test

DEFINITION:

1. An examination or trial.

2. A significant chemical reaction.

3. A reagent.

4. A loose or rigid, secreted or agglutinated, protective shell or shell-like covering or exoskeleton, seen in various invertebrates, including certain protozoa and echinoderms.

hypothesis

DEFINITION:

A supposition that appears to explain a group of phenomena and is advanced as a basis for further investigation; a proposition that is subject to proof or to an experimental or statistical test.

G protein-coupled receptors

DEFINITION:

G protein-linked (or coupled) receptors mediate the cellular responses to an enormous diversity of signaling molecules, including hormones, neurotransmitters, and local mediators, which are as varied in structure as they are in function: the list includes proteins and small peptides, as well as amino acid and fatty acid derivatives.

Despite the chemical and functional diversity of the signaling molecules that bind to them, all of the G protein-linked receptors whose amino acid sequences are known from DNA sequencing studies have a similar structure and are almost certainly evolutionarily related. They consist of a single polypeptide chain that threads back and forth across the lipid bilayer seven times.

The members of this receptor family have conserved not only their amino acid sequence but also their functional relationship to G proteins by means of which they broadcast into the interior of the cell the message that an extracellular ligand is present.

multiple

DEFINITION:

1. More than one.

2. Occurring in or affecting various parts of the body at once.

3. The product of a quantity by an integer.

intracellular

DEFINITION:

Situated or occurring within a cell or cells.

extracellular loops

DEFINITION:

The turns or sharp curves in a cordlike structure appearing outside a cell's membrane, usually referring to a protein whose subunits are exposed on both sides of a cell membrane. For an example, click here.

bind

DEFINITION:

To form a weak, reversible chemical bond, e.g., antigen to antibody or hormone to receptor.

G proteins

DEFINITION:

Any of a family of similar heterotrimeric proteins of the intracellular portion of the plasma membrane that bind activated receptor complexes and, through conformational changes and cyclic binding and hydrolysis of GTP, directly or indirectly effect alterations in channel gating and so couple cell surface receptors to intracellular responses. Some G proteins are named for their activities, e.g., G_s stimulates and G_I inhibits enzyme activity.

immunocytochemical

DEFINITION:

Pertaining to the application of immunochemical techniques, e.g., immunoperoxidase staining, to cytochemistry.

ELISA

DEFINITION:

(Enzyme-Linked ImmunoSorbent Assay) any enzyme immunoassay utilizing an enzyme-labeled immunoreactant (antigen or antibody) and an immunosorbent (antigen or antibody bound to a solid support). A variety of methods (e.g., competitive binding between the labeled reactant and unlabeled unknown [e.g., a sandwich technique in which the unknown (an antigen) binds both the immunosorbent and labeled antibody]) may be used to measure the unknown concentration.

expression

DEFINITION:

1. The aspect or appearance of the face (or surface of a cell) as determined by the physical or emotional state.

2. The act of squeezing or evacuating by pressure; a term used in pharmacy, surgery, and obstetrics.

3. The detectable effect of a gene.

4. A representation of value, relation, or the like (e.g., ratio).

subcellular

DEFINITION:

Below the cellular level.

localization

DEFINITION:

1. The determination of the site or place of any process or lesion.
2. Restriction to a circumscribed or limited area.
3. Prelocalization.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

N

DEFINITION:

Symbol for newton , nitrogen , and for normal (solution), used with a number designating the strength of the solution relative to the normal, e.g., N/2 or 0.5 N for half-normal.

C-terminal

DEFINITION:

The end of the peptide chain carrying the free alpha carboxyl group of the last amino acid, conventionally written to the right.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

localized

DEFINITION:

Not general; restricted to a limited region or to one or more spots.

plasma membrane

DEFINITION:

The structure enveloping a cell, enclosing the cytoplasm, and forming a selective permeability barrier; it consists of lipids, proteins, and some carbohydrates, the lipids thought to form a bilayer in which integral proteins are embedded to varying degrees.

expressed

DEFINITION:

1. Showing a detectable effect of a gene.

2. Made known; shown.

3. Squeezed out; extracted by pressing.

coexpression

DEFINITION:

To appear with or together.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

bind

DEFINITION:

To form a weak, reversible chemical bond, e.g., antigen to antibody or hormone to receptor.

antagonists

DEFINITION:

1. Muscles whose actions are the direct opposite of that of other muscles.

affinity

DEFINITION:

1. A special attraction for a specific element, organ, or structure.

2. Chemical affinity.

3. In immunology, a thermodynamic expression of the strength of interaction between a single antigen-binding site and a single antigenic determinant (and thus of the stereochemical compatibility between them), most accurately applied to interactions among simple, uniform antigenic determinants such as haptens. Expressed as the association constant (K liters mole^-1), which, owing to the heterogeneity of affinities in a population of antibody molecules of a given specificity, actually represents an average value (mean intrinsic association constant).

polypeptide

DEFINITION:

A peptide which on hydrolysis yields more than two amino acids; called tripeptides, tetrapeptides, etc., according to the number of amino acids contained.

G protein-coupled receptors

DEFINITION:

G protein-linked (or coupled) receptors mediate the cellular responses to an enormous diversity of signaling molecules, including hormones, neurotransmitters, and local mediators, which are as varied in structure as they are in function: the list includes proteins and small peptides, as well as amino acid and fatty acid derivatives.

Despite the chemical and functional diversity of the signaling molecules that bind to them, all of the G protein-linked receptors whose amino acid sequences are known from DNA sequencing studies have a similar structure and are almost certainly evolutionarily related. They consist of a single polypeptide chain that threads back and forth across the lipid bilayer seven times.

The members of this receptor family have conserved not only their amino acid sequence but also their functional relationship to G proteins by means of which they broadcast into the interior of the cell the message that an extracellular ligand is present.

receptor

DEFINITION:

1. A molecular structure within a cell or on the surface characterized by (1) selective binding of a specific substance and (2) a specific physiologic effect that accompanies the binding, e.g., membrane receptors for peptide hormones, neurotransmitters, antigens, complement fragments, and immunoglobulins and nuclear receptors for steroid hormones.

2. A sensory nerve terminal that responds to stimuli of various kinds; classified in various ways including by the type of stimulus and by the location in the body.

V2 receptor - The structure to which the antidiuretic hormone, arginine vasopressin binds.

permission

DEFINITION:

Formal consent; authorization.

chemistry

DEFINITION:

The science that treats of the elements and atomic relations of matter, and of the various compounds of the elements.