Glossary of Terms - e

Index

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Terms

Echocardiography: A noninvasive procedure that utilizes reflected ultrasonic waves (echoes) directed to the heart that are converted and recorded as an image showing internal structures. It is used to study the heart structure and motion in diagnosis of pathologic cardiovascular changes.
Ejaculation: A sudden release of fluid, especially of semen, from the body.
Electroblot tests: A number of diagnostic transfer methods (blots) which allow shifting of proteins from gels to cellulose, where they are isolated and immobilized and can be detected and identified by a variety of techniques. The cellulose soaks up proteins like a blotter.
Electrocardiogram (ECG or EKG): A graphic recording that shows electrical activity generated by the heart muscle. It is used to help diagnose specific cardiac anomalies. such as disturbances of heart rhythm and conduction.
Electrocardiograph: The instrument used to detect and record the electrical activity of the heart muscle. It produces the ECG.
Electroencephalogram (EEG): A chart that provides a record of the electrical activity of the brain. which is derived from electrodes placed on the scalp. The instrument used is an electroencephalograph. An electroencephalogram is useful in diagnosis of seizure disorders and tumor detection.
Electrolyte: A solution of a compound that dissociates into ions and can conduct electricity. Electrolytes affect the movement of substances between body fluids and tissues, and are crucial for normal function and metabolism. In many illnesses, monitoring proper balance among the most important ones is vital. Calcium and potassium, for example, are necessary for cardiac and skeletal contractions and relaxations, and sodium is essential for fluid balance. An electrolyte imbalance can be caused by disease conditions or medications. Electrolytes also are used as electrical conductors in electrophoretic test methods.
Electron microscope: An electron-optical instrument that utilizes a beam of electrons, rather than light, to focus on cell surfaces of a very thin specimen to produce an enlarged image on a fluorescent screen or photographic plate. Because resolution (the ability to distinguish adjacent objects as separate) is better and magnification 1,000 times that of an optical light microscope is possible, electron microscopy can help determine the nature of tumors and of kidney disease. See scanning electron microscope.
Electronic fetal monitoring: The use of external and internal devices that record the fetal heart rate. An externally applied ultrasound transducer converts sound energy into electrical energy which is recorded on a graph. After rupture of the membranes, an electrode can be applied via the maternal vagina to the fetal scalp to obtain a fetal ECG. The maternal uterine contractions also are recorded on the graph so that they can be related to the fetal heart rate, to indicate fetal distress.
Electrophoresis: Movement of charged particles in an electrical field, a technique used to separate materials in a substance by placing a sample in a buffer solution through which an electrical current then is passed. Extent of migration and separation of components depends on molecular weight and electrical charge of the particles. This method often is used to determine the proportions of various proteins in serum.
Enzyme: A protein produced by cells that influences the speed of a specific chemical reaction without being used up or permanently changed in the process. Enzymes are catalysts.
Enzyme immunoassay (EIA): An assay that uses an enzyme-bound antibody to detect antigen. The enzyme catalyzes a color reaction when exposed to substrate.
Enzyme-linked fluorescent assay (ELFA): Similar to EIA except the enzyme catalyzes a fluorescence, not a color reaction.
Enzyme-linked immunosorbent assay (ELISA): See assay.
Estrogen: A female sex hormone.
Ethanol: Ethyl alcohol, the type used in alcoholic beverages, medicines, and food products. Blood levels of ethanol can be ascertained by tests that indicate the degree of intoxication. Alcohol affects brain function (central nervous system depressant) and may produce chronic illness in susceptible individuals.
Euthyroidism: A normal thyroid hormone status most precisely defined by a normal TSH level.