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(trō pō-kŏl ă-jĕn) [″ + collagen] The basic molecular unit of collagen fibrils, composed of three polypeptide chains.


(trŏp-ŏm′ĕ-ter) [″ + metron, measure] 1. A device for measuring the rotation of the eyeballs. 2. An instrument for measuring torsion in long bones.


(trō″pō-mī′ō-sĭn) An inhibitory protein in muscle fibers; it blocks myosin from forming cross-bridges with actin until shifted by troponincalcium ion interaction.


(trō′pŏ-nĭn) An inhibitory protein in muscle fibers. The action potential at the sarcolemma causes the sarcoplasmic reticulum to release calcium ions, which bond to troponin and shift tropomyosin away from the myosin-binding sites of actin, permitting contraction. SEE: muscle for illus.

cardiac t. I Troponin I.

t. I A protein that controls actin and myosin contraction in heart muscle. It is released into the blood when heart muscles (myocardial cells) are damaged. It is a highly sensitive and specific indicator of recent myocardial infarction. SYN: cardiac troponin I.

t. T A protein, found in both skeletal and cardiac muscle, that can be detected in the blood following injury to heart muscle. Assays for it can be used as rapid tests for myocardial infarction (MI). Troponin I (which is released only by heart and not by skeletal muscles) is a more specific marker for MI than troponin T.

Trotter syndrome

(trot′ĕr) A unilateral neuralgia in the mandible, tongue, and ear. The causes are mandibular nerve lesions, deafness on the same side due to eustachian tube lesions, and damage to the levator palatini muscle resulting in kinesthesia of the soft palate.


(trof) A groove or channel.

arm t. A concave positioning device attached to a wheelchair armrest that positions the arm and prevents lateral leaning, thus encouraging postural alignment.

focal t. A three-dimensional area within which structures are accurately reproduced on a panoramic radiograph. Positioning the patient within the focal trough is critical to producing a panoramic radiograph that clearly reproduces oral structures.

gingival t. Gingival sulcus.

synaptic t. The depression in a muscle fiber adjacent to the axon terminal of a motor neuron in a myoneural junction.

Trousseau, Armand

(troo-sō′) Armand Trousseau, Fr. internist, 1801–1867.

T. sign A muscular spasm of the hand and wrist from pressure on the nerves and vessels of the upper arm. It is indicative of latent tetany, usually as a result of hypocalcemia.

T. spots Streaking of the skin with the fingernail, seen in meningitis and other cerebral diseases.


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