Category: R

Pertaining to the retina. The aldehyde of retinol, derived by the oxidative enzymatic splitting of absorbed dietary carotene, and having vitamin A activity. In the retina, retinal combines with opsins to form visual pigments. One isomer, 11-cis retinal combines with opsin in the rods (scotopsin) to form rhodopsin, or visual purple. Another, all-trans retinal (trans-r.);…

Nucleotide sequences, usually upstream, which are recognized by specific regulatory transcription factors, thereby causing gene response to various regulatory agents. These elements may be found in both promotor and enhancer regions.  

Functions and activities of the respiratory tract as a whole or of any of its parts.  

A large increase in oxygen uptake by neutrophils and most types of tissue macrophages through activation of an NADPH-cytochrome b-dependent oxidase that reduces oxygen to a superoxide. Individuals with an inherited defect in which the oxidase that reduces oxygen to superoxide is decreased or absent (granulomatous disease, chronic) often die as a result of recurrent…

The act of breathing with the lungs, consisting of inspiration, or the taking into the lungs of the ambient air, and of expiration, or the expelling of the modified air which contains more carbon dioxide than the air taken in (Blakiston’s Gould Medical Dictionary, 4th ed.). This does not include tissue respiration (= oxygen consumption)…

The ability of the eye or of a lens to make small objects that are close together, separately visible; thus revealing the structure of an object.  

Functional, metabolic, or structural changes, including necrosis, in ischemic tissues thought to result from reperfusion to ischemic areas of the tissue. The most common instance is myocardial reperfusion injury. Cellular damage that occurs after blood flow is restored to ischemic tissues.  

A backward flowing, as the casting up of undigested food, or the backward flowing of blood into the heart, or between the chambers of the heart when a valve is incompetent. The process of flowing back in the opposite direction to the usual flow, especially of bringing up partly digested food from the stomach into…

A treatment plan that specifies the dosage, the schedule, and the duration of treatment. A regulated scheme of diet, medication, exercise, or other activity designed to achieve certain ends. A fixed course of treatment, e.g. a course of drugs or a special diet. A prescribed systematic form of treatment, such as a diet, course of…

A test to determine the best eyeglasses or contact lenses to correct a refractive error (myopia, hyperopia, or astigmatism). The process of determining and then counteracting the optical errors in the eye with eye glasses. A change of direction of light rays as they enter a medium such as the eye. The measurement of the…