A normal gene which, when altered by mutation, becomes an oncogene that can contribute to cancer. Proto-oncogenes may have many different functions in the cell. Some proto-oncogenes provide signals that lead to cell division. Other proto-oncogenes regulate programmed cell death (apoptosis).
The defective versions of proto-oncogenes, known as oncogenes, can cause a cell to divide in an unregulated manner. This growth can occur in the absence of normal growth signals such as those provided by growth factors. A key feature of oncogene activity is that a single altered copy leads to unregulated growth.
- Proton magnetic resonance spectroscopic imaging
Magnetic resonance spectroscopic imaging.
A parasitic single-celled organism that can divide only within a host organism. For example, malaria is caused by the protozoa Plasmodium.
Toward the beginning, the nearer of two (or more) items. For example, the proximal end of the femur is part of the hip joint, and the shoulder is proximal to the elbow. The opposite of proximal is distal. For a more complete listing of terms used in medicine for spatial orientation, please see the entry […]
- Proximal white subungual onychomycosis
The rarest form of fungus infection of the finger or toenail. (Fungus infection of the finger or toenail is also called onychomycosis.) The infection begins in the nail fold (the portion of the nail opposite the tip of the finger). Proximal white subungual onychomycosis is typically associated with HIV infection (AIDS), though it can follow […]
- Proxy, health care
An advance medical directive in the form of a legal document that designates another person (a proxy) to make health care decisions in case a person is rendered incapable of making his or her wishes known. The health care proxy has, in essence, the same rights to request or refuse treatment that the person would […]