IUPAC Glossary of Terms Used in Toxicology – Terms Starting with L
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lachrymation
See lacrimation
lacrimation
Secretion and discharge of tears.
lachrymator
See lacrimator
lacrimator
Substance that irritates the eyes and causes the production of
tears or increases the flow of tears.
larvicide
Substance intended to kill larvae.
laryngospasm
Reflex spasmodic closure of the sphincter of the larynx, particularly the glottic
sphincter.
larynx
Main organ of voice production, the part of the respiratory tract
between the pharynx and the trachea.
lassitude
Weakness; exhaustion.
latency
See latent period
latent effect
See delayed
effect
- Delay between exposure to a harmful substance and the manifestations of a disease or other adverse effects.
- Period from disease initiation to disease detection.
[2]
lavage
Irrigation or washing out of a hollow organ or cavity such as the
stomach, intestine or the lungs.
laxative
cathartic
purgative
Substance that causes evacuation of the intestinal contents.
lead colic (painters’
colic)
Chronic intestinal pains and constipation caused by lead
poisoning.
lesion
- Area of pathologically altered tissue.
- Injury or wound.
- Infected patch of skin.
lethal
Deadly; fatal; causing death.
lethal concentration
(LC)
Concentration
of a substance in an environmental medium that causes death
following a certain period of exposure.
lethal dose (LD)
Amount of a substance or physical agent (e.g. radiation) that
causes death when taken into the body.
lethal synthesis
Metabolic formation of a highly toxic compound
often leading to death of affected cells.
leukemia
Progressive, malignant
disease of the blood-forming organs, characterized by distorted
proliferation and development of leucocytes and their precursors
in the bone marrow and blood.
leukopenia
Reduced concentration
of leukocytes in the blood.
See lgPow
lgKow
Logarithm to the base 10 of the partition coefficient of a
substance between octan-1-ol and water.
Note: This is used as an empirical measure for lipophilicity in
calculating bioaccumulation, fish toxicity,
membrane adsorption and penetration etc.
library (in DNA
bio-informatics)
Collection of DNA sequences in a searchable electronic form.
library (in molecular biology)
Collection of genomic or complementary DNA sequences that have
been cloned in a vector and grown in an appropriate host organism
(e.g. bacteria, yeast).
After [9]
life-long exposure
Subjection to a potentially toxic substance
during the whole lifetime.
ligand
Ion, molecule, or molecular group that binds to another chemical entity to form a larger complex.
limacide
Substance intended to kill mollusks including the gastropod
mollusk, Limax.
limit recommended
See recommended exposure limit
limit test
Acute toxicity test
in which, if no ill-effects occur at a pre-selected maximum dose,
no further testing at greater exposure levels
is required.
limit value (LV)
Limit concentration
at or below which Member States of the European Community must
set their environmental
quality standard and emission
standard for a particular substance according to
Community Directives.
limited evidence
According to the US EPA's guidelines for Carcinogen Risk Assessment,
“limited evidence” is a collection of facts and
accepted scientific inferences that suggests that an agent may be
causing an effect, but this suggestion is not strong enough to be
considered established fact.
linearized multistage
model
Sequence of steps in which (a) a multistage
model is fitted to tumor incidence
data; (b) the maximum linear term consistent with the data is
calculated; (c) the low-dose slope of
the dose-response function is equated
to the coefficient of the maximum linear term; and (d) the
resulting slope is then equated to the upper bound of
potency.
lipophilic/ adj., -ity
n.
hydrophobic/ adj., -ty n.
antonyms hydrophilic/
-ity, lipophobic/
-ity
Having an affinity for fat and high lipid solubility.
Note: This is a physicochemical property which describes a
partitioning equilibrium of solute molecules between water and an
immiscible organic solvent, favoring the latter, and which
correlates with bioaccumulation.
lipophobic/ adj., -ity
n.
hydrophilic/ adj., -ity n.
antonyms hydrophobic/
adj. ity
n., lipophilic/
adj. ity n.
Having a low affinity for fat and a high affinity for water.
liposome
- Artificially formed lipid droplet, small enough to form a relatively stable suspension in aqueous media, useful in membrane transport studies and in drug delivery.
- Lipid droplet in the endoplasmic reticulum of a fatty
liver.
After [1]
local effect
Change occurring at the site of contact between an organism and a
toxicant.
logit
In competitive binding assays, the logit-log dose
relationship, in which the response is
defined by:
R = logit (y) = lg [y/(1 –
y)]
where y = b/b0 with
b = fraction of tracer bound and b0
= value of b with no unlabelled ligand in the
system.
Note: Logit-transformed assay data frequently yield straight-line
dose-response data, amenable to statistical analysis. More
generally in toxicology, the transformation is applied to
dose-response data where b0 denotes the
maximum response in the absence of a toxic substance.
[2]
log-normal distribution
Distribution
function F(y), in which the logarithm of a
quantity is normally distributed, i.e.
F(y) = ƒgauss(ln y)
where ƒgauss(χ) is a Gaussian (or
normal) distribution.
[3]
log-normal
transformation
Transformation of data with a logarithmic function that results
in a normal distribution.
[2]
long-term effect
See chronic
effect
long-term exposure
See chronic
exposure
long-term toxicity
See chronic
toxicity
lowest effective dose
(LED)
Lowest dose of a chemical inducing a
specified effect in a specified fraction of exposed
individuals.
[2]
lowest lethal concentration
found
See minimum
lethal concentration
lowest-observed-adverse-effect level
(LOAEL)
Lowest concentration
or amount of a substance (dose),
found by experiment or observation, which causes an adverse
effect on morphology, functional capacity, growth,
development, or life span of a target organism
distinguishable from normal (control) organisms of the same
species and strain under defined conditions of exposure.
lowest-observed-effect level
(LOEL)
Lowest concentration
or amount of a substance (dose),
found by experiment or observation, that causes any alteration in
morphology, functional capacity, growth, development, or life
span of target organisms
distinguishable from normal (control) organisms of the same
species and strain under the same defined conditions of
exposure.
lymphocyte
Animal cell that interacts with a foreign substance or organism,
or one which it identifies as foreign, and initiates an immune
response against the substance or organism.
Note: There are two main groups of lymphocytes, B lymphocytes and
T lymphocytes.
lymphoma
General term comprising tumors and
conditions allied to tumors arising from some or all of the cells
of lymphoid tissue.
lysimeter
Laboratory column of selected representative soil or a protected
monolith of undisturbed field soil with which it is possible to
sample and
monitor the movement of water and substances.
lysosome
Membrane-bound cytoplasmic organelle containing hydrolytic
enzymes.
Note: Release of these enzymes from lysosomes damaged by
xenobiotics can cause autolysis of the cell.