Medications

Helmet, bicycle: A well-known but often neglected device designed to protect the head of a bicyclist. Helmets decrease the risk of head injuries (traumatic brain damage) by about 85%. Unfortunately, only about 18% of bicyclists in the US use helmets...

HELLP syndrome - Medical

HELLP syndrome: A syndrome featuring a combination of "H" for hemolysis (the breakdown of red blood cells), "EL" for elevated liver enzymes, and "LP" for low platelet count (an essential blood clotting element). The HELLP syndrome is a recogn...

Helix, double - Medical

Helix, double: The structure of DNA with the two strands of DNA spiraling about one other. The double helix looks something like an immensely long ladder twisted into a helix, or coil. The sides of the "ladder" are formed by a backbone of sugar and...

Helix, alpha - Medical

Helix, alpha: See: Alpha helix.Last Editorial Review: 10/19/2003 Alpha helix: The coiled structure of many proteins consisting of a single chain of amino acids stabilized by hydrogen bonds. The alpha helix was first proposed by Linus Pauling and Rob...

Helicobacter pylori - Medical

Helicobacter pylori: Bacteria that cause stomach inflammation (gastritis) and ulcers in the stomach. This bacteria is the most common cause of ulcers worldwide. It is often referred to as H. pylori. H. pylori infection is usually acquired fro...

Helicobacter heilmannii - Medical

Helicobacter heilmannii: A bacteria that infects most cats, dogs and pigs and, in them, causes stomach inflammation (gastritis). H. heilmannii is not usually transmitted from animals to people. But people who have been infected by H. heilmannii a...

Helicase - Medical

Helicase: An enzyme that unwinds double-strand DNA into two single DNA strands. Last Editorial Review: 8/18/2003...

Helical CAT scan - Medical

Helical CAT scan: A conventional computerized axial tomography scan (CAT scan or CT scan) is an x-ray procedure which combines many x-ray images with the aid of a computer to generate cross-sectional views and, if needed, three-dimensional images of ...

HeLa cell - Medical

HeLa cell: One of the cells grown from the cervical cancer of a young African-American woman, Henrietta Lacks. HeLa cells were the first human cells to be continuously grown in culture. The cells were first cultured in February 1951 by Drs. Georg...

Heimlich maneuver - Medical

Heimlich maneuver: An emergency treatment for obstruction of the airway in adults. It may be needed when someone chokes on a piece of food that has "gone down the wrong way." To perform the Heimlich maneuver, stand behind the victim, wrap your ar...

Heights, fear of - Medical

Heights, fear of: An irrational unreasonable fear of heights is called acrophobia. From the Greek "acron", height + "phobos", fear.Last Editorial Review: 7/20/1999 8:35:00 PM...

Height growth - Medical

Height growth: See: Normal growth.Last Editorial Review: 6/27/2004 Normal growth rate: The speed with which normal growth occurs in length before birth and in height after birth. Fetal growth is critical to a person's eventual height. Before birth...

Heel stick - Medical

Heel stick: A procedure in which a newborn baby's heel is pricked and then a small amount of the blood is collected, usually with a narrow-gauge ("capillary") glass tube or a filter paper. The heel stick is now the most common way to draw blood from...

Heel spur - Medical

Heel spur: A bony spur projecting from the back or underside of the heel that often makes walking painful. Spurs at the back of the heel are associated with inflammation of the Achilles tendon (Achilles tendinitis) and cause tenderness and pa...

Heel prick - Medical

Heel prick: A procedure in which the heel is pricked and then a small amount of the blood is collected, usually with a narrow-gauge ("capillary") glass tube or a filter paper. The heel prick is now the most common way to draw blood from newborns. B...

Heel bone - Medical

Heel bone: Formally called the calcaneus. A more or less rectangular bone at the back of the foot. The words "calcaneus" and "calcium" come from the same source. Last Editorial Review: 4/27/2011 5:27:15 PM...

Heebie-jeebies - Medical

Heebie-jeebies: Extreme nervousness. A term coined by the America cartoonist Billy DeBeck (1890-1942) in his comic strip Barney Google.Last Editorial Review: 5/31/2004...

Hedonophobia - Medical

Hedonophobia: An abnormal, excessive, and persistent fear of pleasure. Sufferers with this most puritanical of phobias typically feel guilty about experiencing pleasure even though they usually realize rationally there is nothing at all wrong with ta...

Hecht-Beals syndrome - Medical

Hecht-Beals syndrome: See: Hecht syndrome. Last Editorial Review: 7/28/2004 Hecht syndrome: A striking genetic disorder in which abnormally short muscles in the jaw make it impossible to open the mouth fully (trismus) and abnormally short muscles i...

Hecht's pneumonia - Medical

Hecht's pneumonia: Also known as giant cell pneumonia, this is a deadly but fortunately rare complication of measles. It tends to strike children who are immunodeficient as from leukemia or HIV/AIDS. The postmortem examination (autopsy) shows multi...

Hecht syndrome - Medical

Hecht syndrome: A striking genetic disorder in which abnormally short muscles in the jaw make it impossible to open the mouth fully (trismus) and abnormally short muscles in the hands keep the fingers straight when the hand is flexed back (pseudocamp...

Heberden node - Medical

Heberden node: A small fixed bump on the finger, usually at the last joint of the finger, Heberden's node is a calcified spur of the joint (articular) cartilage and is a sign of osteoarthritis. Named for the English physician William Heberd...

Heberden disease - Medical

Heberden disease: There are two different Heberden diseases: Angina pectoris, chest pain that is often severe and crushing, due to an inadequate supply of oxygen to the heart muscle. Osteoarthritis of the small joints with nodules (Heberden ...

Heatliness - Medical

Heatliness: A characteristic of certain foods or other substances believed to cause emotional or physical reactions associated with temper, fever, passion, and excess. Coolness and heatliness are the yin and yang of a principle of Chinese philosoph...

Heat-related illness - Medical

Heat-related illness: A person with symptoms including headache, nausea, and fatigue after exposure to heat probably has some measure of a heat-related illness. It is important to recognize the difference between the very serious condition known as ...

Heat syncope - Medical

Heat syncope: Sudden dizziness, feeling faint ans sometimes fainting experienced after exercising in the heat. The skin appears pale and sweaty but is generally moist and cool. The pulse may be weakened, and the heart rate is usually rapid. Body tem...

Heat stroke - Medical

Heat stroke: A core body temperature that rises above 104 F (40 C) accompanied by hot, dry skin and central nervous system abnormalities such as delirium, convulsions, or coma. Heat stroke that results from exposure to a high environmental temperatu...

Heat rash (Pictures) - Medical

Heat rash: Heat rash is an irritation of the skin that results from excessive sweating during hot and humid weather. Heat rash appears as clusters of red pimples or blisters on the skin. It is more likely to occur on the neck and upper chest, i...

Heat prostration - Medical

Heat prostration: Overheating of the body due to extreme weather conditions. Unrelieved hyperthermia can lead to collapse and death, particularly in the elderly. Prevention via air conditioning, ventilation, and drinking extra water is the ke...

Heat index - Medical

Heat index: The temperature the body feels when heat and humidity are combined. The body dissipates heat by varying the rate and depth of blood circulation, by losing water through the skin and sweat glands, and as a last resort, by panting, when blo...