Blood Groups and Transfusions

Lamb blood was used in early blood transfusion experiments, which date from the late 1600s. By the 1800s, human blood was being used. Results were unpredictable— some recipients were cured, but some were killed when their kidneys failed under the strain of handling clumping red blood cells when blood types were incompatible. So poor was the success rate that, by the late 1800s, many nations banned transfusions.

Around this time, Austrian physician Karl Landsteiner began investigating why transfusions sometimes worked and sometimes did not. In 1900, he determined that blood was of differing types and that only certain combinations of them were compatible. In 1910, identification of the ABO blood antigen gene explained the observed blood type incompatibilities. Today, twenty

The Return of the Medicinal Leech

It had taken surgeon Joseph Upton ten hours to sew the five-year-old's ear back on, after a dog had bitten it off. At first the operation appeared to be a success, but after four days, trouble began. Blood flow in the ear was blocked. Close examination showed that the arteries that the surgeon had repaired were fine, but the smaller veins were becoming congested. So Dr. Upton tried an experimental technique — he applied twenty-four leeches to the wound area.

The leeches latched on for up to an hour each, drinking the boy's blood. Leech saliva contains several biochemicals, one of which is a potent anticoagulant called hirudin in honor of its source, the medicinal leech Hirudo medicinalis. Unlike conventional anticlotting agents such as heparin, which are short-acting, hirudin works for up to twenty-four hours after the leech has drunk its fill and dropped off. Hirudin specifically blocks thrombin in veins. The long-acting leech biochemical gave the boy's ear time to heal.

Leeches have long been part of medical practice, with references hailing back to the ancient Egyptians 2,500 years ago (fig. 14B). The leech's popularity peaked in Europe in the nine teenth century, when French physicians alone used more than a billion of them a year, to drain "bad humours" from the body to cure nearly every ill. Use of leeches fell in the latter half of the nineteenth century. They were rediscovered by Yugoslav plastic surgeons in 1960 and by French microsurgeons in the early 1980s. In 1985, Dr. Upton made headlines and brought leeches into the limelight by saving the boy's ear at Children's Hospital in Boston.

A leech's bite does not hurt, patients say. But for those unwilling to have one or more 3-inch long, slimy green-gray invertebrates picnicking on a wound, hirudin is also available as a drug called hirulog, produced by recombinant DNA technology (fig. 14C). ■

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Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

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