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Radial keratotomy
A surgical procedure in which incisions are made into the epithelium of the cornea to correct refractive error.
Radiation
Use of high-energy radiation from x-rays, neutrons, and other sources to kill cancer cells and shrink tumors.
Radiation colitis
Inflammation of the colon from radiation therapy.
Radiation therapy
Treatment with high-energy rays to kill or damage cancer cells. External radiation therapy is the use of a machine to aim high- energy rays at the cancer. Internal radiation is the placement of radioactive material inside the body as close as possible to the cancer.
Radical mastectomy
Surgical removal of the entire breast, the pectoral muscles, and the ancillary lymph nodes.
Radical prostatectomy
Surgery to remove the prostate along with the two seminal vesicle glands attached to the prostate.
Radical retropubic prostatectomy
An operation to remove the entire prostate gland and seminal vesicles through the lower abdomen.
Radiculopathy
Pinched nerve usually from a herniated, or slipped, disk; can cause a shooting pain often described as an electrical feeling.
Radioactive
Giving off radiation.
Radioisotope
A radioactive material injected into the body so that a nuclear scanner can make pictures.
Radionuclide scan
An imaging scan in which a small amount of radioactive substance is injected into the vein. A machine measures levels of radioactivity in certain organs, thereby detecting any abnormal areas or tumors.
Radionuclide scanning
An exam that produces pictures (scans) of internal parts of the body. The patient is given an injection or swallows a small amount of radioactive material. A machine called a scanner then measures the radioactivity in certain organs.
Radionuclide Scans
Any of a variety of medical imaging methods that rely on atomic isotopes that decay and emit radiation.
Radionuclide ventriculography
A diagnostic procedure used to determine the shape and size of the heart's chambers.
Radiopharmaceutical (TRACER OR RADIONUCLIDE)
The basic, radioactively-tagged compound necessary to produce a nuclear medicine image.
Range of motion
Measurement of the extent to which a joint can go through all of its normal range of movements.
Rapid gastric emptying
See dumping syndrome.
Recessive
A gene that is phenotypically manifest in the homozygous state but is masked in the presence of a dominant allele.
Recessive allele
A gene that is expressed only when its counterpart allele on the matching chromosome is also recessive (not dominant). Autosomal recessive disorders develop in persons who receive two copies of the mutant gene, one from each parent who is a carrier. (See Dominant allele.)
Recombinant DNA molecules
A combination of DNA molecules of different origin that are joined using recombinant DNA technologies.
Recombinant DNA technologies
Procedures used to join together DNA segments in a cell- free system (an environment outside a cell or organism). Under appropriate conditions, a recombinant DNA molecule can enter a cell and replicate there, either autonomously or after it has become integrated into a cellular chromosome.
Recombination
The natural process of breaking and rejoining DNA strands to produce new combinations of genes and, thus, generate genetic variation. Gene crossover during meiosis.
Recommended dietary allowance (RDA)
Recommendations for daily intake of specific nutrients for groups of healthy individuals, as set by the Food and Nutrition Board of the National Research Council of the National Academy of Science.
Rectal manometry
Test that uses a thin tube and balloon to measure pressure and movements of the rectal and anal sphincter muscles.
Rectocele
Condition in which weakening of the lower vaginal wall causes the rectum to bulge into the vagina.
Rectum
Lower end of the large intestine, leading to the anus.
Reflex sympathetic dystrophy (RSD)
Caused by an abnormal sympathetic muscle reflex, giving rise to a response that is out of proportion to, and inconsistent with, the injury.
Reflux (REGURGITATION)
Condition that occurs when gastric juices, or small amounts of food from the stomach, flow back into the esophagus and mouth.
Reflux esophagitis
Irritation of the esophagus due to stomach contents flowing back into the esophagus.
Refractive error
The degree to which light reaches the back of the eye; includes myopia, hyperopia, and astigmatism.
Regional anesthetic
An anesthetic used to numb a portion of the body.
Regional enteritis
See Crohn's disease.
Regulatory regions or sequences
A DNA base sequence that controls gene expression.
Regurgitation, gastrointestinal
See reflux.
Regurgitation, heart
Backward flow of blood caused by a defective heart valve.
Rehabilitation
The process of restoring a part of the body or a person to near-normal functioning after an injury or disease.
Remission
Disappearance of the signs and symptoms of cancer. When this happens, the disease is said to be 'in remission'. Remission can be temporary or permanent.
Renal
Relating to the kidneys.
Repeat sequences
The length of a nucleotide sequence that is repeated in a tandem cluster.
Reproductive cells
Egg and sperm cells. Each mature reproductive cell carries a single set of 23 chromosomes.
Required surgery
An operation which is necessary to continue quality of life. Required surgery may not have to be done immediately, like emergency surgery.
Resolution
Degree of molecular detail on a physical map of DNA, ranging from low to high.
Respiration
Gas exchange from air to the blood and from the blood to the body cells.
Respiratory system
The group of organs responsible for carrying oxygen from the air to the bloodstream and for expelling carbon dioxide.
Resting tremor
A tremor of a limb that increases when the limb is at rest.
Restriction enzyme cutting site
A specific nucleotide sequence of DNA at which a particular restriction enzyme cuts the DNA. Some sites occur frequently in DNA (e.g., every several hundred base pairs), others much less frequently (rare- cutter; e.g., every 10,000 base pairs).
Restriction enzymes
Enzymes that can cut strands of DNA at specific base sequences.
Restriction fragment length polymorphism (RFLP)
Variation between individuals in DNA fragment sizes cut by specific restriction enzymes; polymorphic sequences that result in RFLPs are used as markers on both physical maps and genetic linkage maps. RFLPs are usually caused by mutation at a cutting site. See marker.
Retching
Dry vomiting.
Retrolisthesis
Posterior slippage of one vertebra onto another.
Retropulsion
The tendency to step backwards if bumped from the front or upon initiating walking; usually seen in patients who tend to lean backwards because of problems with balance.
Retrovirus
A family of RNA viruses that have the unique characteristic of producing an enzyme that makes a DNA copy of its genetic information from an RNA template (the opposite of what normally takes place). The most widely recognized of these viruses is HIV, the causative agent in AIDS. Another virus from this family (HTLV-1) has been associated with T cell leukemia. Initial reports of an association of an HTLV-II-like retrovirus with CFS could not be confirmed in subsequent studies.
Rheumatic fever
A childhood disease that may damage the heart valves or the outer lining of the heart.
Rhinitis
An inflammation of the mucous membrane that lines the nose; often due to allergy to pollen, dust, or other airborne substances; causes sneezing, itching, a runny nose, and nasal congestion.
Ribonucleic acid (RNA)
A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell. The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose.
Ribosomal RNA (RRNA)
A class of RNA found in the ribosomes of cells.
Ribosomes
Small cellular components composed of specialized ribosomal RNA and protein; site of protein synthesis. See ribonucleic acid (RNA).
RICE (REST, ICE, COMPRESSION, AND ELEVATION)
Treatment plan for acute injury to prevent inflammatory processes from becoming uncontrolled and to speed up the recovery process by eliminating swelling; acute injury management.
Rigidity
Increased resistance to the passive movement of a limb.
Risk factor
Activity or factor that may increase the chance of developing a disease.
Risk factor
Something that increases a person's chance of developing a disease.
RNA
Ribonucleic acid, a chemical similar to DNA. The several classes of RNA molecules play important roles in protein synthesis and other cell activities.
Roseola
Also known as roseola infantum, exanthem subitem, and pseudorubella. An acute disease of infants or very young children caused by HHV-6 and characterized by high fever and a skin rash.
Rotator cuff
Muscles and their insertional tendons that form a cuff over the shoulder joint, on their way to attaching from the scapula to the humorous; major function is to control, and produce, rotation of the shoulder.
Round window
Membrane separating the middle ear and inner ear.
Rubella
Also known as German measles, an acute disease marked by skin rash and swollen lymph nodes, but generally without fever. It is caused by an RNA virus of the togavirus family.
Rupture
Break or tear in any organ or soft tissue.
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