Tick anticoagulant peptide (TAP) is a novel inhibitor of blood coagulation factor Xa

Article Abstract:

In order to consume their meal of blood, ticks must keep the host's blood flowing while it is ingested. It is likely that factors in the saliva of blood-feeding organisms work against hemostasis (cessation of bleeding) by affecting platelet aggregation (clumping of cells involved in clot formation), coagulation (clot formation), and vascular contraction (which reduces blood flow). Factors that inhibit blood clotting have been identified in tick saliva. To better understand the anticoagulant action of tick saliva, the protein that inhibits factor Xa (a blood clotting factor) was purified from an extract of whole soft ticks (Ornithodoros moubata). This protein, tick anticoagulant peptide (TAP), was then investigated to determine its chemical properties. TAP inhibited the activity of factor Xa in a manner dependent on the concentration of TAP, and this inhibition was slow and specific for that clotting factor. Possible therapeutic applications of these findings could be the development of antibodies to the peptide, which would block feeding by the disease-carrying ticks, and use of TAP itself as an anticoagulant. (Consumer Summary produced by Reliance Medical Information, Inc.)

Anticoagulants (Medicine), Anticoagulants, Blood clotting, Blood coagulation, Ticks, Hematologic agents

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Platelet coagulation factor XIa-inhibitor, a form of Alzheimer amyloid precursor protein

Article Abstract:

Blood clotting proceeds in a cascade fashion by the activation of various zymogens (inactive enzymes), which then facilitate the next step of the coagulation process. Deficiency of factor XI, the inactive form of XIa, leads to excess bleeding of the mucosa and after surgery. Factor XIa normally activates factor IX. Platelets (blood cells essential for clotting) secrete a factor that inhibits factor XIa, as do cells of the cell culture line HepG2. Factor XIa-inhibitor was recovered and purified from these cells growing under laboratory conditions, and its properties were investigated. The inhibitor appeared the same as the inhibitor released from platelets, and seems to share much of its structure with amyloid precursor protein (APP), a protein found in the brains of patients with Alzheimer's disease, a progressive, debilitating disorder resulting in complete cognitive loss. The presence of the complete APP on the surface of many cells, and the fact that this inhibitor is released by platelets when they are stimulated, suggest that APP may play a role in coagulation. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abnormalities, Blood coagulation factors, Blood platelets

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What makes us tick?

Article Abstract:

Recent research suggests that metabolic rate and a genetic response to repair damage from again both factor in determining the life span of animals. The cloning and sequencing of a clock gene, clk-1, in the nematode Caenorhabditis elegans is discussed as well as other studies.

Aging, Physiological aspects, Genetic aspects, Caenorhabditis elegans, Biological rhythms, Biorhythms

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