E

E-Selectin See ELAM-1.

EAA See ESSENTIAL AMINO ACIDS.

EAA See EXCITATORY AMINO ACIDS (EAAs).

Early Development The period of a phage infection before the start of DNA replication.

See also PHAGE, BACTERIOPHAGE, DEOXYRIBO-

NUCLEIC ACID (DNA).

Early vs. Late Genes T h o s e g e n e s t r a n - scribed early in a bacteriophage-mediated infection process as compared to those genes transcribed some time later. May require different “p factors” (sigma) for recognition of promotors. See also GENE, PROMOTER.

Early vs. Late Proteins During viral infection, viral-specific proteins are synthesized at characteristic times after infection. They are called “early” and “late.” Often under positive control of bacterial and viral sigma fac-

tors. See also EARLY VS. LATE GENES, PROTEIN.

Earthworms (Eisenia foetida) These worms live in the soil and consume up to ten tons of organic matter (old crop plant stalks, husks, etc.) per acre (approximately 0.4 hectare) per year. In so doing, earthworms make the soil more fertile, since the process breaks down that organic matter into soil (when excreted by those earthworms). Earthworm tunnels also help aerate soil, which encourages healthy plant root systems. See also

LOW-TILLAGE CROP PRODUCTION, GLOMALIN, NO-

TILLAGE CROP PRODUCTION.

E. coli See ESCHERICHIA COLIFORM (E. COLI).

E. coli 0157:H7 See ESCHE RICHIA COL IFORM

0157:H7 (E. COLI 0157:H7).

ECB See EUROPEAN CORN BORER (ECB).

Ecology The study of the interrelationships between organisms and their environments. See also HABITAT.

Ectodermal Adult Stem Cells Certain stem cells present within (adult) bodies of organisms, that can be differentiated (via chemical

0-8493-XXXX-X/01/$0.00+$1.50 © 2001 by CRC Press LLC

	signals) to give rise to cells of skin, hair,
		E
	tooth enamel, mucous membranes, and some
	glandular tissues. See also STEM CELLS, MUL-
	TIPOTENT ADULT STEM CELLS, CELL, ORGANISM,
	SIGNALING.
	Edible Vaccines Edible substances, bearing
	antigens, that cause activation of an animal’s
	immune system via that animal’s GALT
	(gut-associated lymphoid tissues). These
	“edible vaccines” are derived from transgenic
	plants (grains, tubers, fruits, etc.) or eggs
	(i.e., via the activation of the hen’s immune
	system to cause that hen to secrete desired
	molecule(s) into the eggs it lays). See also
	GUT-ASSOCIATED LYMPHOID TISSUES (GALT), ANTI-
	GEN, CELLULAR IMMUNE RESPONSE, MOLECULAR
	PHARMING™, HUMORAL IMMUNITY, PLANTIGENS.
	EDTA Ethylenediamine tetraacetate. An organic
	molecule which, due to the chemical groups
	it contains and their juxtaposition within that
	molecule, is able to chelate (bind) certain
	other molecules such as divalent metal cations.
	EDTA thus inhibits some enzymes requiring
	such ions for activity. See also CHELATION,
	COFACTOR, CHELATING AGENT.
	EFA See ESSENTIAL FATTY ACIDS.
	Effector A class of (usually small) molecules
	that regulates the activity of a specific protein
	(e.g., enzyme) molecule by binding to a spe-
	cific site on the protein. Control of (existing)
	enzyme molecules may be achieved by com-
	bination of the effector with the enzyme. The
	effector molecule may either physically
	block the active site on the enzyme mole-
	cule, or alter the three-dimensional confor-
	mation of the enzyme molecule. That
	conformation change results in a change in
	the enzyme’s catalytic activity. Effector is a
	general term. Effector molecules may be
	activators (cause an increase in the enzyme’s
	catalytic activity) or inhibitors (cause a

© 2002 by CRC Press LLC

decrease in the enzyme’s catalytic activity). A special class of effector, known as an allosteric effector, binds to the enzyme molecule at a site other than the enzyme’s active site (thereby activating or inhibiting). See

also PROTEIN, ENZYME, CONFORMATION, ALLOS-

TERIC ENZYMES, ALLOSTERIC SITE, ACTIVE SITE,

FEEDBACK INHIBITION, CATALYTIC SITE.

EEGF Receptor A protein embedded in theSee EPIDERMAL GROWTH FACTOR (EGF).EGF

surface of the membranes of skin cells. The receptor consists of (1) an outside (of the cell membrane) enzyme that recognizes epidermal growth factor (EGF) and binds to it, and (2) an enzyme on the inside of the cell membrane, which is of the tyrosine kinase class. When free EGF comes in contact with an EGF receptor, they bind (in a lock-and- key fashion) and then enter the cell together (through the cell membrane. There EGF stimulates growth or division of the cell via ras protein and ras gene). The EGF receptor (and receptors in general) is like a butler who allows the EGF (a guest) to enter the cell

(home). See also ONCOGENES, PROTEIN, PLASMA MEMBRANE, TRANSMEMBRANE PROTEINS, ras GENE,

ras PROTEIN, RECEPTORS, SIGNAL TRANSDUCTION.

EGFR See EGF RECEPTOR.

EHEC See ENTEROHEMORRHAGIC E. COLI.

EIA See ENZYME IMMUNOASSAY (EIA).

Eicosanoids A group of chemical compounds which the human body synthesizes (manufactures) from arachidonic acid, docosahexanoic acid, and other starting materials. One subgroup of eicosanoids is that of the prostaglandins (cyclic fatty acids that act as hormones in the body). For example, the COX-1 enzyme converts arachidonic acid to constitutive prostaglandins, and the COX-2 enzyme converts arachidonic acid to inducible prostaglandins. See also ARACHIDONIC

ACID (AA), CYCLOOXYGENASE, CONSTITUTIVE

ENZYMES, INDUCIBLE ENZYMES, PROSTAGLAN-

DINS, HORMONE, COX-1, COX-2, LEUKOTRIENES.

Eicosapentaenoic Acid (EPA) See EICOSAPEN-

TANOIC ACID (EPA).

Eicosapentanoic Acid (EPA) O n e o f t h e omega-3 (n-3) polyunsaturated fatty acids (PUFA), EPA is important for the development of the human brain, retina tissue, prevention of high blood pressure, coronary

heart disease (CHD), and some cancers. The human body converts linolenic acid (e.g., from consumption of soybean oil) to the two highly unsaturated fatty acids (HUFA) eicosapentanoic acid (EPA) and docosahexanoic acid (DHA). See also N- 3 FATTY ACIDS, POLY-

UNSATURATED FATTY ACIDS (PUFA), UNSATUR-

ATED FATTY ACIDS, ESSENTIAL FATTY ACIDS,

CORONARY HEART DISEASE (CHD), CANCER,

HIGHLY UNSATURATED FATTY ACIDS (HUFA),

LINOLENIC ACID, SOYBEAN OIL.

ELAM-1 Also known as E-selectin, it is a selectin molecule that is synthesized by endothelial cells after (adjacent) tissue is infected. ELAM-1 molecules then help leukocytes leave the bloodstream to fight the

infection. See also SELECTINS, LECTINS, ADHESION MOLECULES, LEUKOCYTES.

Elastase An enzyme secreted by neutrophils (white blood cells that engulf pathogens) which catalyzes the cleavage (breakdown) of specific proteins that function to provide elasticity to certain tissues. May be indirectly responsible for some autoimmune diseases, such as arthritis (which results from breakdown of cartilage tissue). Elastase may also be indirectly responsible for the emphysema (caused by loss of lung elasticity) that results from prolonged smoke inhalation. When a-1 antitrypsin (anti-elastase) efficacy is reduced (via smoke), the now-unrestrained excess elastase destroys alveolar walls in the lungs by digesting elastic fibers and other connective tissue proteins. See also LEUKO-

CYTES, NEUTROPHILS, PROTEOLYTIC ENZYMES.

Electrolyte Any compound (salt, acid, base, etc.) which in aqueous solution dissociates into ions (charged atom-sized particles). Electrolytes may either be strong (completely or nearly completely dissociated) or weak (only partially dissociated). See also

ION.

Electron Carrier A protein, such as flavoprotein or a cytochrome, that can gain and lose electrons reversibly and function in the transfer of electrons from one carrier to another until the electron is taken up by a final molecule or atom such as oxygen. See

also PROTEIN, CYTOCHROME.

Electron Microscopy (EM) A technique for greatly magnifying and visualizing very

© 2002 by CRC Press LLC

PROTEIN,

small entities such as viruses and even large molecules. The technique uses beams of electrons instead of light rays. Because of the physics involved, beams of electrons permit much greater magnification than is possible with a light microscope. Electron microscopes have been used to examine the structures of viruses, bacteria, pollen grains, molecules, etc.

Electropermeabilization See ELECTROPORATION.

Electrophoresis A technique for separating molecules based on the differential movement of charged particles through a matrix when subjected to an electric field. The term is usually applied to large ions of colloidal particles dispersed in water. The most important use of electrophoresis (currently) is in the analysis of proteins, and then a technique known as gel electrophoresis is used. Since the proportion of proteins varies widely in different diseases, electrophoresis can be used for diagnostic purposes. Electrophoresis, through agarose or other gel matrices, is a common way to separate, identify, and purify plasmid DNA, DNA fragments resulting from digestion (of DNA) with restriction endonucleases, and RNA. Electrophoresis is also used to study bacteria and viruses, nucleic acids, and some types of molecules, including amino acids. See also

AMINO ACID, BIOLUMINESCENCE, POLYACRYLAMIDE

GEL ELECTROPHORESIS (PAGE), TWO-DIMENSIONAL

(2D) GEL ELECTROPHORESIS, CHROMATOGRAPHY,

GEL, AGAROSE, PLASMID, DEOXYRIBONUCLEIC

ACID (DNA), RESTRICTION ENDONUCLEASES, RIBO-

NUCLEIC ACID (RNA), BACTERIA, VIRUS, BIOMEMS.

Electroporation A process utilized to introduce a foreign gene into the genome of an organism. In 1995, the U.S. company Dekalb Genetics Corp. received a patent for producing genetically engineered corn via introduction of a foreign gene into corn cells via electroporation. Electroporation, also called electroporesis or electropermeabilization, uses a brief direct-current (dc) electrical pulse to cause formation of “micropores” (tiny holes) in the surface of cells or protoplasts suspended in a solution (water) containing DNA sequences (genes). After the gene(s) enter the cell via the temporarily created micropores, the electrical pulse

ceases, and the micropores close so that the gene(s) cannot depart the cell. The cell then incorporates (some) of the new genetic material (genes) into its genetic complement (genome), and creates whatever product (i.e., a protein) the newly-introduced gene

codes for. See also CODING SEQUENCE, GENETIC

ENGINEERING, VECTOR, BIOLISTIC® GENE GUN,
“EXPLOSION” METHOD, AGROBACTERIUM TUMEFA-		E
CIENS, GENE, GENOME, CELL, CORN, PROTOPLAST,
DEOXYRIBONUCLEIC ACID (DNA), PROTEIN.
Electroporesis See ELECTROPORATION.
ELISA (test for proteins) An enzyme-linked
immunosorbent assay (hence the acronym)
which can readily measure less than a nan-
ogram (10–9 g) of a protein. This assay is
more sensitive than simple immunoassay
(tests) because one of the two antibodies
used to bind and quantitate (measure) the
protein’s antigen, based on two concurrent
epitopes within the protein, is attached to an
enzyme. The enzyme can rapidly convert an
added colorless substrate into a colored
product or a nonfluorescent substrate into an
intensely fluorescent product (thus enabling
finer quantitation). See also ABSORBANCE (A),
IMMUNOASSAY, PROTEIN, ANTIGEN, ENZYME,
NANOGRAM (ng), FLUORESCENCE.
Elite Germplasm Refers to germplasm that is
adapted (selectively bred) and optimized to
new surroundings (i.e., environment). For
example, corn/maize (Zea mays L.), which
is native to Mexico, has been adapted and
optimized to grow in field conditions in
many of the world’s countries. See also
GERMPLASM, INTROGRESSION, MARKER ASSISTED
SELECTION,	CORN.
Ellagic Acid	A naturally occurring plant phe-
nol (phytochemical) that, when consumed
by humans, has been shown to help inhibit
some cancers. Ellagic acid is naturally
present in	strawberries, the pomegranate

( P u n i c a g r a n a t u m ) , e t c . S e e a l s o

PHYTOCHEMICALS, POLYPHENOLS, CANCER.

EMAS Eco-Management and Audit Scheme. Embryo Rescue Refers to the tissue culture

techniques/technologies utilized to enable the fertilized embryo resulting from a “wide cross” (between two nonsexually compatible plant species) to grow and mature into a seed

© 2002 by CRC Press LLC

producing plant. See also TRADITIONAL BREED-

ING METHODS, WIDE CROSS, TISSUE CULTURE.

		Embryology The study of the early stages in
		the development of an organism. In these
		stages a single highly specialized cell, the
		egg, is transformed into a complex many-
		celled organism resembling its parents. See
		also CELL, ANTIANGIOGENESIS, GAMETE.
		Embryonic Stem Cells See HUMAN EMBRYONIC
	E
		STEM CELLS.
		EMEA See EUROPEAN MEDICINES EVALUATION
		AGENCY (EMEA).
		Emulsion A stable dispersion of one liquid in a
		second, immiscible (i.e., nonmixable) liquid.
		For example, milk is an emulsion of oil (fat)
		in water, and latex paint is an emulsion of
		paint resin in water. Certain ingredients (e.g.,
		β-conglycinin protein) help enable a greater
		content of the first liquid to be dispersed in
		the second liquid. Certain ingredients (e.g.,
		β-conglycinin protein) make a given emul-
		sion more stable (i.e., prevent the two liquids
		from separating over an extended period of
		time). See also PROTEIN, β-CONGLYCININ.
		Enantiomers From the Greek word enantios,
		which means opposite. Enantiomers are a
		pair of nonidentical, mirror-image mole-
		cules. This means that both molecules are
		made up of the same atoms, i.e., they have
		the same molecular formula, but the constit-
		uent groups that are attached to a carbon
		atom can be arranged in two different ways
		(forms) around the carbon atom. This gives
		rise to an asymmetric molecule that can exist
		in either of two mirror-image forms whose
		mirror images are not superimposable. A pair
		of these molecules is known as enantiomers.
		The four attached groups are all different
		from each other. See also RACEMATE, OPTICAL
		ACTIVITY, CHIRAL COMPOUND, ENANTIOPURE.
		Enantiopure Refers to a compound (e.g., a
		pharmaceutical) that consists of only one of
		that compound’s two possible enantiomers.
		Sometimes expressed in relative terms. For
		example, 98% enantiopure would refer to a
		compound that consists of 98% (of) desired
		enantiomer. See also ENANTIOMERS, CHIRAL
		COMPOUND, RACEMATE, OPTICAL ACTIVITY.
		Endergonic Reaction A chemical reaction with
		a positive standard free energy change (i.e., an
		“uphill” reaction). An (heat) energy-requiring

reaction. A nonspontaneous reaction at ambient temperature. See also EXERGONIC

REACTION, FREE ENERGY.

Endocrine Glands Glands that secrete their products (hormones) into the blood, which then carries them to their specific target organs. For example, adrenalin, produced in the adrenal glands, is carried to the heart (and other muscles) when needed during periods of stress. The endocrine glands are: the pituitary, thyroid, adrenals, pancreas, ovaries (in females), and testes (in males). Endocrine glands are found in some invertebrates as well as in vertebrates. See also

HORMONE, ENDOCRINE HORMONES.

Endocrine Hormones The products secreted by the endocrine glands. These help control long-term bodily processes, such as growth, lactation, sex cycles, and metabolic adjustment. The endocrine system and the nervous system are interdependent and often referred to collectively as the neuroendocrine system. For example, the juvenile hormone, found in insects and annelids, affects sexual maturation. There is currently great interest among scientists in the potential use of such hormones in the control of destructive insects. See

also ENDOCRINE GLANDS, HORMONE, PHEROMONES.

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 taking 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