Untitled - D Ank Unlimited

plasmid 577 platelet antigens
plasmid
Extrachromosomal genetic structure that consists of a circular,
double-stranded DNA molecule that permits the host
bacterial cell to resist antibiotics and produce other effects
that favor its survival. Plasmid replication is independent of
the bacterial chromosome. Plasmids have been used widely
in recombinant DNA technology.
plasmin
A serine protease proteolytic enzyme in plasma generated
from its inactive precursor plasminogen. It is a
90-kDa enzyme that derives from cleavage of a single
arginyl–valyl bond in the C terminal region of plasminogen.
It consists of two unequal chains, termed heavy
(A) and light (B) chains, linked by a single disulfide
bond. The A chain derives from the N terminal region
of plasminogen. The B chain carries the serine active
site. Plasmin catalyzes the hydrolysis of fibrin; thus, it
facilitates the dissolution of intravascular blood clots. In
addition to its fibrinolytic activity, plasmin has numerous
other functions associated with coagulation, fibrinolysis,
and inflammation that include: (1) enhancement of antibody
responses to both thymus-dependent and thymusindependent
antigens, (2) augmentation of agglutination
by lectins, (3) facilitation of the escape of cells from
contact inhibition in culture, (4) enhancement of cytotoxicity
with or without participation of antibodies, and (5)
stimulation of B cell proliferation.
plasminogen
The inactive precursor of the proteolytic enzyme plasmin.
Several serine proteases such as urokinase convert
it to active plasmin. It is a β globulin widely distributed
in tissue, body fluids, and plasma and is a single-chain
monomeric molecule. Plasminogen activation occurs in
two stages. The GLU plasminogen activation begins with
removal of two peptides at the N terminus of the molecule
and conversion to Lys-plasminogen. The second step
involves the rapid conversion of Lys-plasminogen to
Lys-plasmin.
plasminogen activator
An enzyme produced by macrophages that converts plasminogen
to plasmin, which degrades fibrin.
IX
Ib
a
s s
β
Actin
binding
protein
Ic
IIa
β
Ic
IIa
a a
ss ss
Actin
filaments
platelet
A small (3 μm in diameter) round disk that is derived from
bone marrow megakaryocytes and is present in the blood.
Platelets function in blood clotting by releasing thromboplastin.
They also harbor serotonin and histamine, which
may be released during type I anaphylactic hypersensitivity
reactions. Complement receptor 1 (CR1) is present on the
platelets of mammals other than primates and is significant
for immune adherence. Activated platelets cluster to facilitate
blood clotting and release cytokines from preformed mRNAs
that affect leukocyte migration and function in inflammation.
platelet-activating factor (PAF)
A phospholipid with a molecular weight of about 300 to
500 Da formed by leukocytes, macrophages, mast cells, and
endothelial cells that induces aggregation of platelets and
promotes amine secretion, aggregation of neutrophils, release
of enzymes, and an increase in vascular permeability. Its effect
resembles that of IgE-mediated changes in anaphylaxis and
cold urticaria. It may also participate in endotoxin shock and is
derived from phosphorylcholine. The combination of antigen
with the Fab regions of antibody molecules bound through Fc
receptors to mast cells, polymorphonuclear leukocytes, and
macrophages results in platelet-activating factor (PAF) release.
PAF release accompanies anaphylactic shock and apparently
mediates inflammation and allergic reactions. PAF induces
a transient reduction in blood platelets, causes hypotension,
and facilitates vascular permeability, but it has no effects on
contracting smooth muscle and have no chemotactic activity.
Probably more than a single compound have this activity. PAF
is resistant to arylsulfatase B but is sensitive to phospholipases.
PAF may induce bronchoconstriction and vascular dilation and
leak and may serve as a significant mediator of asthma.
platelet antibodies
Refer to platelet antigens.
platelet antibodies, drug-induced
Amphotericin B, cephalothin, methicillin, pentamidine,
trimethoprim-sulfamethoxizole, and vancomycin may all
induce the synthesis of antiplatelet antibodies.
platelet antigens
Surface epitopes on thrombocytes that may be immunogenic,
leading to platelet antibody formation, which causes
such conditions as neonatal alloimmune thrombocytopenia
β
IIb
IIIa
IIIb
? Talin? ? ?
Schematic representation of principal platelet membrane glycoproteins indicating known or suspected complexes, disulfide bonds between chains,
calcium-bonding domains, and interactions with cytoskeletal components.
V
P