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Related Concept Videos

Role of Matrix Metalloproteases in Degradation of ECM01:23

Role of Matrix Metalloproteases in Degradation of ECM

Matrix metalloproteases (MMPs) are enzymes involved in the hydrolysis of proteins and glycoproteins of the extracellular matrix. MMPs are essential for the migration and proliferation of cells through the dense matrix network, throughout embryonic development, and throughout morphogenesis. The first MMP activity discovered was a collagenase in a tadpole's tail undergoing metamorphosis. The active collagen deposition and modifications lead to the morphogenesis of tadpoles into the adult body.
A...
Introduction to Hemostasis01:05

Introduction to Hemostasis

Hemostasis is a complex physiological process that prevents excessive bleeding when a blood vessel is injured. It's crucial for maintaining the integrity of the circulatory system, as it ensures that our blood remains fluid while still within the vascular network and yet clots to prevent blood loss upon vessel injury.
The three phases of hemostasis involve many clotting factors present in plasma and several substances released by platelets and injured tissue cells. It is a fast, localized, and...
Formation of the Platelet Plug01:22

Formation of the Platelet Plug

The platelet phase, the second stage of hemostasis, commences around 15-20 seconds after an injury. It follows and overlaps with the vascular phase, during which blood vessels constrict to minimize blood loss.
As the injured blood vessel contracts, endothelial cells undergo contraction, revealing collagen fibers in the basement membrane and underlying connective tissue. Furthermore, the plasma membrane of endothelial cells becomes adhesive, preparing the site for platelet adhesion. Platelets...
Extrinsic and Intrinsic Pathways of Hemostasis01:20

Extrinsic and Intrinsic Pathways of Hemostasis

Blood clotting or coagulation involves extrinsic and intrinsic pathways, which ultimately merge into the common pathway, forming a fibrin clot.
The Extrinsic Pathway
The extrinsic pathway of coagulation is typically initiated by tissue damage that exposes blood to tissue factor (TF), a protein released by the damaged tissue cells outside the blood vessels—this interaction with TF triggers biochemical reactions involving specific clotting factors. The key player here is Factor VII, which forms a...
Clot Retraction and Fibrinolysis01:16

Clot Retraction and Fibrinolysis

After a fibrin clot is formed, the next step is clot retraction, a vital process facilitated by platelet contractile proteins, such as actin and myosin. These proteins pull the fibrin strands closer together and condense the clot. This action reduces the size of the clot, creating a smaller, denser structure that effectively seals off the damaged vessel. Clot retraction consolidates the clot and helps with wound healing by bringing the edges of the damaged blood vessel closer together.

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Related Experiment Video

Updated: Jun 23, 2026

Platelet Adhesion and Aggregation Under Flow using Microfluidic Flow Cells
10:10

Platelet Adhesion and Aggregation Under Flow using Microfluidic Flow Cells

Published on: October 27, 2009

Human platelet collagenase.

C M Chesney, E Harper, R W Colman

    The Journal of Clinical Investigation
    |June 1, 1974
    PubMed
    Summary
    This summary is machine-generated.

    Platelets contain collagenase, an enzyme released during aggregation. This enzyme degrades collagen, potentially limiting blood clot formation through a negative feedback loop.

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    05:49

    Procoagulant Platelet Characterization by Measuring Phosphatidylserine Exposure and Microvesicle Release from Human Purified Platelets

    Published on: November 29, 2024

    Area of Science:

    • Biochemistry
    • Hematology
    • Enzymology

    Background:

    • Platelets contain proteolytic enzymes like cathepsin and elastase.
    • Collagen plays a crucial role in platelet aggregation.

    Purpose of the Study:

    • To investigate the presence and function of collagenase within platelets.
    • To understand the release mechanism and localization of platelet collagenase.

    Main Methods:

    • Assay of collagenase activity via hydrolysis of radiolabeled collagen.
    • Sub-cellular localization using sucrose density gradient analysis.
    • Assessment of collagenolytic activity in gel-filtered platelets and plasma.

    Main Results:

    • Collagenase is liberated from platelets by aggregating agents (epinephrine, ADP, collagen).
    • Activity appears early in aggregation, not as part of the release reaction.
    • Collagenase is found in both granule and membrane fractions.
    • Plasma inhibitors, including alpha(1)-antitrypsin, affect collagenolytic activity.
    • Platelet collagenase degrades collagen and reduces its aggregation-promoting capacity.

    Conclusions:

    • Platelets possess collagenase activity.
    • This enzyme is released upon activation and localized in granules and membranes.
    • Platelet collagenase may regulate thrombus formation by degrading collagen.