amoeba

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Related to amoeboid: Amoeboid movement

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 ?
5) Culture in modified Jones' medium 86 (43) Table 4: Distribution of different morphologic forms of Blastocystis hominis in patients having irritable bowel syndrome (n=200) Morphologic form Total number (%) Vacuolated form 78 (39) Amoeboid form 4 (2) Granular form 4 (2) Cystic form 0 (0) Total 86 (43) Table 5: Therapeutic response in patients detected of having Blastocystis hominis in stool specimen Total number Number of Number of Number of of patients patients who patients in whom patients in whom detected of submitted a Blastocystis Blastocystis having repeat stool hominis was hominis was not Blastocystis specimen 7 days detected after detected after hominis after treatment treatment (%) treatment (%) 86 79 10 (12.
The crowd was no longer the "huge, harmless, amoeboid mass that took its shape from the streets, changing as they changed, yet remaining intact, of a piece" (Marshall, The Chosen Place 292).
Two basic types of tapetum are recognized in Angiosperms: secretory and amoeboid type (Pacini et al.
Alexeieff proposed a new genus for questionable amoeboid forms, which he named Nagleria in honor of Nagler's work in identifying amoebae that pass through a biflagellate stage.
r INVERTEBRATES PROTOZOA: FLAGELLATES All taxa combined a/a a/a a/a PROTOZOA: AMOEBOID Arcella sp.
Structure and seasonal dynamics of the protozoan community (heterotrophic flagellates, ciliates, amoeboid protozoa) in the plankton of a large river (river Danube, Hungary).
Protozoa were observed throughout the mucosa and submucosa and in the intestinal lumen as amoeboid structures at different stages of evolution, forming galleries throughout the mucosa.
aegilopoides [13-14] and recorded the induction of abnormal mitosis including multinucleate condition, formation of large amoeboid nuclei and polyploidy.
Other topics of the 24 papers include replicative aging in yeast, disulfide-linked protein folding pathways, regulation of MHC class I assembly and peptide binding, evolution of coloration patterns, and immunological synapses and kinapses as variations of amoeboid locomotion.
Reference: "Intelligence: Maze-Solving by an Amoeboid Organism," Toshiyuki Nakagaki, Hiroyasu Yamada, and Agota Toth, Nature, vol.
Primordial germ cells have well-defined pseudopodia (temporary protoplasmic processes) similar to amoeba, and move via amoeboid action.