aquaporins

DEFINITION:

A family of membrane channel proteins that serve as selective pores through which water crosses the plasma membranes of many human tissues and cell types.

membrane

DEFINITION:

A thin layer of tissue which covers a surface, lines a cavity, or divides a space or organ.

apical membrane - Pertaining to or located at the apex.

basolateral membrane - Pertaining to the base and sides.

plasma membrane - 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.

postsynaptic membrane - The area of plasma membrane of a postsynaptic cell, either a muscle fiber or a neuron, that is within the synapse and has areas especially adapted for receiving neurotransmitters.

presynaptic membrane - Area of the plasma membrane of a presynaptic axon that is within the synapse and has sites (active zones) especially adapted for the release of neurotransmitters.

semipermeable membrane - A membrane that permits the passage of a solvent, such as water, but prevents the passage of the dissolved substance, or solute.

osmoregulation

DEFINITION:

The state of regulation of osmotic pressure especially in the body of a living organism.

bacteria

DEFINITION:

Plural of bacterium.

aquaporin-2

DEFINITION:

Also called WCH-CD, this water channel makes the principal cells of the inner medullary collecting duct in the kidneys more permeable to water. Lack of functional aquaporin-2 gene leads to a rare form of nephrogenic diabetes insipidus.

AQP2

DEFINITION:

Aquaporin-2.

collecting duct cells

DEFINITION:

The cells of the renal collecting tubule: the arcuate renal tubule, straight collecting tubule, and papillary duct considered together.

kidney

DEFINITION:

One of a pair of vertebrate organs situated in the body cavity near the spinal column that excrete waste products of metabolism, in man are bean-shaped organs about 4-1/2 inches long lying behind the peritoneum in a mass of fatty tissue, and consist chiefly of nephrons by which urine is secreted, collected, and discharged into a main cavity whence it is conveyed by the ureter to the bladder.

regulated

DEFINITION:

1. Having been adjusted to a certain standard.

2. In biology, describing the adaptation of form or behavior of an organism to changed conditions.

antidiuretic hormone

DEFINITION:

See vasopressin.

vasopressin

DEFINITION:

1. One of two octapeptide hormones formed by the neuronal cells of the hypothalamic nuclei and stored in the posterior lobe of the pituitary gland (neurohypophysis), the other being oxytocin. It stimulates the contraction of the muscular tissue of the capillaries and arterioles, raising the blood pressure. It promotes contraction of the intestinal musculature and increases peristalsis, and also exerts some contractile influence on the uterus. It also has a specific effect on the epithelial cells of the distal portion of the uriniferous tubule, augmenting resorption of water independently of solutes, resulting in concentration of urine and dilution of blood serum. Its rate of secretion is regulated chiefly by the osmolarity of the plasma.

2. [USP], A pharmaceutical preparation of the same principle, prepared synthetically or obtained from the posterior pituitary of healthy domestic animals used for food by man; used mainly as an antidiuretic in the treatment of acute or chronic diabetes insipidus, administered intramuscularly as a test of hypothalamo-neurohypophysial-renal function in distinguishing central from nephrogenic diabetes insipidus; it may also be used to stimulate smooth muscle tissue, especially to induce vasoconstriction in the presence of hemorrhage. Called also antidiuretic hormone (ADH).

two-dimensional

DEFINITION:

Having the dimensions of height and width only.

atomic

DEFINITION:

Of or pertaining to an atom.

microscopy

DEFINITION:

Examination under or observation by means of the microscope.

AQP2

DEFINITION:

Aquaporin-2.

aquaporin-1

DEFINITION:

Also known as CHIP-28, aquaporin-1 is the major water channel of the red blood cells. In the kidneys, it is involved in the reabsorption of most of the waste filtered through the glomerula.

AQP1

DEFINITION:

Aquaporin-1.

mapped

DEFINITION:

1. Having created on a flat surface a representation of an area, showing the relative position of various features.

2. Having located the relative position of genes on chromosomes.

C-terminus

DEFINITION:

The intracellular carboxy-terminus or tail of the vasopressin-2 receptor (V2R). See diagram.

AQP1

DEFINITION:

Aquaporin-1.

bovine

DEFINITION:

Pertaining to, characteristic of, or derived from cattle.

AQP1

DEFINITION:

Aquaporin-1.

putative

DEFINITION:

1. Commonly accepted or supposed.

2. Assumed to exist or to have existed.

cyclic guanosine monophosphate

DEFINITION:

A cyclic nucleotide, guanosine 3',5'-cyclic monophosphate, an intracellular "second messenger" similar in action to cyclic adenosine monophosphate; the two cyclic nucleotides activate different protein kinases and usually produce opposite effects on cell function. Abbreviated 3',5'-GMP, cGMP, and cyclic GMP.

J

DEFINITION:

Symbol for joule .

J

DEFINITION:

Symbol for joule .

J

DEFINITION:

Symbol for joule .

scale

DEFINITION:

1. A scheme or device by which some property may be evaluated or measured, such as a linear surface bearing marks at regular intervals, representing certain predetermined units, (e.g., a weighing instrument).
2. Either pan of a balance.
3. One of the small thin plates that cover the body especially of a fish or reptile.
4. A thin plate or flake.
5. A thin coating, layer, or incrustation.
6. To strip of scales.
7. A series of musical tones going up or down in pitch according to a specified scheme.

purification

DEFINITION:

The separating of foreign or contaminating elements from a substance of interest.

functional

DEFINITION:

1. Of or pertaining to a function.

2. Affecting the function but not the structure.

aquaporin-2

DEFINITION:

Also called WCH-CD, this water channel makes the principal cells of the inner medullary collecting duct in the kidneys more permeable to water. Lack of functional aquaporin-2 gene leads to a rare form of nephrogenic diabetes insipidus.

J

DEFINITION:

Symbol for joule .

gross

DEFINITION:

1. Large, macroscopic.

2. Taking no account of minutiae.

3. Glaringly noticeable; visible to the naked eye, as gross pathology.

4. Out-and-out, utter.

5. Bulky; especially, excessively fat.

6. General, broad.

7. Consisting of an overall total exclusive of deductions.

8. Carnal, earthy.

9. Coarse, unrefined; also, crudely vulgar.

10. Lacking knowledge.

putative

DEFINITION:

1. Commonly accepted or supposed.

2. Assumed to exist or to have existed.

binding

DEFINITION:

1. Wrapping with a binder or bandage.

2. Forming a weak, reversible chemical bond, e.g., antigen to antibody or hormone to receptor.

domain

DEFINITION:

A compact globular structure composed of one section of a polypeptide chain that constitutes a recognizable unit of the tertiary structure of a protein. Domains may fold up independently and maintain their native conformation when the connecting sections of the chain are broken.

C-terminus

DEFINITION:

The intracellular carboxy-terminus or tail of the vasopressin-2 receptor (V2R). See diagram.

AQP1

DEFINITION:

Aquaporin-1.

J

DEFINITION:

Symbol for joule .

G

DEFINITION:

As G - Symbol for "gauss," "giga-," "gravida," and "guanine" or "guanosine."

J

DEFINITION:

Symbol for joule .

J

DEFINITION:

Symbol for joule .

cloned

DEFINITION:

Propagated or copied.

aquaporin-1

DEFINITION:

Also known as CHIP-28, aquaporin-1 is the major water channel of the red blood cells. In the kidneys, it is involved in the reabsorption of most of the waste filtered through the glomerula.

cyclic GMP

DEFINITION:

Cyclic guanosine monophosphate.

aquaporins

DEFINITION:

A family of membrane channel proteins that serve as selective pores through which water crosses the plasma membranes of many human tissues and cell types.

proteins

DEFINITION:

Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen, and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc., and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, and in photosynthesis.

binding protein - any of a number of plasma proteins (See below) that bind to hormones of low solubility (chiefly the thyroid and steroid hormones), thus providing a transport system for them; some are specific for particular hormones, while others bind to any sparingly soluble hormones. Called also carrier protein or transport protein (See below).

carrier proteins - A binding protein (See above).

plasma proteins - The hundreds of different proteins present in blood plasma, including carrier proteins (such as albumin, transferrin, and haptoglobin), fibrinogen and other coagulation factors, complement components, immunoglobulins, enzyme inhibitors, precursors of substances such as angiotensin and bradykinin, and many other types of proteins.

transport protein - binding protein (See above).

cell membranes

DEFINITION:

Plasma membranes

aquaporin-2

DEFINITION:

Also called WCH-CD, this water channel makes the principal cells of the inner medullary collecting duct in the kidneys more permeable to water. Lack of functional aquaporin-2 gene leads to a rare form of nephrogenic diabetes insipidus.

AQP2

DEFINITION:

Aquaporin-2.

kidney collecting duct cells

DEFINITION:

Kidney collecting duct cells are cells which are mainly located in the medulla of the kidney. In the kidney, the blood fluid is filtered into tubules (nephrons) where electrolytes, water, and many other components are reabsorbed or even secreted. Collecting duct cells are at the end of such nephrons. Here, water is reabsorbed from the urine, and therefore, urine becomes concentrated. Reabsorption of water in collecting duct cells is regulated by the V2 vasopressin receptor. Inactivating mutations of V2 vasopressin receptor result in a loss of water reabsorption in collecting duct cells—the cause of nephrogenic diabetes insipidus (Schöneberg).

nephrogenic diabetes insipidus

DEFINITION:

A syndrome of polyuria and hyposthenuria caused by the failure of the renal tubules to reabsorb water in response to antidiuretic hormone, without disturbance in the renal filtration and solute excretion rates; the condition does not respond to exogenous vasopressin. It may be inherited as a rare X-linked trait or be acquired as a result of drug therapy or systemic disease.

NDI

DEFINITION:

Nephrogenic diabetes insipidus.

AQP2

DEFINITION:

Aquaporin-2.

presented

DEFINITION:

Having appeared or shown, as having appeared first at the os uteri (said of a fetus), or having appeared for examination, treatment, etc. (said of a patient).

aquaporin-1

DEFINITION:

Also known as CHIP-28, aquaporin-1 is the major water channel of the red blood cells. In the kidneys, it is involved in the reabsorption of most of the waste filtered through the glomerula.

AQP1

DEFINITION:

Aquaporin-1.

kidney

DEFINITION:

One of a pair of vertebrate organs situated in the body cavity near the spinal column that excrete waste products of metabolism, in man are bean-shaped organs about 4-1/2 inches long lying behind the peritoneum in a mass of fatty tissue, and consist chiefly of nephrons by which urine is secreted, collected, and discharged into a main cavity whence it is conveyed by the ureter to the bladder.

cells

DEFINITION:

See definitions for "cell."

putative

DEFINITION:

1. Commonly accepted or supposed.

2. Assumed to exist or to have existed.

binding

DEFINITION:

1. Wrapping with a binder or bandage.

2. Forming a weak, reversible chemical bond, e.g., antigen to antibody or hormone to receptor.

domain

DEFINITION:

A compact globular structure composed of one section of a polypeptide chain that constitutes a recognizable unit of the tertiary structure of a protein. Domains may fold up independently and maintain their native conformation when the connecting sections of the chain are broken.

C-terminus

DEFINITION:

The intracellular carboxy-terminus or tail of the vasopressin-2 receptor (V2R). See diagram.

AQP1

DEFINITION:

Aquaporin-1.

regulation

DEFINITION:

1. The act of adjusting or state or being adjusted to a certain standard.
2. In biology, the adaptation of form or behavior of an organism to changed conditions.
3. The power to form a whole embryo from stages before the gastrula.

protein

DEFINITION:

Any of a group of complex organic compounds which contain carbon, hydrogen, oxygen, nitrogen, and usually sulfur, the characteristic element being nitrogen, and which are widely distributed in plants and animals. Proteins, the principal constituents of the protoplasm of all cells, are of high molecular weight and consist essentially of combinations of a-amino acids in peptide linkages. Twenty different amino acids are commonly found in proteins, and each protein has a unique, genetically defined amino acid sequence which determines its specific shape and function. They serve as enzymes, structural elements, hormones, immunoglobulins, etc., and are involved in oxygen transport, muscle contraction, electron transport, and other activities throughout the body, and in photosynthesis.

binding protein - any of a number of plasma proteins (See below) that bind to hormones of low solubility (chiefly the thyroid and steroid hormones), thus providing a transport system for them; some are specific for particular hormones, while others bind to any sparingly soluble hormones. Called also carrier protein or transport protein (See below).

carrier proteins - A binding protein (See above).

plasma proteins - The hundreds of different proteins present in blood plasma, including carrier proteins (such as albumin, transferrin, and haptoglobin), fibrinogen and other coagulation factors, complement components, immunoglobulins, enzyme inhibitors, precursors of substances such as angiotensin and bradykinin, and many other types of proteins.

transport protein - binding protein (See above).