'; however it is not clear whether he was using this as a descriptive term or intended it as a formal taxonomic name.[1] The genus Entamoeba was defined by Casagrandi and Barbagallo for the species Entamoeba coli, which is known to be a commensal organism.[2] Lösch's organism was renamed Entamoeba histolytica by Fritz Schaudinn in 1903; he later died, in 1906, from a self-inflicted infection when studying this amoeba. For a time during the first half of the 20th century the entire genus Entamoeba was transferred to Endamoeba, a genus of amoebas infecting invertebrates about which little is known. This move was reversed by the International Commission on Zoological Nomenclature in the late 1950s, and Entamoeba has stayed 'stable' ever since.

Species[edit]

Several species are found in humans. Entamoeba histolytica is the pathogen responsible for 'amoebiasis' (which includes amoebic dysentery and amoebic liver abscesses), while others such as Entamoeba coli (not to be confused with Escherichia coli) and E. dispar [3] are harmless. With the exception of Entamoeba gingivalis, which lives in the mouth, and E. moshkovskii, which is frequently isolated from river and lake sediments, all Entamoeba species are found in the intestines of the animals they infect. Entamoeba invadens is species that can cause a disease similar to E. histolytica but in reptiles. In contrast to other species, E. invadens forms cysts in vitro in the absence of bacteria and is used as a model system to study this aspect of the life cycle. Many other species of Entamoeba have been described and it is likely that many others remain to be found.

Structure[edit]

Entamoeba cells are small, with a single nucleus and typically a single lobose pseudopod taking the form of a clear anterior bulge. They have a simple life cycle. The trophozoite (feeding-dividing form) is approximately 10-20 μm in diameter and feeds primarily on bacteria. It divides by simple binary fission to form two smaller daughter cells. Almost all species form cysts, the stage involved in transmission (the exception is E. gingivalis). Depending on the species, these can have one, four or eight nuclei and are variable in size; these characteristics help in species identification.

Classification[edit]

Entamoeba belongs to the Archamoebae, which like many other anaerobic eukaryotes lack mitochondria. This group also includes Endolimax and Iodamoeba, which also live in animal intestines and are similar in appearance to Entamoeba, although this may partly be due to convergence. Also in this group are the free-living amoebo-flagellates of the genus Mastigamoeba and related genera.[4] Certain other genera of symbiotic amoebae, such as Endamoeba, might prove to be synonyms of Entamoeba but this is still unclear.

Culture[edit]

Fission[edit]

Studying Entamoeba invadens, David Biron of the Weizmann Institute of Science and coworkers found that about one third of the cells are unable to separate unaided and recruit a neighboring amoeba (dubbed the "midwife") to complete the fission.[5] He writes:

When an amoeba divides, the two daughter cells stay attached by a tubular tether which remains intact unless mechanically severed. If called upon, the neighbouring amoeba midwife travels up to 200 μm towards the dividing amoeba, usually advancing in a straight trajectory with an average velocity of about 0.5 μm/s. The midwife then proceeds to rupture the connection, after which all three amoebae move on.

They also reported a similar behavior in Dictyostelium.[6]

Since E.histolytica does not form cysts in the absence of bacteria, E.invadens has become used as a model for encystation studies as it will form cysts under axenic growth conditions, which simplifies analysis. After inducing encystation in E.invadens, DNA replication increases initially and then slows down. On completion of encystation, predominantly tetra-nucleate cysts are formed along with some uni-, bi- and tri-nucleate cysts.[7]

Differentiation and cell biology[edit]

Uni-nucleated trophozoites convert into cysts in a process called encystation. The number of nuclei in the cyst varies from 1 to 8 among species and is one of the characteristics used to tell species apart. Of the species already mentioned, Entamoeba coli forms cysts with 8 nuclei while the others form tetra-nucleated cysts. Since E. histolytica does not form cysts in vitro in the absence of bacteria, it is not possible to study the differentiation process in detail in that species. Instead the differentiation process is studied using E. invadens, a reptilian parasite that causes a very simiilar disease to E. histolytica and which can be induced to encyst in vitro. Until recently there was no genetic transfection vector available for this organism and detailed study at the cellular level was not possible. However, recently a transfection vector was developed and the transfection conditions for E. invadens were optimised which should enhance the research possibilities at the molecular level of the differentiation process.[8][9]

References[edit]

  1. ^ Lösch, F. (1875) Massenhafte Entwickelung von Amöben im Dickdarm. Virchow's Archiv 65: 196-211.
  2. ^ Casagrandi O & Barbagallo P (1895) Ricerche biologiche e cliniche suli' Amoeba coli (Lösch). (Nota preliminare). Bull. Accad. Gioenia Sci. Nat. Catania 39: 4.
  3. ^ Diamond LS and Clark CG (1993). "A redescription of Entamoeba histolytica Schaudinn, 1903 (emended Walker, 1911) separating it from Entamoeba dispar Brumpt, 1925". Journal of Eukaryotic Microbiology 40 (3): 1340–344. PMID 8508172. 
  4. ^ Stensvold CR, Lebbad M, and Clark CG (January 2012). "Last of the human protists: the phylogeny and genetic diversity of Iodamoeba.". Molecular Biology and Evolution. (in press) (1): 39–42. doi:10.1093/molbev/msr238. PMID 21940643. 
  5. ^ Biron D, Libros P, Sagi D, Mirelman D, Moses E (2001). "Asexual reproduction: 'Midwives' assist dividing amoebae". Nature 410 (6827): 430. doi:10.1038/35068628. PMID 11260701. 
  6. ^ Nagasaki, A and Uyeda, T., Q., P.; Chemotaxis-Mediated Scission Contributes to Efficient Cytokinesis in Dictyostelium, Cell Motility and the Cytoskeleton; Vol. 65; Issue 11; Article first published online: 7 AUG 2008
  7. ^ Singh N, Bhattacharya S, Paul J (2010). "Entamoeba invadens: Dynamics of DNA synthesis during differentiation from trophozoite to cyst". Experimental Parasitology 127 (2): 329–33. doi:10.1016/j.exppara.2010.08.013. PMID 20727884. 
  8. ^ Singh, Nishant; Ojha, Sandeep, Bhattacharya, Alok, Bhattacharya, Sudha (2012). "Establishment of a transient transfection system and expression of firefly luciferase in Entamoeba invadens". Molecular and Biochemical Parasitology 183 (1): 90– 93. doi:10.1016/j.molbiopara.2012.01.003. 
  9. ^ Singh, Nishant; Ojha, Sandeep, Bhattacharya, Alok, Bhattacharya, Sudha (2012). "Stable transfection and continuous expression of heterologous genes in Entamoeba invadens". Molecular and Biochemical Parasitology 184 (1): 9–12. doi:10.1016/j.molbiopara.2012.02.012. 
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