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 ?
Notes from the field: primary amebic meningoencephalitis associated with ritual nasal rinsing--St.
The mortality rate of amebic pleural empyema is as high as 16%, which can increase to 42% due to the rupture of a hepatic abscess into the pleural space.
Of the 67 patient in this study, 11 patients were admitted with amebic liver abscess and all of them were males.
The only cases of free-living amebic meningoencephalitis included in the analytical case reviews were cases with CDC laboratory-confirmed detection of N.
We evaluated liver and renal function tests, fasting blood glucose, calcium, phosphorus, prothrombin and partial thromboplastin times, thyroid function, tuberculin skin test, serology for brucella infection, hepatitis B and C, anti-cytomegalovirus IgM and IgG, human immunodeficiency virus, serology for toxoplasma infection, and workup for hydatid cyst and amebic and fungal infections to rule out renal failure.
histolytica infection in our cases and that an early invasive amebic disease might have been evolving unless adequate early diagnosis and treatment of E.
Diagnosis of amebic liver abscess and intestinal infection with the TechLab Entamoeba histolytica II antigen detection and antibody tests.
It was effective against mobile and cystic forms of disease and due to its relatively poor systemic absorption was not used for amebic infections of the organs, particularly liver abscess (Neldner, K.
His daughter, Julia, reminisces in her introduction to Haiku: This Other World that Wright wrote haiku "at all hours: in bed as he slowly recovered from a year-long, grueling battle against amebic dysentery; in cafJs and restaurants where he counted syllables on napkins; in the country in a writing community owned by French friends, Le Moulin d' And J" (vii).
Furthermore, these special dots are no longer neatly self-contained circles; instead, they look more like amorphous amebic mutations (or like pathogens under a microscope) that leave behind motion tails and occasionally flickering offshoots.
Morbidity and mortality weekly report: Primary amebic meningioencephalitis--Arizona, Florida, and Texas.