PRINCIPLES OF TOXICOLOGY

GLOSSARY 563
hemolytic anemia Anemia owing to shortened in vivo survival of mature red blood cells, and
inability of the bone marrow to compensate for their decreased life span.
hemoptysis The coughing or spitting up of blood from the respiratory tract.
hemorrhagic cystitis Urinary bladder inflammation compounded with bleeding.
hemosiderosis A general increase in iron stores in tissues without tissue damage.
hepatomegaly Enlargement of the liver.
hepatotoxin A toxin destructive of liver cells.
histamine A physiologically active amine, C5H9N3, found in plant and animal tissue. It is released
from cells of the immune system in human beings as part of an allergic reaction.
hives A skin condition characterized by intensely itching welts and caused by an allergic reaction to
internal or external agents, an infection, or a nervous condition. Also called urticaria.
homolog One of a series of compounds, each of which is formed from the one before it by the addition
of a constant element or a constant group of elements, as in the homologous series CNH2N+2,
compounds of which would be CH4, C2H6, C3H8, or similar.
humoral immunity The component of the immune response involving the transformation of B
lymphocytes into plasma cells that produce and secrete antibodies to a specific antigen.
hydrocarbon An organic compound consisting exclusively of the elements carbon and hydrogen.
Derived principally from vegetable sources, petroleum, and coal tar.
hydrolysis Decomposition of a chemical compound by reaction with water, such as the catalytic
conversion of starch to glucose.
hydrophilic Readily absorbing water; hygroscopic.
hydroxylation An oxidative reaction that introduces one or more hydroxyl groups into an organic
compound.
hyperalgesia A heightened or excessive sensitivity to pain.
hyperemia An excess of blood in some part of the body.
hyperkeratosis Overgrowth of the corneous layer of the skin, or any disease characterized by that
conditions.
hyperpigmentation Abnormally increased pigmentation.
hyperplasia Abnormal multiplication or increase in the number of normal cells in normal arrangement
in a tissue.
hypersensitivity A state of extreme sensitivity to an action of a chemical; for example, the individuals
of a test population who fit into the “low end” of an ED50 or LD50 curve (i.e., those individuals
who react to a very low dose as opposed to the median effective dose).
hypokinesis Abnormally decreased mobility; abnormally decreased motor function or activity.
hyposensitivity The state of decreased sensitivity; for example, the individuals of a test population
who fit into the “high end” of an ED50 or LD50 curve (i.e., those individuals who respond only to
a very high dose as compared to the median effective dose).
hypoxia A partial reduction in the oxygen concentration supplied to cells or tissues.
immune response See sensitization reaction.
incidence An expression of the rate at which a certain event occurs, as the number of new cases of
a specific disease occurring during a certain period.
inclusion body An abnormal structure in a cell nucleus or cytoplasm having characteristics staining
properties and associated especially with certain viral infections, such as rabies and smallpox.
infarct An area of necrosis in a tissue caused by local lack of blood resulting from obstruction of
circulation to the area.