| bell sound | In cases of a large pulmonary cavity or of pneumothorax, a clear metallic sound obtained by striking a coin, held against the chest, by another coin, or by flicking the chest wall with one's fingernail; the sound is heard on auscultating the chest wall on the same side anteroposteriorly. Synonym: anvil sound, bell sound, coin test. (05 Mar 2000) |
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| Bell's palsy | A condition that involves the facial nerve (VII cranial nerve) and results in the paralysis of one side of the face. Bell's (facial nerve palsy) can be differentiated from a central (stroke) deficit by the inability to raise the eyebrow on the affected side. (27 Sep 1997) |
| Bell's phenomenon | A patient with peripheral facial paralysis cannot close the eyelids of the affected side without at the same time moving the eyeball upward and outward. (05 Mar 2000) |
| Bell's respiratory nerve | <anatomy, nerve> Arises from the fifth, sixth, and seventh cervical nerves (roots of brachial plexus), descends the neck behind the brachial plexus, and is distributed to the serratus anterior muscle; it is somewhat unusual in that it courses on the superficial aspect of the muscle is supplies; its paralysis results in "winged scapula". Synonym: nervus thoracicus longus, Bell's respiratory nerve, external respiratory nerve of Bell, posterior thoracic nerve. (05 Mar 2000) |
| Bell's spasm | Involuntary twitching of the facial muscles, sometimes unilateral. Synonym: Bell's spasm, convulsive tic, facial spasm, histrionic spasm, mimic convulsion, mimic spasm, mimic tic, palmus, prosopospasm. (05 Mar 2000) |
| bell stage | Third stage of tooth development, wherein the cells form the inner enamel epithelium, the stratum intermedium, the stellate reticulum, and the outer enamel epithelium; the enamel organ assumes a bell shape. (05 Mar 2000) |
| syndrome, martin-bell | Better known as the fragile X syndrome, the most common heritable form of mental retardation. Fragile x syndrome is due to mutation (changes) at the fragile x site and so perforce is x-linked (carried on the x chromosome). Although it is usually more severe in males than females, the syndrome is due to a dynamic mutation (a trinucleotide repeat) that can change in length and hence in severity from generation to generation, from person to person, and even within a given person. The fragile x syndrome is known as the martin-bell syndrome in honor of their discovery of it in 1943. (12 Dec 1998) |
| external respiratory nerve of Bell | <anatomy, nerve> Arises from the fifth, sixth, and seventh cervical nerves (roots of brachial plexus), descends the neck behind the brachial plexus, and is distributed to the serratus anterior muscle; it is somewhat unusual in that it courses on the superficial aspect of the muscle is supplies; its paralysis results in "winged scapula". Synonym: nervus thoracicus longus, Bell's respiratory nerve, external respiratory nerve of Bell, posterior thoracic nerve. (05 Mar 2000) |
| a-form DNA | <molecular biology> One of several forms that can be assumed by a double helix. A-DNA is stable in dehydrated conditions. This form is less common than the dominant form found under physiological conditions -- beta-DNA. This form is also assumed by DNA-RNA hybrid helices and by regions of double-stranded RNA. It is a right-handed helix and is a more compact form than beta-DNA. (09 Oct 1997) |
| boat form | The less stable of two conformations assumed by 6-membered cyclic sugars (pyranoses) or cyclohexane derivatives, as opposed to chair form. See: Haworth conformational formulas of cyclic sugars. (05 Mar 2000) |
| cavity preparation form | The configuration or shape of a cavity preparation. (05 Mar 2000) |
| replicative form | An intermediate stage in the replication of either DNA or RNA viral genomes that is usually double stranded, the altered, double-stranded form to which single-stranded coliphage DNA is converted after infection of a susceptible bacterium, formation of the complementary ("minus") strand being mediated by enzymes that were present in the bacterium before entrance of the viral ("plus") strand. (05 Mar 2000) |
| resistance form | The shape given to a cavity preparation that enables the dental restoration to withstand masticatory forces. (05 Mar 2000) |
| retention form | The shape of a cavity preparation that prevents displacement of the dental restoration by lateral or tipping forces as well as masticatory forces. (05 Mar 2000) |
| chair form | The more stable of two conformations assumed by 6-membered cyclic sugars (e.g., the pyranoses) or cyclohexane derivatives, as opposed to boat form. See: Haworth conformational formulas of cyclic sugars. (05 Mar 2000) |