Labile
Unstable or unsteady; not fixed; characterized by adaptability to
alteration or modification, i.e., relatively easily changed, as in
cleavage of a molecule or molecular rearrangement in a compound or
complex chemical material.
LAL (Limulus Amoebocyte Lysate)
A material obtained by rupturing the cellular components of the
blood of a horseshoe crab (Limulus Poliphemus). This material
coagulates in the presence of LPS (lypopolysaccharides) and is a
test used to quantitate bacterial endotoxins (pyrogens).
Laminar Airflow
(also see: Unidirectional Airflow)
Laminar Airflow - Clean Work Station
A workstation in which the unidirectional airflow characteristics
predominate throughout the entire airspace with a minimum of eddies
(turbulence) to jeopardize critical surfaces.
Laminar Flow
Non-turbulent fluid flow is usually considered laminar if the
Reynolds number is less than 2000 in a pipe. Depending upon many
possible varying conditions, the flow may be laminar at a Reynolds
number as low as 1,200 or as high as 40,000; however, such
conditions are not experienced in normal practice. In the
pharmaceutical industry, this term incorrectly refers to the air
discharge of a clean air bench or wall.
LAN (Local Area Network)
Networks with computers geographically close together (that is, in
the same building).
- Langelier Index
A measure of the degree of saturation of calcium carbonate in
water that is based on pH, alkalinity and hardness. If the
Langelier Index is negative, the water is corrosive (pH value
below 7 or acidic). If the Langelier Index is positive, calcium
carbonate can precipitate out of solution to form scale (pH value
above 7 or basic). The Langelier Index will vary for cold water
and for warm water.
Latent Heat
The amount of heat needed to change a unit of substance, such as
water, from a solid to a liquid without change in temperature or
pressure.
- Lay
In metallurgy, the direction of the predominant surface pattern
ordinarily determined by the production method used.
Leach
To dissolve by the action of a moving liquid. For example, high
purity water leaches trace impurities from glass vessels.
Legacy Systems
Hardware and software applications in which a company has already
invested considerable time and money. Legacy systems typically
perform critical operations in companies for many years even
though they may no longer use state-of-the-art technology.
Replacing legacy systems can be disruptive and therefore requires
careful planning and appropriate migration support from the
manufacturer.
LEL (Lower Explosive Limit)
Leptospira
A genus of the family Treponemataceae, thin coiled organisms,
flagellated at the extremities, one or both of which are bent back
like a hook. Both pathogenic and innocent forms have been
isolated.
Leukemia
Cancer that begins in developing blood cells in the bone marrow.
Leukocyte
A general name for white, nucleated blood cells found in the
blood and lymphatic tissue.
Level of Product Protection
The level of protection required for an area based on an
assessment by the manufacturer of contamination risk.
Ligand
A molecule or ion that is bound to protein.
Ligase
An enzyme used to catalyze the joining of single-stranded DNA
segments.
Linkage
The proximity of two or more markers (e.g., genes, RFLP markers)
on a chromosome; the closer together the markers are, the lower
the probability that they will be separated during DNA repair or
replication processes (binary fission in prokaryotes, mitosis or
meiosis in eukaryotes), and hence the greater the probability that
they will be inherited together.
Linkage Map
A map of the relative positions of genetic loci on a chromosome,
determined on the basis of how often the loci are inherited
together. Distance is measured in centimorgans (cM).
Lipids
Hydrophobic biological compounds (fats and fatlike materials)
that are insoluble in water, but soluble in nonpolar solvents such
as benzene, chloroform, and ether. The major components in most
lipids are fatty acids.
Lipoprotein
A conjugated protein containing a lipid, prosthetic group.
Liposome
An artificial phospholipid vesicle. Liposomes can be useful for
the enclosure of macromolecules such as nucleic acids or, after
loading with an appropriate drug. They may be used therapeutically
to achieve slow release of the drug into circulation.
Localize
Determination of the original position (locus) of a gene or other
marker on a chromosome.
- Locus (pl. loci) The position on a chromosome of a gene or
other chromosome marker; also, the DNA at that position. The use
of locus is sometimes restricted to mean regions of DNA that are
expressed.
- Long-Range Restriction Mapping
Restriction enzymes are proteins that cut DNA at precise
locations. Restriction maps depict the positions on chromosomes of
restriction enzyme cutting sites. These are used as biochemical "signposts",
or markers of specific areas along the chromosomes. The map will
detail the positions on the DNA molecule that are cut by
particular restriction enzymes.
Lot
Lot Number
Lou Gehrig's Disease
Lower Flammability Level (LFL)
The minimum concentration of vapor in air at which propagation of
flame will occur in the presence of an ignition source. LFL is
sometimes referred to as LEL or Lower Explosive Limit.
LPS (Lipopolysaccharide)
Molecule found in the outer cell walls of some bacteria that
trigger the immune response resulting in fever. Also referred to
as pyrogens or as endotoxins, though, strictly speaking, they are
not endotoxins but predominant components of endotoxins produced
by gram-negative bacteria. Common cause of pyrogenic reactions in
parenteral products.
Lymphocyte
A type of white blood cell accounting for 20-25% of the white
cells in humans. They are mostly non-phagocytic and actively
mobile and are continuously made in the bone marrow. They are the
immediate precursors of all antibody-forming cells.
Lyophilizer
A freeze dryer.
Lyophilization
Also known as freeze drying, it is a means of stabilizing wet
substances by freezing them, then evaporating the resulting ice,
to leave a substantially dry, porous residue which has the same
size and shape of the original frozen mass.
Lysate
A product of lysis, which is the disintegration or dissolution of
the cell walls.
Lysine
As essential, basic amino acid obtained from many proteins by
hydrolysis.
Lysis
The dissolution or destruction of red blood cells, bacteria, or
other antigens by a specific lysin (antibody), or by the action of
detergents, thus allowing the cell contents to escape.
Lysosome
A membrane-surrounded organelle in the cytoplasm of eukaryotic
cells; it contains many hydrolytic enzymes.
