Biology of Disease

Systemic inflammatory response syndrome (SIRS) (see
superantigens).

Systole Contraction of the heart ventricles.

T lymphocytes These are derived fromsmall lymphocytes
that leave the bone marrow in an immature state and
mature intoTCorTHcellsin the fetal thymus.

Tachycardia An inappropriately fast heartbeat.

TCcells Blood cells that develop intocytotoxic T lym-
phocytes when appropriately stimulated, and which
are capable of killing virus-infected cells.

TH cells or helper T lymphocytes Blood cells that develop
into cytokine-secreting TH cells when stimulated
by animmunogen, and which produce an array of
cytokines that control the activities of cells of the
immune system.

Thalassemias A large group of related hemoglobinopa-
thies of varying severity that originate from point
mutations or deletions in globin genes.

Toxic diseases Diseases caused by the ingestion of a
variety of poisons that may be encountered in the
environment.

Toxicology The study of the adverse effects of toxic chem-
icals on organisms.

Transgenic organisms Organisms that express genes
from a different species that have been inserted into
their cells.

Traumatic diseases Diseases caused by physical injury
including mechanical trauma.

Tumor suppressor genes One of two major groups of
genes whose mutated forms are linked to the forma-
tion of cancers (compare withoncogenes).

Uricolysis The degradation of urate (uric acid) to CO 2 and
NH 3.

Vaccination The process of protecting people from infec-

tion by deliberately exposing them to parasite compo-

nents that initiate a protective immune response.

Vegetation An accumulation of bacteria and blood clots

on the valves of the heart.

Ventricle Lower chamber of the heart.

Virilism The development in females of inappropriate

male characteristics, for example hirsutism, increased

muscle mass, deepening of the voice and male psy-

chological characteristics.

Virulence factors Features ofpathogensthat allow them

to causeinfectious diseases.

Vitamers A term applied to a group of closely related

compounds that all posses the activity of the named

vitamin.

Vomiting or emesis The forced expulsion of food from

the stomach (and sometimes duodenum) through the

esophagus and mouth.

Winter depression Seeseasonally affective disorder.

Xanthomas Yellowish deposits on the tendons that occur

infamilial hypercholesterolemia.

Xenobiotic A substance that does not originate in the

body but is pharmacologically, endocrinologically or

toxicologically active.

Xenogeneic transplant The use of a graft from another

species (see alsoallograft).

Zoonoses Diseases that can be transmitted from animals

to humans.

Zymogens Precursor molecules that turn into active

proteases when subjected to a specific proteolytic

cleavage.

GLOSSARY

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