A rule instituted by the US Food and Drug Administration (FDA) for the licensing of agents directed against diseases of low or no incidence. The two-animal rule states that, when agents such as an antibiotic or vaccine are needed for such diseases, these agents may be licensed if they meet two criteria. One criterion is that they show adequate protection against a deliberate challenge of infection in two species of animals, one being a non-rodent species. (This should ideally be a nonhuman primate.) And the other criterion is that the agent is safe in humans.
- Two-faced twins
Known medically as diprosopus, two-faced twins are conjoined twins (incompletely separated identical twins). The twins have almost complete fusion of their bodies with one set of limbs. Part or all of the face is duplicated. The condition usually results in stillbirth. The ancient two-faced Mexican figurines known as the “pretty ladies of Tlatilco” are now […]
Thromboxane A2, the active form of thromboxane.
Thromboxane B2, the inactive product of thromboxane.
Tylosis with esophageal cancer.
- Tylosis with esophageal cancer
A genetic disorder characterized by thickening (hyperkeratosis) of the palms and soles, white patches in the mouth (oral leukoplakia), and a very high risk of esophageal cancer. This is the only genetic syndrome known to predispose to squamous cell carcinoma of the esophagus. The risk of developing esophageal cancer is 95% by age 70. The […]