The most plentiful element in the universe and one present in all organic compounds. Hydrogen is a gas with an atomic number of 1 and the symbol H.
Two isotopes of hydrogen — deuterium and tritium — have been used as tracers in metabolic studies. Tritium is a long-lived weak emitter of radiation and can be easily incorporated in large molecules such as DNA, and is therefore much used for autoradiography in the laboratory.
Antoine Lavoisier coined the name hydrogen from the Greek hydro (water) + genes (forming), reflecting the fact that water is generated by the combustion of this element.
Distention of the kidney with urine. Hydronephrosis is caused by obstruction of urine outflow (for example, by a stone blocking the ureter).
1. Literally, an irrational fear of water, to drink or to swim in. Someone who is scared of the water is hydrophobic. 2. A term once commonly used for rabies because in the later stages of that disease, the animal (or person) has difficulty swallowing and so fears a drink of water. From hydro-, water […]
- Hydrops fetalis
Gross edema (swelling), usually with anemia, of the fetus. It can be due to Rh blood group incompatibility, in which antibodies crossing the placenta from the mother destroy the red blood cells of the fetus. It can also be caused by a lethal form of the genetic disorder thalassemia, alpha thalassemia, in which alpha-chain polypeptides […]
A major component and an essential ingredient of normal bone and teeth. Hydroxyapatite makes up bone mineral and the matrix of teeth. It is hydroxyapatite that gives bones and teeth their rigidity. Hydroxyapatite molecules can group together (crystalize) to form microscopic clumps. If these tiny crystals of hydroxyapatite are deposited by mistake in or around […]
- Hydroxyapatite crystal disease
Inflammation caused by hydroxyapatite crystals. Hydroxyapatite molecules can group together (crystallize) to form microscopic clumps. If the tiny crystals of hydroxyapatite are deposited by mistake in or around joints, they may cause inflammation of the joints and nearby tissues, such as tendons and ligaments. Hydroxyapatite crystal disease is sometimes the cause of rotator cuff problems […]