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Bless the vampires, leeches, and other bloodsuckers!

Vlad the Impaler was his name, and impaling criminals was his game in old Transylvania. Only after being memorialized in fiction as Count Dracula did he become the vampire that has given the poor bat bad press ever since. That is now changing, however, as vampire bats, leeches, and other real bloodsuckers are beginning to find themselves in the limelight of modem medicine.

Some time ago, we reported on medical science's resurging interest in leeches and their ability to remove, painlessly and effectively, blood deposits just under the skin, produced by surgical and other trauma. Now, scientists are looking at the mechanism that permits these and similar creatures to obtain the blood meal they require for survival-the salivary material that prevents blood clots which would cut off their meal.

In vampire bats, for example, the salivary material is called plasminogen activator, or Bat-PA. Dr. Nils Bang of the Indiana University School of Medicine says, "It is remarkable that Bat-PA, along with proteins or peptides from leeches, snakes, and insects ... may come to assume major importance in cardiovascular drug development toward the end of the 20th century." His editorial in the July issue of Circulation, a journal of the American Heart Association, accompanies a report from scientists at Merck Sharp and Dohme Research Laboratories. The Merck group is experimenting with potential anticlotting compounds from several different exotic sources.

For several years, many hospital emergency rooms have used human tissue plasminogen activator TPA)-manufactured by recombinant DNA technology-to dissolve coronary artery blood clots in heart-attack victims. TPA, however, disappears rapidly from the blood, making it difficult to achieve adequate concentrations. The design of the Bat-PA molecule is such, however, that it lasts much longer in the blood. Researchers originally obtained small amounts of Bat-PA from South American Vampire bats, but it, too, is now being made in large quantities by the same technology.

A second article in the same journal, from the University of Virginia Health Sciences Center, reports on the use of hirudin, a clot-preventing enzyme produced by medicinal leeches. Scientists use the enzyme in experimental balloon angioplasty, a procedure that utilizes a tiny balloon to open up narrowed coronary arteries. Hirudin appears to keep the vessels opened much longer after surgery than has heretofore been possible in many cases.

The Merck scientists report that their work "is going well, but it is in its early stages." The Virginia scientists appear to be further along in their studies. Soon they will become part of a group of U.S. medical centers that will study the effects of combined treatment with hirudin and TPA in treating acute heart attacks.
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Title Annotation:medical research on usage of bat plasminogen activator in cardiovascular drug development
Publication:Medical Update
Date:Oct 1, 1991
Previous Article:When the shoe is on the other foot.
Next Article:Carotid cholesterol.

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