amoeba

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amoeba:

see amebaameba
or amoeba
, common name for certain one-celled organisms belonging to the phylum Sarcodina of the kingdom Protista. Amebas were previously classified as members of the animal kingdom.
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Amoeba

 

the order of the simplest organized protozoa of the class Sarcodina. Most live in fresh waters, a few in the soil; there are parasitic forms. They are usually of microscopic dimensions up to 50 μm, but there are also “giants” such as Pelomyxa, which grows to 2–3 mm. Amoebas have no constant body shape; their cytoplasmic body forms extrusions or pseudopodia which aid in motion and food gathering. They feed on bacteria, minute algae, and protozoa. The amoeba engulfs the food particle and from its cytoplasm the amoeba secretes digestive juices and forms a food vacuole within which the food is dissolved and is incorporated into the cytoplasm. The excretion of water (osmoregulation) and metabolic products occurs through the contractory vacuoles, which gradually accumulate waste matter and discharge it at the surface.

Amoebas ordinarily have one nucleus, but Pelomyxa is multinucleate. The majority of amoebas multiply asexually, dividing in two. The division of the body is preceded by mitosis in the nucleus. A sexual process is known only in very rare cases.

Upon subjection to unfavorable conditions—for instance, insufficient food, cold, or drying of the water body—the amoeba’s body becomes round and the surface of its cytoplasm becomes a dense protective layer; a cyst forms that is resistant to unfavorable effects of the dormant stage. Freshwater amoebas can serve as a water pollution index. Parasitic amoebas live in the intestines of various animals and man. Among these the most harmful is the dysentery amoeba (Entamoeba histolytica), which produces a severe form of amoebic dysentery in man. Infection occurs via cysts, which remain viable outside the human body.

REFERENCES

Dogel’, V. A., Iu. I. Polianskii, and E. M. Kheisin. Obshchaia protozoologiia. Moscow-Leningrad, 1962.
Seravin, L. N. Dvigatel’nye sistemy prosteishikh. Leningrad, 1967.

A. A. STRELKOV

Amoeba

[ə′mē·bə]
(invertebrate zoology)
A genus of naked, rhizopod protozoans in the order Amoebida characterized by a thin pellicle and thick, irregular pseudopodia.

amoeba

(US), ameba
any protozoan of the phylum Rhizopoda, esp any of the genus Amoeba, able to change shape because of the movements of cell processes (pseudopodia). They live in fresh water or soil or as parasites in man and animals

Amoeba

(operating system)
A distributed operating system developed by Andrew S. Tanenbaum and others of Vrije Universiteit, Amsterdam. Amoeba is only available under licence from the VUA, but is free of charge and includes all source, binaries and documentation.

http://am.cs.vu.nl/.

Amoeba

(computer, abuse)
A derogatory term for Commodore's Amiga personal computer.
References in periodicals archive ?
Diagnosis of first case of Balamuthia amoebic encephalitis in Portugal by immunofluorescence and PCR.
Amoebic cysts can survive in the environment for weeks to months.
Oklahoma State University at Sayre, Sayre, OK--"The Cause and Effect of Primary Amoebic Meniningoencephalitis"
Among the confirmed cases, amoebic dysentery and typhoid/paratyphoid topped the list with 214 and 137 cases respectively.
I am so glad now that I gave more than PS50,000 of support to the British motor industry by buying what is clearly not only a "Friday car" but one built after the local football team had lost a key match on Thursday night, and the workforce had been further distracted by an outbreak of amoebic dysentery.
Ug8fSNL-Kea) diagnosed him with primary amoebic meningoencephalitis and later performed a brain surgery on him.
Flies may carry diseases such as hepatitis A, typhoid, amoebic dysentery and polio.
It is an aquatic chess game of quick, amoebic moves and continuously advancing counter-moves, intently looking for bent rods - the surest sign of fish below.
1934 OLIN DUTRA (USA) 13 over Despite suffering amoebic dysentery and trailing by eight shots at the halfway stage, Dutra shot 71 and 72 on the 36-hole final day to pip Gene Sarazen by one shot.
It may help you find the winner to absorb the words of the legendary Bobby Jones in summing up why outsider Dutra, who had lost more than a stone through amoebic dysentery and spent time in hospital immediately before the Open, somehow managed to limp home on shaky legs even though having to play 36 holes on the final day.
But his criticism of it does not follow: "The basically amoebic description of the phenomenon cannot be stopped until we have reached a point of absurd reductionism and considered everyone" ([1966] 1971, 105).
The most common cases among the food borne illnesses related to amoebic dysentery (153), salmonellosis (113) and typhoid and paratyphoid (115).