Tuesday, January 22, 2008

Uses Of Leech in this centuries

The medicinal leech Hirudo medicinalis has been used for centuries in the treatment of a variety diseases. The use of leeches for bloodletting reached its height in the eighteenth and early nineteenth centuries, and then began to give way to modern medicine. However, just when the leech was about to disappear from medical practice, new therapies using leeches emerged. Plastic surgeons have been using medicinal leeches to remove blood from post-operative occlusions, a procedure that increases the success of tissue transplants, reduction mammoplasty and the surgical re-attachment of amputated extremeties and digits by reducing the frequency of necrosis.

It has long been common knowledge that the host's blood continues to flow from the wound for a long time after the leech has ceased to feed. Indeed, it was shown a century ago (4) that extracts of the medicinal leech contain a substance, hirudin, which prevents blood clotting. Hirudin was isolated and characterized as a protein (5). The pharmacological effects of this potent anticoagulant in animals and in man (6, 7, 9) have also been extensively investigated. The advent of recombinant DNA technology opened the way to, and revived interest in the commercial production of hirudin.

Recombinant hirudin has been produced by major pharmaceutical companies and recent studies have shown that it effectively prevents thrombosis in several animal species and in man (9,10). The anticoagulant properties of hirudin are generally attributed to the inhibition of thrombin and consequently the blocking of fibrin formation. The beneficial effect of the medicinal leech of microsurgery, described above, could not, therefore, be due to hirudin, since thrombi in the microcirculation are usually due to platelet aggregation which is not inhibited by hirudin.

Apart from hirudin, saliva of the medicinal leech has been found to contain additional proteins, eglin, hyaluronidase, collagenase and apyrase (11, 12) and, in general, said publications (11, 12) disclose that leech saliva has platelet-aggregation inhibitory activity. Inhibition of platelet aggregation by leech saliva was also desceribed in references (13) and (14). Platelet aggregation inhibitory activity has been found also in the saliva of a number of blood-sucking anthropods, such as the bug Rhodnius prolixus (15) and the tick Ixodes dammini (16).