Biotechnology

Endocrinology The branch of science that
studies the endocrine glands, hormones, and
hormone-like substances. See also 
ENDOCRINE
GLANDS
,
HORMONE
,
ENDOCRINE HORMONES
.
Endocytosis Also called receptor-mediated
endocytosis. The import of substances (e.g.,
hormones, viruses, and toxins) into a cell via
specific receptor/ligand binding. The entity
under consideration binds to a receptor(s)
located in the plasma (cell) membrane,
which then invaginates (infolds), hence tak-
ing up the entity via “endosomes” (formed
by pinching off an infold to form a “bag”)
into vesicles located within the cell. It is one
route to deliver essential metabolites to cells
(e.g., low-density lipoprotein), and it is a
means to modulate the cell’s responses to
many protein hormones and growth factors
(e.g., insulin, epidermal growth factor, and
nerve growth factor).
It is a route by which certain proteins
targeted for destruction can be taken up and
delivered to the cell’s lysosomes. For example,
© 2002 by CRC Press LLC

E
phagocytic cells have receptors enabling
them to take up antigen-antibody complexes
for subsequent destruction by the phagocytic
cell. This route is also a means exploited by
certain viruses and toxins to gain entry into
cells through the otherwise impervious cell
membranes (e.g., used by the AIDS virus
and the Semliki Forest Virus). Disorders of
endocytosis can lead to disease states (e.g.,
high cholesterol levels in the blood of people
whose low-density lipoprotein receptors are
impaired). Drugs (e.g., certain painkillers)
can be targeted to specific receptors via
receptor mapping (RM) and receptor fitting
(RF) for greater efficacy. See also 
INVASIN
,
ADHESION MOLECULE
,
CD
4
PROTEIN
,
EXOCYTOSIS
,
T CELL RECEPTORS
,
SIGNAL TRANSDUCTION
,
VAG-
INOSIS
,
RECEPTORS
,
RECEPTOR FITTING
  (
RF
),
HIGH
-
DENSITY LIPOPROTEINS
 (
HDLP
s
),
LOW
-
DEN-
SITY LIPOPROTEINS
  (
LDLP
s
),
RECEPTOR MAPPING
(
RM
),
SIGNALING
,
NUCLEAR RECEPTORS
.
Endodermal Adult Stem Cells Certain stem
cells present within (adult) bodies of organ-
isms, that can be differentiated (via chemical
signals) to give rise to cells of tongue, ton-
sils, the bladder/urethra, digestive tract, liver,
pancreas, lung tissues, etc. See also 
STEM
CELLS
,
MULTIPOTENT ADULT STEM CELLS
,
CELL
,
ORGANISM
,
SIGNALING
.
Endoglycosidase An enzyme capable of
hydrolyzing (breaking) interior bonds in the
oligosaccharide molecular branches of a gly-
coprotein molecule. That is, the enzyme is
capable of cutting a sugar-to-sugar bond
anywhere within the sugar polymer mole-
cule (depending, of course, on the specificity
of the enzyme). This is in contrast to an
exoglycosidase, which must cut away at the
polymer from the outside, i.e., from the free
end, one unit (or section, as the case may
be) at a time. See also 
EXOGLYCOSIDASE
,
GLYCOPROTEIN
,
ENZYME
,
OLIGOSACCHARIDES
,
RESTRICTION ENDOGLYCOSIDASES
,
HYDROXYLA-
TION REACTION
.
Endometrium The lining of the uterus.
Endonucleases A class of enzymes capable of
hydrolyzing (breaking) the interior phos-
phodiester bonds of DNA or RNA chains.
As opposed to cleavage (by exonucleases) at
the terminal bonds (ends) of a chain. See
also
ENZYME
,
DN
ase 1
,
DN
ase 2
,
EXONUCLEASE
,
ENDOGLYCOSIDASE
.
Endophyte A microrganism (fungus or bacte-
rium) that lives inside vascular tissues of
plants (in spaces between plant cells). At least
one company has incorporated the gene for a
protein toxic to insects (taken from Bacillus
thuringiensis) into an endophyte to confer
insect resistance to a crop plant. When endo-
phyte-infested fescue grass is fed to cattle,
sheep, horses, or rabbits, it is generally toxic
to those animals, due to mycotoxin(s) or alka-
loids produced by that endophyte. See also
MICROORGANISM
,
BACTERIA
,
BACILLUS THURING-
IENSIS
  (
B
.
t
.),
FUNGUS
,
PROTEIN
,
MYCOTOXINS
,
TREMORGENIC INDOLE ALKALOIDS
.
Endoplasmic Reticulum (ER) A highly spe-
cialized, complex network of branching,
intercommunicating tubules (surrounded by
membranes) found in the cytoplasm of most
animal and plant cells. The two types of ER
recognized are: rough ER and smooth ER.
Rough ER is covered with many ribosomes;
ER without or with fewer ribosomes
attached is called smooth. This nomencla-
ture comes about because of the appearance
of the ER under high magnification. The
rough ER is very well developed to facilitate
cells carrying on abundant protein synthesis,
because proteins are synthesized (manufac-
tured) in ribosomes. See also 
CELL
,
CYTOPLASM
,
RIBOSOMES
,
FATS
,
LIPIDS
,
PLASMA MEMBRANE
,
PROTEIN
,
PHOSPHOLIPIDS
.
Endorphins Discovered during the 1970s by
U.S. and Scottish scientists, these hormones
are produced in the brain, and act as natural
painkillers. For example, runners and long-
distance walkers achieve something of a
“high” due to endorphins released during
long runs or walks. See also 
ENKEPHALINS
,
CATECHOLAMINES
,
HORMONE
.
Endosome See
ENDOCYTOSIS
.
Endosperm The interior portion of a plant
seed, beneath the outer hull (the portion that
people tend to eat, in food crops). In grains
(e.g., rice or corn/maize), the endosperm
consists primarily of starch (carbohydrate).
In legumes (e.g., beans), the endosperm con-
tains mainly protein, a small amount of car-
bohydrates, and sometimes vegetable oil.
See also 
STARCH
,
CORN
,
SOYBEAN PLANT
,
© 2002 by CRC Press LLC

E
CARBOHYDRATES
  (
SACCHARIDES
),
SOYBEAN OIL
,
ALEURONE
.
Endospore A highly resistant, dormant inclu-
sion body formed within certain bacteria. To
kill spores, temperatures above boiling are
usually needed. For this, pressure cookers
and autoclaves are required. Endospores have
survival value since the spore can remain for
long periods of time in a nongrowing state
and then, under appropriate conditions, can
be induced to germinate and regenerate the
original cell. Endospore formation may be
viewed as being akin to hibernation, i.e., a
kind of “bacterial hibernation.”
Endostatin An antiangiogenesis human pro-
tein discovered by Judah Folkman. In con-
cert with angiostatin, it causes certain cancer
tumors in mice to shrink. See also 
PROTEIN
,
ANTIANGIOGENESIS
,
ANGIOSTATIN
,
CANCER
.
Endothelial Cells These are the flat, sort of
plate-shaped cells that line the surface of all
blood vessels, heart, and lymphatics within
the body. Endothelial cells possess trans-
membrane (through the cell membrane)
molecules known as adhesion molecules,
which selectively allow the passage (from
bloodstream to tissues) of some molecules
(leukocytes, monocytes, hormones, etc.).
Endothelial cells are packed much tighter
together in the capillaries that provide blood
to the brain. This tighter packing limits the
size and kind of molecules that can pass into
the brain. This blood-brain barrier serves to
protect the sensitive brain tissue from patho-
gens or harmful molecules (e.g., toxins). See
also
ENDOTHELIUM
,
VASCULAR ENDOTHELIAL
GROWTH FACTOR
 (
VEGF
),
ADHESION MOLECULES
,
MONOCYTES
,
MITOGEN
,
SELECTINS
,
BLOOD
-
BRAIN
BARRIER
 (
BBB
),
LECTINS
,
ELAM
-1
,
ATP SYNTHASE
,
OXIDATIVE STRESS
,
CYCLOOXYGENASE
.
Endothelin A peptide that causes arteries to
contract (which consequently causes blood
pressure to increase). See also 
PEPTIDE
,
ATRIAL PEPTIDES
.
Endothelium The layer of epithelial cells that
line blood vessels throughout the body. The
layer selectively allows the passage (from
bloodstream to tissues) of nutrients, hor-
mones, and other molecules essential for tis-
sue growth and function. The endothelium
is involved in the recovery and recycling of
old red blood cells. It also produces nitric
oxide, which causes neighboring smooth-
muscle (blood vessel) cells to relax so that
those (neighboring ) blood vessels dilate and
the body’s blood pressure is lowered, and two
compounds, prostacyclin and Von Willebrand
factor, that prevent blood clotting. See also
ENDOTHELIAL CELLS
,
VASCULAR ENDOTHELIAL
GROWTH FACTOR
  (
VEGF
),
SELECTINS
,
LECTINS
,
ADHESION MOLECULES
,
NITRIC OXIDE
,
NITRIC
OXIDE SYNTHASE
,
BILIRUBIN
.
Endotoxin A lipopolysaccharide (fat/sugar
complex; poison, also known as LPS) which
forms an integral part of the cell wall of gram
negative bacteria. It is only released when
the cell is ruptured. It can cause, among
other things, septic shock and tissue damage.
Pharmaceutical preparations are routinely
tested for the presence of endotoxins. This
is one reason why pharmaceuticals must be
prepared in a sterile environment. See also
SEPSIS
,
BACTERIA
,
LIPIDS
,
POLYSACCHARIDES
,
TOXIN
,
CHOLERA TOXIN
,
GRAM
-
NEGATIVE
  (
G-
),
GOOD MANUFACTURING PRACTICES
 (
GMP
).
Engineered Antibodies Chimeric monoclonal
antibodies, produced via genetic engineering
of human antibody-producing cells (clones).
For example, the genes coding for antilym-
phoma binding sites from a rat have been
inserted into human antibody-producing
cells to yield rat (antigen) binding sites
mounted on human antibody “stems." See
also
CHIMERIC PROTEINS
,
MONOCLONAL ANTI-
BODIES
 (
MA
b
),
ANTIBODY
,
GENETIC ENGINEERING
,
COMBINING SITE
,
LYMPHOCYTE
,
SEMISYNTHETIC
CATALYTIC ANTIBODY
.
Enhanced Nutrition Crops See
NUTRIENT
ENHANCED
™
.
Enkephalins A class of hormones produced in
the brain that act as natural painkillers. Dis-
covered by John Hughes and Hans Kosterlitz
in 1975, they are some of the endorphins.
See also 
ENDORPHINS
.
Enolpiruvil Shikimate See
EPSP SYNTHASE
.
Enolpyruvil Shikimate See
EPSP SYNTHASE
.
Enoyl-acyl Protein Reductase A n   e n z y m e
that is utilized by bacteria in their synthesis
(manufacture) of fatty acids. See also 
ENZYME
,
PROTEIN
,
BACTERIA
,
FATTY ACID
,
ESSENTIAL
FATTY ACIDS
.
© 2002 by CRC Press LLC

E
Ensiling The fermentation of (usually chopped
up) agricultural vegetation in order to pre-
serve it. It is carried out for 1–2 weeks, using
either indigenous microorganisms (e.g.,
Lactobacillus spp.) or introduced micro-
organisms (to speed up the process, yield
product containing more nutrients for live-
stock, etc.), in the absence of oxygen (to
prevent the growth of aerobic mold fungi).
When indigenous microorganisms are used,
Lactobacillus spp. become the dominant
microorganisms present, and heat is generated
by the microorganisms within the vegetative
mass (optimum temperature is 25–30°C,
which is 77–86°F). Lactic acid produced by
the microorganisms inhibits the growth of
bacteria that would normally putrefy the veg-
etation. See also 
FERMENTATION
,
MICROORGAN-
ISM
,
AEROBIC
,
FUNGUS
,
OPTIMUM TEMPERATURE
.
Enterohemorrhagic E. coli The several dozen
(approximately 60 known) serotypes
(strains) of E. coli bacteria that cause inter-
nal hemorrhaging in humans that ingest
those bacteria. The toxin produced by these
particular E. coli bacteria attacks the human
kidney, which often leads to kidney failure
and/or death. See also 
ESCHERICHIA COLIFORM
0157
:
H
7
  (
E
.
COLI
0157
:
H
7
),
TOXIN
,
SEROTYPES
,
ENTEROTOXIN
.
Enterotoxin The category (i.e., intestinally
active) of toxins, produced by certain bacte-
rial strains and/or serotypes, which attack
the body’s internal organs. For example, the
serotype of Escherichia coliform bacteria
known as E. coli 0157:H7 attacks the kid-
neys and other internal organs of humans,
also causing internal bleeding and some-
times death. See also 
TOXIN
,
BACTERIA
,
E S C H E R I C H I A
C O L I F O R M
0 1 5 7
:
H
7
,
E N T E R -
PHEMORHAGIC E
.
COLI
,
SEROTYPES
,
CHOLERA
TOXIN
.
Enzyme An organic, protein-based catalyst
that is not itself used up in the reaction. It is
naturally produced by living cells to catalyze
biochemical reactions. Each enzyme is
highly specific with regard to the type of
chemical reaction that it catalyzes, and to the
substances (called substrates) upon which it
acts. This specific catalytic activity and its
control by other biochemical constituents are
of primary importance in the physiological
functions of all organisms. Although all
enzymes are proteins, they may, and usually
do, contain additional nonprotein compo-
nents called coenzymes that are essential for
catalytic activity. See also 
APOENZYME
,
CATA-
LYST
,
COENZYME
,
HOLOENZYME
,
SUBSTRATE
(
CHEMICAL
),
PROTEIN
,
HORMONE
,
EXTREMOZYMES
,
TURNOVER NUMBER
.
Enzyme Denaturation The loss of enzyme
(catalytic) activity due to loss of the correct
functional structure of the protein. Denatur-
ation may be caused by factors such as expo-
s u r e   t o   h e a t   a n d   o rga n i c   s o l ve n t s ,
degradation of the enzyme molecule by pro-
teases, oxygen, and acid or alkaline pH. See
also
ENZYME
,
CONFORMATION
,
DENATURATION
,
EXTREMOZYMES
.
Enzyme Derepression Commonly known as
induction (of an enzyme). Initially a repres-
sor protein is bound to a specific region of
DNA. This binding inhibits transcription to
mRNA, thus blocking the synthesis of the
protein (enzyme) specified by the mRNA.
When present, the inducer molecule binds to
the repressor protein and inactivates it. Thus
the inhibition caused by the repressor protein
is overcome and mRNA can be synthesized,
which consequently leads to synthesis of the
mRNA-specified protein (enzyme). The
word derepression is sometimes used
because the repressor protein is, by itself,
active in repressing protein (enzyme) syn-
thesis. Its repressive action is mitigated
(derepressed) by the inducer molecule.
Hence, derepression (or unrepression) of
repression equals induction. See also 
CON-
TINUOUS PERFUSION
,
ENZYME REPRESSION
,
ENZYME
,
REPRESSION
 (
OF AN ENZYME
).
Enzyme Immunoassay (EIA) See
ELISA
.
Enzyme Repression Inhibition of enzyme
synthesis caused by the availability of the
product of that enzyme. On a molecular level
a repressor molecule (which could be, e.g.,
the amino acid arginine) combines with a spe-
cific repressor protein that is present in the
cell. This repressor molecule/repressor pro-
tein complex is then able to bind to a specific
region of DNA at the initial end of the gene
which is called the operator region. It is in
this region where the synthesis of mRNA is
initiated. The repressor “roadblock”  thus
© 2002 by CRC Press LLC

E
stops the synthesis of mRNA, and therefore
the synthesis of the protein is also blocked.
See also 
ENZYME
,
REPRESSION
 (
OF AN ENZYME
),
ENZYME DEPRESSION
.
Enzyme-Linked Immunosorbent Assay See
ELISA
.
Eosinophils Polymorphonuclear leukocytes
made in the bone marrow. They circulate in
the blood for a number of hours (three to
eight) and then migrate into the tissue where
they reside. They kill parasites too large to
be phagocytized by secreting substances that
kill the parasites (hookworms, trichinosis,
etc.), inhibit histamine release from mast
cells, and secrete chemicals that neutralize
histamine. Allergy causes an increase in
eosinophils. GM-CSF stimulates eosinophil
production. See also 
POLYMORPHONUCLEAR
LEUKOCYTES
  (
PMN
),
BASOPHILS
,
ANTIGEN
,
CELLULAR IMMUNE RESPONSE
.
EPD See
EXPECTED PROGENY DIFFERENCES
.
Epidermal Growth Factor (EGF) A protein
of 53 amino acids that greatly increases
growth/reproduction of epidermal (skin)
cells. This protein also increases growth of
wool in sheep and growth in more than 50%
of human tumors. High concentrations of
epidermal growth factor are found in human
tears. EGF was discovered by Stanley
Cohen. See also 
PROTEIN
,
EGF RECEPTOR
,
GROWTH FACTOR
,
NERVE GROWTH FACTOR
 (
NGF
),
AMINO ACID
,
FILLER EPITHELIAL CELLS
,
TUMOR
.
Epidermal Growth Factor Receptor See
EGF
RECEPTOR
,
HER
-2
RECEPTOR
,
HER
-2
GENE
.
Epimerase An enzyme capable of the revers-
ible interconversion of two epimers. See also
ENZYME
,
EPIMERS
.
Epimers Two stereoisomers differing in con-
figuration. See also 
CONFIGURATION
,
STEREOI-
SOMERS
.
Episome (of a bacterium) An independent
genetic element (DNA) that occurs inside
bacterium in addition to the normal bacterial
cell genome. The episome can replicate either
as an autonomous unit or as one integrated
into the host genome. The F (fertility) factor
is an episome. See also 
GENOME
,
PLASMID
,
BACTERIA
,
DEOXYRIBONUCLEIC ACID
 (
DNA
).
Epistasis Interaction between nonallelic genes
in which the presence of a certain allele at
one locus prevents expression of an allele at
a different locus. See also 
ALLELE
,
GENE
,
EXPRESS
,
LOCUS
.
Epithelial Projections Projections that anchor
the epidermis (surface skin) to the dermis
(subsurface tissue). Growth of these projec-
tions is increased by epidermal growth factor
during the wound healing process. See also
EPIDERMAL GROWTH FACTOR
 (
EGF
).
Epithelium The prefix epi- means on, above,
or upon. The membranous cellular tissue that
covers a free surface or lines a tube or cavity
of an animal body. It serves to enclose and
protect the other tissues, to produce secretions
and excretions, and to function in assimila-
tion. See also 
ASSIMILATION
,
CADHERINS
,
ION
CHANNELS
.
Epitope Also called antigenic determinant. The
specific group of atoms (on an antigen mole-
cule) that is recognized by (that antigen’s)
antibodies (thereby causing an immune
response). See also 
ANTIBODY
,
ANTIGEN
,
IDIO-
TYPE
,
HUMORAL IMMUNE RESPONSE
.
EPO See
ERYTHROPOIETIN
,
EUROPEAN PATENT
OFFICE
.
EPPO See
EUROPEAN PLANT PROTECTION ORGANI-
ZATION
.
EPSP Synthase Enolpyruvyl-shikimate phos-
phate synthase. An enzyme produced by vir-
tually all plants and internally transported
into their cells’ chloroplasts, it is essential
in a plant’s metabolism biochemical path-
way and for the biosynthesis (creation) of
the aromatic (ring-shaped molecule) amino
acids tyrosine, phenylalanine, and tryp-
tophan, which are needed for plants to live.
Some (glyphosate-containing and sulfosate-
containing) herbicides kill unwanted plants
(e.g., weeds) by inhibiting EPSP synthase.
By incorporating a gene that causes (over-)
production of CP4 EPSP synthase into sev-
eral crops (soybeans, cotton, etc.), scientists
have been able to help those crops survive
post-emergence application(s) of glypho-
sate-containing herbicide. Additional resis-
tance to glyphosate-containing and
sulfosate-containing herbicides can be con-
ferred to plants by incorporating into plants
a gene (GO) which causes those plants to
produce glyphosate oxidase. See also
ENZYME
,
METABOLISM
,
GENE
,
PAT GENE
,
BAR
GENE
,
GENETIC ENGINEERING
,
SOYBEAN PLANT
,
© 2002 by CRC Press LLC

E
CORN
,
GLYPHOSATE
,
GLYPHOSATE OXIDASE
,
CP
4
EPSPS
,
HERBICIDE
-
TOLERANT CROP
,
SULFOSATE
,
m
EPSPS
,
CHLOROPLASTS
,
CHLOROPLAST TRANSIT
PEPTIDE
  (
CTP
),
TARGET
  (
OF A HERBICIDE OR
INSECTICIDE
).