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(ak-tin′ik) [Gr. aktis, ray] 1. Pert. to radiant energy, such as x-rays, ultraviolet light, and sunlight, esp. the photochemical effects. 2. Pert. to the ability of radiant energy to produce chemical changes. actinically (-i-k(ă)lē), adv.


(ak′tĭ-nīd″) [actin- + -ide] Any of the radioactive heavy metals designated on the periodic table of elements with atomic numbers 89–103. The actinides include naturally occurring elements, e.g., actinium and uranium, and artificial elements, e.g., fermium.


(ak″tĭ-nid′ē-ă) SEE: kiwifruit.


(ak tĭ-nĭzm) [actin- +-ism] The property of radiant energy that produces chemical changes, as in photography or heliotherapy.


(ak-tin′ē-ŭ m) [actin- + -ium] SYMB: Ac. A radioactive element, atomic mass (weight) (most stable isotope) 227, atomic number 89.

actino-, actin-

[Gr. aktis, stem aktin-, ray] 1. Prefixes meaning ray or radiation. 2. Prefixes meaning having a radiating structure, e.g., Actinomyces.


(ak″tĭ-nō″bă-sil′ŭs) [actino- + bacillus] A genus of aerobic gram-negative coccobacilli that are parasites of hoofed mammals, and, rarely, of humans. The now-preferred but less common name is Aggregatibacter. SEE: Aggregatibacter. SEE: HACEK.

A. actinomycetemcomitans A species that often colonizes the upper respiratory tract, is an important cause of periodontal infection, and is sometimes implicated in blood-culture negative endocarditis, brain abscesses, meningitis, or osteomyelitis. A. actinomycetemcomitans was formerly called Haemophilus aphrophilus; its now-preferred but less common name is Aggregatibacter aphrophilus. SEE: Aggregatibacter aphrophilus.


(ak″tĭ-nō-dĕr-mă-tīt′is) [actino- + dermatitis] Dermatitis caused by exposure to radiation.


(ak″tĭ-nō-jen′ĭk) [actino- + -genic] Radiogenic.


(ak″tĭ-nō-mī′sēz″, ak-tin″ō) [actino- + Gr. mykēs, mushroom, fungus] A genus of bacteria of the family Actinomycetaceae that contains gram-positive staining filaments. These bacteria usually cause disease in the cervicofacial (lumpy jaw), thoracic, and abdominal areas of humans.

A. antibioticus A species from which the actinomycin antibiotics are obtained.

A. bovis A species that causes actinomycosis in cattle.

A. israelii A species that causes actinomycosis in humans. It is a normal inhabitant of the mouth, but can cause abscesses in the gingiva or the jaw, as well as in the abdominal or thoracic cavities. Viewed microscopically material from these abscesses contain purulent material within which are found yellow-colored sulfur granules.


(ak″tĭ-nō-mī″sĕ-tā′lēz″) [Actinomyces] An order of bacteria that includes the families Mycobacteriaceae, Actinomycetaceae, Actinoplanaceae, Dermatophilaceae, Micromonosporaceae, Nocardiaceae, and Streptomycetaceae.


(ak″tĭ-nō-mī′sēt″) [...

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