Morphometric analysis of electron micrographs have demonstrated that diameters of
fibrin strands follow a bimodal distribution comprising a major network of thicker
fibres with a minor network interspersed and made up of very fine fibres. The relationship
between the two networks is not fixed and invariant. It will be shown that the two
networks are highly responsive to changes in the physiological conditions of clotting.
Such a system has biological adaptability and tends to result in fibrin which is more
suited to serve its varying roles in haemostasis, in limiting sepsis, in promoting
neovascularization and in acting as a scaffolding for wound repair.
The response of the two network system to dextran, an agent widely used and well known
for its antithrombotic properties, has been examined. It will be shown that in vitro
dextran increases fibrin fibre thickness, reduces permeability and tensile strength
of networks developed in plasma. Similar changes were found to follow when dextran
is infused in clinical dosage in man. It was found that the increase in the thickness
of major network fibre is at the expense of protein in the minor network. Such means
of modulating distribution of fibrin fibre diameter within fibrin networks provide
a new approach to antithrombotic prophylaxis.
