App. H— Glossary of Acronyms and Terms • 427 
rules for its toxic substances and pesticides research 
programs. 
Guidelines for Animal Care and Use: Various or- 
ganizations outside the Federal Government have 
adopted their own guidelines— e.g., the APA’s Guide- 
lines for Ethical Conduct in the Care and Use of Ani- 
mals , which is the most comprehensive and has been 
endorsed by FASEB; the APS’s Guiding Principles in 
the Care and Use of Animals ; and the AVMA’s Ani- 
mal Welfare Guiding Principles. For Federal guide- 
lines, see Interagency Research Animal Committee, 
NIH Guide for the Care and Use of Laboratory Ani- 
mals, and PHS Policy. 
Hepatotoxicity: The quality of exerting a destructive 
or poisonous effect upon the liver. 
Homology: The correspondence among organisms of 
structures and functions derived from a common 
evolutionary origin (e.g., a common gene structure). 
Immunoscintigraphy: The use of external radioimag- 
ing techniques to locate tumors and to identify cer- 
tain noncancerous diseases. 
Institute for Laboratory Animal Resources (ILAR): 
A component of the National Research Council, ILAR 
performs periodic surveys on the use of laboratory 
animals. 
Interagency Research Animal Committee (IRAC): 
This committee was formed by 14 Federal entities 
in recognition of a need for an interagency body 
knowledgeable about the welfare of research ani- 
mals. IRAC meets regularly to discuss research needs 
and has written Principles for the Utilization and Care 
of Vertebrate Animals Used in Testing, Research and 
Training. These Principles, which incorporate nine 
injunctions on animal welfare, are intended to serve 
as a model for Federal agencies in developing pol- 
icies on animal use. 
Invertebrate: Any nonplant organism without a spinal 
column— e.g., worms, insects, and crustaceans. In- 
vertebrates account for 90 percent of the Earth’s non- 
plant species. For the purposes of this assessment, 
invertebrates are not considered to be animals. 
In vitro: Literally, in glass; pertaining to a biological 
process or reaction taking place in an artificial envi- 
ronment, usually a laboratory. Human and animal 
cells, tissues, and organs can be cultured in vitro. 
In vitro testing may hold some promising alterna- 
tives to animal testing— e.g., in testing for eye irrita- 
tion and mutagenicity. 
In vivo: Literally, in the living; pertaining to a biologi- 
cal process or reaction taking place in a living cell 
or organism. 
Laboratory Animal Data Bank (LADB): Founded by 
NCI and NLM in the late 1970s, the LADB was sup- 
posed to provide a computer-based registry of re- 
search and testing data. However, the data were 
limited and consequently LADB had few users. It was 
terminated in 1981 because of lack of funding. It ex- 
ists today only as an archival reference. 
LC 50 :An acute toxicity test used to screen substances 
for their relative toxicity. LC S0 is calculated to be the 
lethal concentration for half of the animals exposed 
to a test substance. Exposure may be by breathing 
vapor or immersion in liquid (e.g., fish in water). 
LD 50 : An acute toxicity test used to screen substances 
for their relative toxicity . LD S0 is calculated to be the 
lethal dose for half of the animals exposed to a test 
substance. Exposure is often by ingestion. 
Mechanistic Toxicology: An approach to testing that 
focuses on the chemical processes by which a toxic 
effect occurs. Mechanistic toxicology testing relies 
heavily on physiology, biochemistry, and analytical 
chemistry techniques to monitor these processes. 
Micro-organism: A minute microscopic or submicro- 
scopic living organism, such as bacteria, viruses, and 
protozoa. 
Mutagen: An agent that induces chemical changes in 
genetic material. Chemicals, viruses, and ionizing 
radiation can be mutagenic. Most carcinogens are 
mutagens, therefore many screening tests to detect 
carcinogens are designed to detect the mutagenic 
potential of the compound. Some mutagens are not 
direct-acting, requiring metabolic activation in the 
body before they exert their mutagenic potential. 
National Toxicology Program (NTP): NTP was char- 
tered in 1978 as a cooperative effort by DHHS. Par- 
ticipants in NTP are NIH (through its agencies NCI 
and NIEHS), FDA (through NCTR), and CDC (through 
NIOSH). The stated goals of NTP include the expan- 
sion of toxicological information; expansion of num- 
bers of chemicals to be tested; the validation, devel- 
opment, and coordination of tests to meet regulatory 
needs; and the communication of programs, plans, 
and results to the public. 
Neurotoxicity: The quality of exerting a destructive 
or poisonous effect on nerve tissue. 
NIH Guide for the Care and Use ofLabora tory A ni- 
mals : Revised in 1985, the Guide lays out detailed 
standards for animal care, maintenance, and hous- 
ing. Its provisions apply to all research supported 
by NIH, and it is used by most animal research facil- 
ities, both within and outside the Federal Govern- 
ment. AAALAC and PHS also use it when assessing 
research facilities for accreditation. 
Nonliving Systems: Inanimate chemical or physical 
systems used in testing. 
Oncology: The study of tumors. 
