actino-, actin-, actini-, -actinal, actis- +

1. A protein present in all cells and in muscle tissue where it plays a role in contraction: Actin is one of a large group of nitrogenous organic compounds forming the thin filaments in muscle fibers that are pulled on by myosin cross-bridges to cause a muscle contraction.

Some bacteria form actin tails to use for motility.

3. Etymology: According to A Dictionary of Scientific Terms by I.F. Henderson (Isabella Ferguson) and W.D. Henderson; Edinburgh; Oliver and Boyd Publication, 1920; this word comes from Ancient Greek ἀκτίς, "ray", "a star-shaped spicule (zoology)" + the English chemical suffix -in, -ine.

All of the other "modern" medical dictionary sources that include this actin protein term do not make any references to any etymological origins.

1. Pertaining to the oral part of a radiate animal from which the rays grow: Such sea creatures, like the jellyfish, sea anemone, or the sponge, have actinal cavities.
2. Concerning the rays or tentacles of an animal: The starfish is a good example of an actinal aquatic animal having arms extending from its center.

A sea anemone of the order Actiniaria: An actinian is a marine polyp that looks like a flower, but has oral rings of tentacles.

Actinians don't form hard skeletal structures.

1. A reference to radiation, such as sunlight or x-rays: A sunburn is an actinic burn while actinic keratosis is a skin lesion that is caused by chronic sun exposure.
2. Regarding photochemical properties: Some actinic attributes are found in containers that protect them from photo-degradation.
3. Pertaining to or designating radiant energy: An actinic ray exists in the visible and ultraviolet spectrum which produces marked chemical changes.

An injury to the skin caused by exposure to a source of ultraviolet radiation: An actinic burn is sometimes a painful redness of the skin caused by having a person's bare skin out in plain view of the sun for too long.

A basal cell or squamous cell cacinoma of the face and other exposed surfaces of the body: Actinic carcinoma is seen in people who spend prolonged periods of time in direct sunlight.

An inflammation of the conjunctiva (transparent membrane covering the eyeball): Actinic conjunctivitis can be caused by exposure to the ultraviolet radiation of sunlight or other sources, such as exposure to acetylene torches, therapeutic lamps (sun lamps), and klieg lights (powerful carbon-arc lamps producing intense light and used especially in making movies).

"Actinic" is the adjective referring to ultraviolet (UV) rays from sunlight and UV lamps.

A skin inflammation or rash resulting from exposure to sunlight, X-rays, or atomic particle radiation: Chronic or recurrent actinic dermatitis can lead to skin cancer.

Inflammation of the conjunctiva and cornea: Actinic keratoconjunctivitis includes pain, photophobia, lacrimation, and smarting of the eyelids caused by repeated flashes of bright light or ultraviolet radiation.

1. A pe-cancerous focal, scaly excrescence on the skin; solar keratoses; senile keratosis; senile wart: Actinic keratosis can affect the scalp, face, neck, or other exposed surface of skin resulting, at least partially, from long exposure to the ultraviolet rays of the sun.

These actinic keratoses or solar keratoses are growths that are usually pink or red and appear as flaky, rough scaly patches or areas of skin and they may also be light gray or brown and feel hard, rough, or gritty.
2. Etymology: "actinic" is from Greek aktis, "ray" and refers to the ultraviolet rays, as in sunlight, that can cause reaction in the skin; so, a "sunbrn" is an actinic injury while keras is a Greek element for "horn".

Such conditions can be prevented by decreasing oneself to sun exposure and by wearing sunscreen.

Actinic keratosis usually can be removed by freezing with liquid nitrogen (cryotherapy), however if a person has too many growths, a liquid or cream containing fluorouracil may be applied.

Often, during such treatment, the skin temporarily looks worse because fluorouracil causes redness, scaling, and burning of the keratoses and of the surrounding sun-damaged skin.

A relatively new drug, imiquimod, is useful in treating actinic keratosis because it helps the immune system to recognize and to destroy cancerous skin growths.

Another treatment includes cutting the keratosis away by burning them with photodynamic therapy by means of injecting ia chemical into the bloodstream that collects in the actinic keratoses and makes them more sensitive to destruction by a specialized form of light.

One of a series of chemically similar, radioactive elements with atomic numbers ranging from 89 (actinium) through 103 (lawrencium); actinide series: One kind of actinide is a neptunium, which is a hard, silvery, and ductile radioactive metal.

Some of the related chemical elements of the actinide series include actinium, thorium, palladium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium.

Descriptive of the radiate form or structure of an aquatic organism: The ray fungus and the sea anemone both display a ray-like or rayed form.

The ability of various forms of radiation to produce chemical changes or effects: Actinism is the process of changing the intrinsic property of ultraviolet light, X-rays, or sunlight in radiation into photochemical activity.

A radioactive metallic chemical element found in uranium ores: Actinium is in equilibrium with its decay products as a source of alpha rays, such as pitchblende, a mineral consisting of uranium oxide and trace amounts of radium, thorium, polonium, lead, and helium. Uraninite in a massive form is called pitchblende which is the chief uranium ore.

Actinium possesses no stable isotopes and exists in nature only as a disintegration product of uranium and thorium.

The longest lived isotope of actinium is Ac 227 with a half-life of 21.6 years. Its atomic number is 89, the melting point is 1,050°C, the estimated boiling point is 3,200°C, and its specific calculated gravity is 10.07, and a valence of 3.

A zoonotic disease caused by the bacterium "Actinobacillus lignieresii": Actinobacillosis is a contagious infection usually connected with domestic animals of cattle, and occasionally with humans.

Actinobacillosis is a sickness characterized by suppurative (causing pus) and granulomatous (inflammatory) lesions (abnormality of the skin or organs) in the respiratory tract, upper alimentary tract, skin, kidneys, joints, and other tissues.

"Actinobacillus lignieresii" infects cattle and sheep while "actinobacillosis Equuli" infects horses and pigs.

Actinobacillosis affects the soft tissues, often the tongue and cervical lymph nodes, where granulomatous swellings form and eventually break down to form abscesses.

Actinobacillosis is also called "wooden tongue", "woody tongue", or cruels.