Central Glossary

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Glossary

Acute-phase proteins

Proteins found in the blood shortly after the onset of an infection that participate in the early phases of the host defense against the infection.

Adaptive immunity

Response of antigen-specific immune cells when they encounter the antigen, including the development of immunological memory; also known as acquired immunity; adaptive immune responses are distinct from innate immune responses.

Affect

Emotion or subjectively experienced feeling.

Acetaldehyde

A toxic product that results from the breakdown of alcohol by the enzyme alcohol dehydrogenase (ADH).

Adenosine triphosphate (ATP)

A molecule, generated largely in the mitochondria, that provides the energy needed for many key metabolic functions.

Alcohol dehydrogenase (ADH)

An enzyme that breaks down alcohol by oxidation, converting it to acetaldehyde.

Allele

One of two or more variants of a gene or other deoxyribonucleic acid (DNA) sequence. Different alleles of a gene generally serve the same function (e.g., code for a protein that affects eye color) but may produce different phenotypes (e.g., blue eyes or brown eyes). Some alleles may produce a product that has no function or an abnormal function.

Anisotropy

Having a different value when measured in different directions. Anisotropy is the property of being directionally dependent, as opposed to isotropy, which implies homogeneity in all directions.

Anterior

Towards the front of an organism; opposite of posterior.

Antibodies

Immune molecules naturally produced by the body that recognize foreign or harmful molecules which have entered the body, bind to these molecules, and mark them for destruction by the body’s immune system.

Apoptosis

Cell death in which the affected cell participates by activating a cascade of biochemical reactions that leads to death.

Atrophy

The complete or partial wasting away of parts of the body; a physiological process of tissue breakdown involving cell death.

Antigen

Any molecule that can bind specifically to an antibody and generate an immune response.

Antioxidant

A substance (e.g., glutathione and vitamins A and E) that inhibits oxidation, serving as a defense against harmful reactive oxygen species (ROS).

Arrhythmia

Any condition in which there is abnormal electrical activity in the heart (i.e., the heart beat is too fast, too slow, or irregular).

Atherosclerosis

Condition in which the walls of the arteries thicken because of the buildup of fatty materials, such as cholesterol; may lead to complete blockage of the artery.

Atherosclerotic plaque

The buildup of cells, lipids (e.g., cholesterol), calcium, and connective tissue that forms in the artery walls during atherosclerosis.

Cardiomyopathy

Condition characterized by the deterioration of the function of the heart muscle (i.e., myocardium).

CD4

Protein present on the surface of certain T-cells (helper T-cells) that helps the T-cell recognize and bind to their specific antigens; also serves as co-receptor for the human immunodeficiency virus.

CD8

Protein present on the surface of certain T-cells (cytotoxic T-cells); also involved in the recognition of specific antigens by the T-cells.

Cell-mediated response

Any immune response mediated by the actions of immune cells rather than molecules secreted by these cells; sometimes more specifically used to refer to any adaptive immune response in which antigen-specific T-cells have the main role.

Cerebellum

A region at the lower back of the brain that controls sensory perception and coordination of movement and contributes to certain higher-order cognitive and affective functions.

Cerebrospinal fluid (CSF)

Fluid that surrounds the brain and spinal cord and fills the ventricles and cortical sulci.

Chemokines

Small signaling proteins that stimulate the migration and activation of cells (e.g., macrophages); have a central role in inflammatory responses.

Cholesterol

A fat-soluble substance widely distributed in the body (e.g., in blood, brain tissue, liver, and nerve fibers) that is continuously produced in the body and taken up with foods of animal origin; can be classified into “good” cholesterol (i.e., high-density lipoprotein [HDL]) and “bad” cholesterol (i.e., low-density lipoprotein [LDL]), which is associated with an increased risk of heart disease.

Chromatin

The combination of deoxyribonucleic acid (DNA) and proteins that makes up chromosomes.

Ciliated (cells)

Cells with hair-like protrusions (e.g., in the airways) that serve to propel foreign particles (e.g., dust, bacterial fragments) out of the body.

Collagen

The major protein of fibrous connective tissue involved in the production of scar tissue; produced in the liver by stellate cells.

Complement

Set of plasma proteins that act together to attack extracellular pathogens; the proteins cover the pathogen, which facilitates pathogen removal by phagocytes.

Complementary DNA (cDNA)

A segment of DNA identical in sequence to at least part of the coding sequence of a gene, generated in the laboratory from a natural messenger RNA (mRNA) molecule. cDNA can be produced in large quantities for sequencing and other genetic studies.

Complicated alcoholism

Alcoholism exacerbated (or complicated) by the presence of other co-occurring conditions, such as Korsakoff’s syndrome (KS).

Computed tomography (CT)

Imaging method using computer processing to generate a three-dimensional image from a large series of two-dimensional X-ray images taken around a single axis of rotation; allows identification of characteristics of the internal structure of an object.

Concordance

The presence of the same trait in both members of a pair of twins (or a set of individuals).

Confidence interval (CI)

A statistical measure that can be used to determine how reliable the value of a measurement is. The 95 percent CI gives an estimated range for the measurement that has a 95 percent likelihood it includes the actual value. The larger that range, the less reliable is the measurement.

Coronary artery disease

End result of the accumulation of atherosclerotic plaques in the walls of the arteries that supply the heart muscle with blood; often used synonymously with coronary heart disease, although coronary heart disease also can have causes other than coronary artery disease.

Coronary heart disease

Any abnormal condition that affects the blood vessels supplying the heart muscle, thereby resulting in reduced flow of oxygen and nutrients to the heart muscle and impairing the heart’s ability to pump blood into the body.

Corpus callosum

The largest connective pathway in the human brain. It is made of nerve fibers that connect the left and right sides (hemispheres) of the brain.

Cytochromes

Specialized enzymes within mitochondria and other cell structures. Different cytochromes play important roles in metabolizing toxic substances, drugs, and other chemicals, as well as in producing adenosine triphosphate (ATP).

Cytokines

A family of molecules, produced primarily by cells of the immune system, that regulate cellular interactions and other functions. Many cytokines play important roles in initiating and regulating inflammation.

Cytosol

Fluid contained within the cell, where several biochemical reactions (e.g., glycolysis) take place.

Demyelination

Loss of the myelin sheath of nerve cells.

Diffusion tensor imaging (DTI)

Magnetic resonance imaging (MRI) method to produce in vivo images of biological tissues by measuring local characteristics of the passive movement (i.e., diffusion) of water molecules; used for imaging of tissues that have an internal fibrous structure, such as the myelin sheath covering nerve fibers; in these cases, water molecules can more easily diffuse along the direction of the fibrous structure than perpendicular to it, a property called anisotropy.

Diffusivity

The rate of passive movement (i.e., diffusion) of a water molecule in a fluid or tissue.

Dorsal

Toward the backside of an organism; opposite of ventral.

Deoxyribonucleic acid (DNA)

A family of large molecules within the cells of an organism that carry genetic information by specifying the structure of proteins.

Endophenotype

A heritable trait or characteristic that is not the condition under investigation but has been shown to be associated with the condition; for example, certain neurobiological characteristics have been noted in people with alcoholism and may be used as endophenotypes to identify people at risk for alcoholism.

Endothelium

Layer of cells lining the body cavities and blood vessels.

Endotoxin

A highly toxic chemical component of the cell walls of bacteria that occur normally in the intestine. Endotoxin can be released into the bloodstream when the bacteria die.

Enzyme

A substance (usually a protein) that directs and accelerates chemical reactions in the body but does not itself undergo permanent change.

Epigenetic

Referring to heritable changes in phenotype or gene expression caused by mechanisms other than changes in the underlying deoxyribonucleic acid (DNA) sequence.

Ester

An organic chemical compound formed by the reaction of an organic acid (e.g., acetic acid) and an alcohol.

Event-related potential

A characteristic pattern of brain waves elicited when a person is exposed to a stimulus (e.g., a sudden sound or light).

γ-aminobutyric acid (GABA)

A neurotransmitter that in the brain acts to reduce the activity of the signal-receiving nerve cell (i.e., an inhibitory neurotransmitter); helps to restore stable conditions (i.e., homeostasis) in a stressful situation.

Fatty acids

Building blocks of fat molecules. Alcohol interferes with the normal metabolism of fatty acids and promotes the deposit of dietary fat in the liver.

Fibrosis

The formation of scar tissue.

Free radicals

Highly reactive molecular fragments that frequently contain oxygen. (See reactive oxygen species [ROS])

Genome-wide association study (GWAS)

An examination of genetic variation associated with observable traits across the genome, using single nucleotide polymorphisms (SNPs).

Gavage

Introduction of nutrients directly into the stomach via a feeding tube.

Genotype

The genetic makeup of an individual organism that is determined by the specific alleles of each gene carried by the individual.

Genu

The anterior end of the corpus callosum.

Glutathione (GSH)

An antioxidant molecule found naturally in the body, composed of three amino acids (i.e., glutamate, cysteine, and glycine).

Hepatitis

Generalized inflammation of the liver, often accompanied by tissue death and fibrosis. Alcoholic hepatitis can be fatal, but may be reversible with abstinence.

Hepatocytes

The principal cells of the liver, which carry out most of the liver’s metabolic activities.

Heterozygous

Carrying two different alleles of a given gene. Contrasts with homozygous, where both alleles are the same.

High-density lipoprotein (HDL)

A type of lipoprotein that transports cholesterol from the tissues to the liver for excretion or reuse; also known as “good” cholesterol.

Hippocampus

A seahorse-shaped gray-matter structure in the medial borders of the temporal lobes in each cerebral hemisphere; a principal function is in consolidation of new memories.

Humoral response

Immune response mediated by proteins in the blood; more specifically used to refer to the antibody-mediated arm of the adaptive immune response.

Inbred strain

Animal strain generated by repeatedly inbreeding brother–sister pairs so that ultimately all animals of the strain are genetically identical.

In vitro

Literally translated as “in glass;” refers to experiments conducted with isolated cells or tissues or with cells or tissues grown in culture dishes

In vivo

Refers to experiments conducted in an intact animal.

Infarct

An area of tissue death resulting from a local lack of oxygen that is caused by obstruction of blood supply.

Inferior

Located toward the feet of an organism; opposite of superior.

Inflammation

A defensive response to local tissue injury or infection, serving to prevent the spread of injury and activate the immune system; regulated by cytokines. Prolonged or excessive inflammation can damage healthy tissue, as in alcoholic liver disease.

Inhibitor

Molecule that binds to an enzyme or other protein and decreases its activity.

Innate immunity

Immune response whose components are present in the body from birth that is not specific to a particular antigen and does not increase in intensity with repeated exposure to a pathogen.

Interferons

A group of proteins that increase the resistance of cells to viral infection. Interferons also act as cytokines and can enhance some immune responses.

Interleukins

Cytokines of the immune system.

Ischemia

A condition in which blood flow is restricted to a part of the body.

Ischemia/reperfusion injury

Injury caused to tissue when blood supply to the tissue is first interrupted (see ischemia) and then re-established; is caused by oxidative stress caused by the absence of oxygen and nutrients during the ischemia.

Korsakoff’s syndrome (KS)

Brain disorder characterized primarily by the inability to form new memories; resulting from the thiamine (vitamin B1) deficiency of Wernicke’s encephalopathy (WE).

Kupffer cells

Specialized immune cells in the liver that filter bacteria and other foreign substances from the blood, and produce antibodies and cytokines.

Limbic system

A group of brain structures that together control such functions as emotional behavior and long-term memory.

Linkage analysis

The comparison of subjects within a family to evaluate the relationship/correlation between an allele and a phenotype (e.g., a disease).

Lipids

Fatty substances, including simple fats, their major components (i.e., fatty acids), and various fat-soluble substances (e.g., cholesterol).

Lipoprotein

A biochemical complex that contains both lipids (e.g., cholesterol) and proteins.

Low-density lipoprotein (LDL)

A type of lipoprotein that transports cholesterol from the liver to the tissues; high levels of LDL are associated with cardiovascular disease; therefore, it also is known as “bad” cholesterol.

Locus

A specific location on a chromosome.

Macrophage

A phagocyte residing in tissues throughout the body. In addition to ingesting foreign particles and microorganisms, macrophages synthesize proteins and other substances important in inflammatory responses, including cytokines. Macrophages that reside in the liver are called Kupffer cells.

Magnetic resonance imaging (MRI)

A medical imaging technique that uses a powerful magnetic field to align hydrogen atoms found in water in the body; when exposed to a radio frequency pulse, the hydrogen atoms create a magnetic field detectable by a scanner. This signal can be manipulated to visualize detailed internal structures of tissue.

Mammillary bodies

A pair of small round bodies on the undersurface of the brain connecting several neural pathways to and from various parts of the brain, possibly involved in memory functions.

Marker

A deoxyribonucleic acid (DNA) sequence whose chromosomal location has been determined and is known to have at least two forms (alleles), making it useful for identifying the locus of an associated gene.

Mental set

A cognitive strategy used while solving a problem.

Meta-analysis

An analysis that combines the results of several studies addressing a set of related research hypotheses.

messenger RNA (mRNA)

Key intermediary molecules that are generated when a gene is expressed (i.e., when the information encoded in the gene is converted into a protein product by the cell).

Methylation

The addition of a methyl group to another molecule; methylation of certain deoxyribonucleic acid (DNA) regions can alter the expression of the genes located in those regions; this is an example of an epigenetic mechanism of gene regulation.

Microarray technology

An automated, high-throughput technique for simultaneously analyzing thousands of different deoxyribonucleic acid (DNA) or RNA sequences.

microRNA (miRNA)

A tiny piece of RNA that binds to a matching piece of messenger RNA (mRNA) to make it double-stranded and decrease the production of the corresponding protein.

Microsatellite

Highly polymorphic loci found every few thousand nucleotides in the deoxyribonucleic acid (DNA) that can be used as markers to determine from which parent or ancestor a specific DNA sequence has been inherited. Microsatellites typically consist of short sequences of one to six nucleotides that can be repeated 10 to 100 times. Each person or animal has a specific pattern of microsatellites that can be used to determine inheritance patterns.

Microsomal ethanol-oxidizing system (MEOS)

An enzyme system that breaks down alcohol and generates toxic products such as acetaldehyde and oxygen radicals.

Microtubules

Minute tubules composed of the protein tubulin that are found in the fluid filling the cells and which form important structural components.

Mitochondria

Structures within cells that generate most of the cells’ energy through the production of adenosine triphosphate (ATP), which provides the energy needed for many key metabolic reactions.

Myelin

A white fatty material composed chiefly of alternating layers of lipids and lipoproteins that encloses the long nerve cell extension (i.e., axons) like a sheath to provide insulation

Myelinolysis

Dissolution or unfurling of the myelin sheaths of nerve fibers

Neurogenesis

The process by which new nerve cells (i.e., neurons) are generated.

Neurotransmitter

Signaling molecules produced in nerve cells (i.e., neurons) that serve to transmit signals from one neuron to another neuron or from a neuron to another type of cell (e.g., muscle cell); neurotransmitters are released from the signal-emitting neuron and bind to receptors on the surface of the signal-receiving cell.

Nucleotide

A building block of RNA or deoxyribonucleic acid (DNA) that consists of a base, a sugar, and a phosphate group.

Opportunistic infections

Infections by pathogens that cause disease only in people with a compromised immune system but not in people with a healthy immune system.

Opsonization

Alteration of the surface of a pathogen or other particle (e.g., by covering it with complement or antibodies) so that it can be ingested by phagocytes.

Oxidation

A chemical reaction that usually involves removing a hydrogen atom from a molecule or adding oxygen to it (or both).

Oxidative stress

An imbalance between oxidants (e.g., reactive oxygen species [ROS]) and antioxidants that can lead to excessive oxidation and cell damage.

Palpitation

A conscious (abnormal) awareness of the heartbeat.

Polyphenolic compound

A compound containing more than one phenol unit per molecule; a phenol is any compound that contains a six-carbon aromatic ring, linked directly to a hydroxyl group (OH).

Phenotype

An observable property, trait, or physical appearance of an organism resulting from the interaction of the genotype with environmental factors.

Phagocyte

A white blood cell capable of ingesting foreign particles and microorganisms.

Phagocytosis

Process by which phagocytes engulf pathogens or other particles, internalize them, and destroy them with enzymes stored in the phagocytes.

Plasma cells

B-cells in the final stage of differentiation that produce antibodies and secrete them into the blood.

Point mutation

A change in a single nucleotide of the genome. Also see single nucleotide polymorphism (SNP).

Polymorphism

The presence of two or more alleles of a gene or other deoxyribonucleic acid (DNA) sequence in a population.

Pons

A structure located on the brain stem that relays sensory information.

Posterior

Toward the back or rear (e.g., the posterior region of the brain is located toward the back of the head); opposite of anterior.

Proteins

Large molecules composed of long chains of amino acids linked together. Proteins help maintain the cell’s structure and participate in many biological functions, including the regulation of metabolic reactions. The shape and function of a protein is determined by the sequence of its amino acids.

Quantitative trait locus (QTL)

A deoxyribonucleic acid (DNA) region that is associated with a quantitative trait and which may contain one or more of the genes contributing to that trait.

Reactive oxygen species (ROS)

Highly reactive, oxygen–containing free radicals that are generated during oxidative metabolism. ROS can react with and damage lipids, proteins, and deoxyribonucleic acid (DNA) in cells, causing oxidative stress.

Receptor

Protein that binds to specific molecules (e.g., neuro-transmitters) to initiate intracellular activity.

Reperfusion

Restoration of blood flow through a tissue after a period of ischemia.

Selectively bred line

Lines of animals generated by breeding together those animals in a population that both have either very high, or very low levels of a phenotype of interest (e.g., voluntary alcohol consumption); after several generations of selective breeding, the resulting lines will exhibit stable differences in the phenotype of interest; the animals within a selectively bred line are not genetically identical.

Sepsis

Frequently fatal infection of the blood stream.

Single-nucleotide polymorphism (SNP)

A deoxyribonucleic acid (DNA) sequence variation that results from the exchange of only a single DNA building block (i.e., nucleotide), useful as markers.

Splenium

The posterior region of the corpus callosum.

Stellate cells

Star-shaped liver cells that serve as the primary storage site for vitamin A compounds and fat molecules; their activation plays a central role in the development of fibrosis.

Sulcus (pl. sulci)

Spaces between the foldings of brain tissue.

Superior

Toward the head (or top of the head) of an organism; opposite of inferior.

Superoxide

A destructive reactive oxygen species (ROS) produced as a byproduct of some oxidation reactions.

Synaptic transmission

Transmission of nerve signals from one nerve cell to another or from a nerve cell to another type of cell that occurs at a synapse—the junction between the nerve ending of the signal-emitting cells and a receptor-carrying region of the signal-receiving cell; involves the release of chemical messengers (neurotransmitters) from the signal-emitting cell that interact with receptors on the signal-receiving cell.

Thalamus

A large, dual-lobed mass of gray-matter cells located at the top of the brainstem. It receives auditory, somatosensory, and visual sensory signals and relays sensory signals to the cerebral cortex.

Tumor necrosis factor alpha (TNF-α)

A type of cytokine that promotes inflammatory responses, stimulates neutrophils and macrophages, induces fever, and induces macrophages to produce cytokines.

Uncomplicated alcoholism

Alcoholism without the presence of co-occurring medical conditions.

Ventral

Toward the belly-side of an organism.

Ventricle

Fluid-filled space in the brain.

Vermis

A complex brain structure (vermis means “wormlike”) composed of 10 lobules residing between the cerebellar hemispheres.

Voltage-dependent ion channel

A pore or channel spanning the cell membrane whose opening and closing is controlled by electrical impulses; once opened, the channel allows passage of charged molecules (i.e., ions) into or out of the cell.

Voxel

A volume element, representing a value on a regular grid in three-dimensional space.

Wernicke’s encephalopathy (WE)

A severe syndrome resulting in damage to multiple brain areas and characterized by poor balance and gait (i.e., ataxia), disturbance of eye movements (i.e., ophthalmoplegia), mental confusion, and impairment of short-term memory. WE results from inadequate intake or absorption of thiamine (vitamin B1) coupled with continued carbohydrate ingestion and can lead to the development of Korsakoff’s syndrome (KS).

White matter

A generic term for a collection of nerve cell fibers (i.e., axons) in the central nervous system.