platelet-derived growth factor

factor /fac·tor/ (fak´ter) an agent or element that contributes to the production of a result.

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accelerator factor  coagulation f. V.

angiogenesis factor  a substance that causes the growth of new blood vessels, found in tissues with high metabolic requirements and also released by macrophages to initiate revascularization in wound healing.

antihemophilic factor  (AHF)

1. coagulation f. VIII.

2. a preparation of factor VIII used for the prevention or treatment of hemorrhage in patients with hemophilia A and the treatment of von Willebrand disease, hypofibrinogenemia, and factor XIII deficiency, including preparations derived from human or porcine plasma or by recombinant technology.

antihemophilic factor A  coagulation f. VIII.

antihemophilic factor B  coagulation f. IX.

antihemophilic factor C  coagulation f. XI.

antinuclear factor  (ANF) see under antibody.

factor B  a complement component that participates in the alternative complement pathway.

B cell differentiation factors  (BCDF) factors derived from T cells that stimulate B cells to differentiate into antibody-secreting cells.

B lymphocyte stimulatory factors  (BSF) a system of nomenclature for factors that stimulate B cells, replacing individual factor names with the designation BSF and an appended descriptive code.

Christmas factor  coagulation f. IX.

C3 nephritic factor  (C3 NeF) an autoantibody that stabilizes the alternative complement pathway C3 convertase, preventing its inactivation by factor H and resulting in complete consumption of plasma C3; it is found in the serum of many patients with type II membranoproliferative glomerulonephritis.

coagulation factors  substances in the blood that are essential to the clotting process and hence, to the maintenance of normal hemostasis. They are designated by Roman numerals, to which the notation “a” is added to indicate the activated state. See also platelet f's .

factor I fibrinogen: a high-molecular-weight plasma protein converted to fibrin by the action of thrombin. Deficiency results in afibrinogenemia or hypofibrinogenemia.

factor II prothrombin: a plasma protein converted to thrombin by activated factor X in the common pathway of coagulation. Deficiency leads to hypoprothrombinemia.

factor III tissue thromboplastin: a lipoprotein functioning in the extrinsic pathway of coagulation, activating factor X.

factor IV calcium.

factor V proaccelerin: a factor functioning in both the intrinsic and extrinsic pathways of coagulation, catalyzing the cleavage of prothrombin to thrombin. Deficiency leads to parahemophilia.

factor VII proconvertin: a factor functioning in the extrinsic pathway of blood coagulation, acting with factor III to activate factor X. Deficiency, either hereditary or associated with vitamin K deficiency, leads to hemorrhagic tendency.

factor VIII antihemophilic factor (AHF): a storage-labile factor participating in the intrinsic pathway of blood coagulation, acting as a cofactor in the activation of factor X. Deficiency, an X-linked recessive trait, causes hemophilia A.

factor IX a relatively storage-stable substance involved in the intrinsic pathway of blood coagulation, activating factor X. Deficiency results in the hemorrhagic syndrome hemophilia B, resembling hemophilia A; it is treated with purified preparations of the factor, either from human plasma or recombinant, or with factor IX complex.

factor X Stuart factor: a storage-stable factor that participates in both the intrinsic and extrinsic pathways of blood coagulation, uniting them to begin the common pathway of coagulation; as part of the prothrombinase complex, activated factor X activates prothrombin. Deficiency may cause a systemic coagulation disorder. The activated form is called also thrombokinase.

factor XI plasma thromboplastin antecedent: a stable factor involved in the intrinsic pathway of blood coagulation, activating factor IX. Deficiency results in the blood-clotting defect hemophilia C.

factor XII Hageman factor: a stable factor activated by contact with glass or other foreign surfaces, which initiates the intrinsic process of blood coagulation by activating factor XI.

factor XIII fibrin-stabilizing factor: a factor that polymerizes fibrin monomers, enabling formation of a firm blood clot. Deficiency produces a clinical hemorrhagic diathesis.

colony-stimulating factors  a group of glycoprotein lymphokines, produced by blood monocytes, tissue macrophages, and stimulated lymphocytes and required for the differentiation of stem cells into granulocyte and monocyte cell colonies; they stimulate the production of granulocytes and macrophages and have been used experimentally as cancer agents.

factor D  a serine protease of the alternative complement pathway that cleaves factor B bound to C3b, releasing Ba while leaving Bb bound to C3b to form the C3 convertase C3bBb.

decay accelerating factor  (DAF) a protein of most blood cells as well as endothelial and epithelial cells, CD55; it protects the cell membranes from attack by autologous complement.

endothelial-derived relaxant factor , endothelium-derived relaxing factor (EDRF) nitric oxide.

extrinsic factor  cyanocobalamin.

F (fertility) factor  F plasmid.

fibrin-stabilizing factor  (FSF) coagulation f. XIII.

Fitzgerald factor  high-molecular-weight kininogen.

Fletcher factor  prekallikrein.

glucose tolerance factor  a biologically active complex of chromium and nicotinic acid that facilitates the reaction of insulin with receptor sites on tissues.

granulocyte colony-stimulating factor  (G-CSF) a colony-stimulating factor that stimulates the production of neutrophils from precursor cells.

granulocyte-macrophage colony-stimulating factor  (GM-CSF) a colony-stimulating factor that binds to stem cells and most myelocytes and stimulates their differentiation into granulocytes and macrophages.

growth factor  any substance that promotes skeletal or somatic growth, usually a mineral, hormone, or vitamin.

factor H  a glycoprotein that acts as an inhibitor of the alternative pathway of complement activation.

Hageman factor  (HF) coagulation f. XII.

histamine-releasing factor  (HRF) a lymphokine that induces the release of histamine by IgE-bound basophils in late phase allergic reaction.

homologous restriction factor  (HRF) a regulatory protein that binds to the membrane attack complex in autologous cells, inhibiting the final stages of complement activation.

factor I  a plasma enzyme that regulates both classical and alternative pathways of complement activation by inactivating their C3 convertases.

inhibiting factors  factors elaborated by one body structure that inhibit release of hormones by another structure; applied to substances of unknown chemical structure, while those of established chemical identity are called inhibiting hormones.

insulinlike growth factors  (IGF) insulin-like substances in serum that do not react with insulin antibodies; they are growth hormone–dependent and possess all the growth-promoting properties of the somatomedins.

intrinsic factor  a glycoprotein secreted by the parietal cells of the gastric glands, necessary for the absorption of vitamin B12. Lack of intrinsic factor, with consequent deficiency of vitamin B12, results in pernicious anemia.

LE factor  an antinuclear antibody having a sedimentation rate of 7S and reacting with leukocyte nuclei, found in the serum in systemic lupus erythematosus.

leukocyte inhibitory factor  (LIF) a lymphokine that prevents polymorphonuclear leukocytes from migrating.

lymph node permeability factor  (LNPF) a substance from normal lymph nodes which produces vascular permeability.

lymphocyte mitogenic factor  (LMF) a nondialyzable heat-stable macromolecule released by lymphocytes stimulated by a specific antigen; it causes blast transformation and cell division in normal lymphocytes.

lymphocyte transforming factor  (LTF) a lymphokine causing transformation and clonal expansion of nonsensitized lymphocytes.

myocardial depressant factor  (MDF) a peptide formed in response to a fall in systemic blood pressure; it has a negatively inotropic effect on myocardial muscle fibers.

osteoclast activating factor  (OAF) a lymphokine produced by lymphocytes which facilitates bone resorption.

factor P  properdin.

platelet factors  factors important in hemostasis which are contained in or attached to the platelets.

platelet factor 1 adsorbed coagulation factor V from the plasma.

platelet factor 2 an accelerator of the thrombin-fibrinogen reaction.

platelet factor 3 a lipoprotein with roles in the activation of both coagulation factor X and prothrombin.

platelet factor 4 an intracellular protein component of blood platelets capable of inhibiting the activity of heparin.

platelet activating factor  (PAF) an immunologically produced substance which is a mediator of clumping and degranulation of blood platelets and of bronchoconstriction.

platelet-derived growth factor  a substance contained in the alpha granules of blood platelets whose action contributes to the repair of damaged blood vessel walls.

R factor  see under plasmid.

releasing factors  factors elaborated in one body structure that cause release of hormones from another structure; applied to substances of unknown chemical structure, while those of established chemical identity are called releasing hormones.

resistance transfer factor  (RTF) the portion of an R plasmid containing the genes for conjugation and replication.

Rh factor , Rhesus factor genetically determined antigens present on the surface of erythrocytes; incompatibility for these antigens between mother and offspring is responsible for erythroblastosis fetalis.

rheumatoid factor  (RF) a protein (IgM) detectable by serological tests, which is found in the serum of most patients with rheumatoid arthritis and in other related and unrelated diseases and sometimes in apparently normal persons.

risk factor  a clearly defined occurrence or characteristic that has been associated with the increased rate of a subsequently occurring disease.

Stuart factor , Stuart-Prower factor coagulation f. X.

tissue factor  coagulation f. III.

transforming growth factor  (TGF) any of several proteins secreted by transformed cells and causing growth of normal cells, although not causing transformation.

tumor necrosis factor  either of two lymphokines that cause hemorrhagic necrosis of certain tumor cells but do not affect normal cells; they have been used as experimental anticancer agents. Tumor necrosis factor α (formerly cachectin ) is produced by macrophages, eosinophils, and NK cells. Tumor necrosis factor β, is lymphotoxin.

vascular endothelial growth factor  (VEGF), vascular permeability factor (VPF) a peptide factor that is a mitogen of vascularendothelial cells; it promotes tissue vascularization and is important in tumor angiogenesis.

von Willebrand's factor  (vWF) a glycoprotein that circulates complexed to coagulation factor VIII, mediating adhesion of platelets to damaged epithelial surfaces. Deficiency results in von Willebrand's disease.

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platelet-derived growth factor

n.

A substance in platelets that is mitogenic for cells at the site of a wound, causing endothelial proliferation.

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platelet

a small disk or platelike structure, the smallest of the formed elements in blood. Blood platelets (called also thrombocytes) are disk-shaped, non-nucleated blood elements with a very fragile membrane; they tend to adhere to uneven or damaged surfaces. They average about 250,000 per cubic millimeter of blood and are formed in the red bone marrow by fragmentation of megakaryocytes, the largest of the bone marrow cells. Platelet production is controlled by a hormone, thrombopoietin, and regulatory lymphocytes acting at the stem cell level. At any given time about one-third of the total blood platelets can be found in the spleen; the remaining two-thirds are in the circulating blood.

The functions of platelets are related to the clotting of blood. Because of their adhesion and aggregation capabilities platelets can occlude small breaks in blood vessels and prevent the escape of blood. Platelets which have adhered to exposed collagen in damaged vessels release ADP in milliseconds which in turn initiates the synthesis of thromboxane A₂, a very potent prostaglandin which causes platelet aggregation and localized vasoconstriction. Fibrinogen, factors V and VIII, calcium ions, platelet phospholipid (PF-3), associated with the platelet membrane are also released. Substances contained within the platelet granules such as thromboglobulin, heparin neutralizing activity (PF-4) mitogens such as platelet derived growth factor, thrombospondin, ADP, serotonin and calcium ions are also released by aggregated platelets.

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platelet-activating factor (PAF)

see platelet-activating factor.

platelet adhesion

the adherence of platelets to any area with damaged blood vessels; an important component of hemostasis.

platelet aggregation

the progressive accumulation of platelets, attracted by other platelets once adhesion begins. Thromboxane A₂ causes irreversible platelet aggregation.

platelet aggregation test

a known platelet aggregating factor such as collagen, ADP or thrombin is added to a suspension of the platelets under test and the degree of aggregation measured by decrease in turbidity of the suspension.

platelet count

may be performed directly (in a hemocytometer chamber) or indirectly (estimating from the stained blood smear by number per field or in comparison to the number of white blood cells), expressed as number of cells per liter of blood.

platelet-derived growth factor

one of three growth factors released by platelets which undergo the release reaction; the growth factors stimulate endothelial cell proliferation.

platelet distribution width (PDW)

an indication of variation in platelet size which can be a sign of active platelet release.

platelet factor 3 (PF-3) test, platelet release test

test the antiplatelet activity of serum; used to detect circulating antiplatelet antibodies. Antibody-antigen reactions involving platelets cause the release of PF-3 from platelets which in turn shortens the contact-activated clotting time of platelet-rich plasma (PRP).

platelet factors

factors important in hemostasis which are contained in or attached to the platelets: platelet factor 1 is adsorbed clotting factor V from the plasma; platelet factor 2 is an accelerator of the thrombin-fibrinogen reaction; platelet factor 3 is a phospholipid with potent procoagulant activity; platelet factor 4 is capable of inhibiting the activity of heparin (heparin neutralizing activity).

mean platelet volume (MPV)

elevated level is an indication of increased megakaryocyte shedding of platelets and decreased level is seen in thrombocytopenia.

platelet plug formation

see platelet aggregation (above).

platelet release reaction

measured by the degree of secondary ADP-mediated aggregation that occurs. This is assessed by the amount of PF-4, PF-3 or serotonin, etc. released.

platelet retention

tested by testing the adhesiveness of a suspension of the subject platelets to a glass bead column or standard size filter.

platelet rich plasma

plasma prepared by centrifugation to separate out red blood cells but not platelets for transfusion.

platelet storage-pool disease

an inherited autosomal thrombopathia in American foxhounds and cats characterized by a deficiency of platelet storage granules.

platelet transfusion

transfusion of fresh, nonchilled whole blood is the usual method of transfusing platelets to an animal with thrombocytopenia.