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(rī″bō-nū′klē-ās) ABBR: RNase. An enzyme that catalyzes the depolymerization of ribonucleic acid (RNA) with formation of mononucleotides.


(rī″bō-noo″klē-ō-prō′tē(-ĭ)n) ABBR: RNP. A compound containing both protein and ribonucleic acid.


(rī″bō-nū′klē-ō-tīd) A nucleotide in which the sugar ribose is combined with the purine or pyrimidine base.


(rī′bŏ-prōb″) A short, radioactively labeled nucleotide sequence used in molecular hybridization to identify specific RNA or DNA sequences.


(rī′bōs) C5H10O5, a pentose sugar present in ribonucleic acids, riboflavin, and some nucleotides.


(rī′bō-sōm) A cell organelle made of ribosomal RNA and protein. Ribosomes may exist singly, in clusters called polyribosomes, or on the surface of rough endoplasmic reticulum. In protein synthesis, they are the site of messenger RNA attachment and amino acid assembly in the sequence ordered by the genetic code carried by mRNA.


(rī′bō-sĭl) The compound glycosyl, C5H9O4, formed from ribose.


(rī′bō-zīm) An RNA (ribonucleic acid) molecule that functions as an enzyme (catalyst) and either cleaves (breaks down) other forms of RNA or catalyzes other biochemical reactions occurring within cells. SYN: catalytic RNA.


(rīs) Acronym for rest, ice, compression, and elevation, the elements of management of acute soft tissue injuries.

Richter transformation, Richter syndrome

(rik′tĕr) In patients with chronic lymphocytic leukemia, the development of an aggressive lymphoma from a relatively indolent B-cell leukemia. Symptoms include rapid enlargement of lymph nodes, elevated serum tumor marker levels, drenching night sweats, and massive weight loss.


(rī′sĭn) A white, amorphous, highly toxic protein present in the seed of the castor bean, Ricinus communis. It has been used as a biological weapon.


(rĭs′ĭn-ĕn, -īn) A poisonous alkaloid present in the leaves and seeds of the castor bean plant, Ricinus communis.


(rik′ĕts) A disease of linear bone formation in children, most commonly the result of vitamin D deficiency, marked by inadequate mineralization of developing cartilage and newly formed bone, causing abnormalities in the shape, structure, and strength of the skeleton. This condition can be prevented by exposure to ultraviolet light (sunlight or artificial light) and administration of vitamin D in quantities that provide 400 I.U. of vitamin D activity per day. SYN: rachitis (2). SEE: osteomalacia.

 ETIOLOGY: Rickets has many causes, including diseases that affect vitamin D or phosphorus intake, absorption, and metabolism; renal ...

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