Programmed cell death. Apoptosis is a type of cellular self-destruct mechanism that rids the body of damaged or aged cells. Unlike necrosis, a process in which cells that die as a result of acute injury swell and burst, spilling their contents over their neighbors and causing a potentially damaging inflammatory response, a cell that undergoes apoptosis dies in a neat and orderly fashion – shrinking and condensing, without damaging its neighbors. The process of apoptosis is often blocked or impaired in cancer cells. (May be pronounced “AY-pop-TOE-sis” OR “AP-oh-TOE-sis”.)

A test used in laboratory medicine, pharmacology, environmental biology, and molecular biology to determine the content or quality of specific components.

Two nitrogen-containing molecules (called nucleotides) that form the "rungs" of the ladder-like structure of DNA. The DNA in a single chromosome contains approximately 150 million base pairs. The number of base pairs within the telomere region of chromosomes are of particular relevance to the field of aging. The length of telomeres, distinct structures comprised of short, repetitive sequences of DNA located on the ends of chromosomes, ranges from 8,000 base pairs in a newborn to 3,000 base pairs in an adult and as low as 1,500 in elderly people. The average cell loses 30 to 200 base pairs from the ends of its telomeres each time it divides, contributing to (and serving as a marker of) aging.

A general term referring to cognitive decline that interferes with normal daily living. Dementia commonly occurs in older age and is characterized by progressive loss of memory, executive function, and reasoning. Approximately 70 percent of all dementia cases are due to Alzheimer’s disease.

Any of a group of complex proteins or conjugated proteins that are produced by living cells and act as catalyst in specific biochemical reactions.

A type of tumor that forms in the brain and spinal cord in neurons called glial cells. Roughly one-third of all brain tumors are gliomas. Malignant gliomas are highly aggressive, and survival rates for patients are poor, at roughly 10 percent after three years.^[1] A protein associated with human cytomegalovirus, a common beta-herpes virus, is expressed in more than 90 percent of gliomas.^[2]

An organism’s ability to maintain its internal environment within defined limits that allow it to survive. Homeostasis involves self-regulating processes that return critical bodily systems to a particular “set point” within a narrow range of operation, consistent with the organism’s survival.

A type of skin cancer. Melanomas typically form in the melanocytes, the pigment-producing cells located in the basal layer of the epidermis (skin). Melanomas commonly metastasize (spread) to other parts of the body. They account for approximately 10,000 deaths in the US each year.

An enzyme that facilitates the generation of complementary DNA. In viruses, reverse transcriptases convert viral RNA into a complementary DNA, which can then be integrated into the host’s genome. In humans, the reverse transcriptase telomerase maintains and extends the length of telomeres.

Senescence is a response to stress in which damaged cells suspend normal growth and metabolism. While senescence is vital for embryonic development, wound healing, and cancer immunity, accumulation of senescent cells causes increases inflammation and participates in the phenotype of aging.

Any type of cell that comprises an organism’s body. Somatic cells do not include gametes (sperm or egg), germ cells (cells that go on to become gametes), or stem cells.

A cell that has the potential to develop into different types of cells in the body. Stem cells are undifferentiated, so they cannot do specific functions in the body. Instead, they have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells. As such, they serve as a repair system for the body. Stem cells can divide and renew themselves over a long time. In 2006, scientists reverted somatic cells into stem cells by introducing Oct4, Sox2, Klf4, and cMyc (OSKM), known as Yamanaka factors.^[1]

An enzyme that extends the telomeres of chromosomes. Telomerase adds specific nucleotide sequences to the ends of existing chromosomes. Telomerase activity is highly regulated during development, and its activity is at an almost undetectable level of activity in fully developed cells. This lack of activity causes the cell to age. If telomerase is activated in a cell, the cell will continue to grow and divide, or become "immortal," which is important to both aging and cancer. Telomerase enzyme activity has been detected in more than 90 percent of human cancers.

Distinctive structures comprised of short, repetitive sequences of DNA located on the ends of chromosomes. Telomeres form a protective “cap” – a sort of disposable buffer that gradually shortens with age – that prevents chromosomes from losing genes or sticking to other chromosomes during cell division. When the telomeres on a cell’s chromosomes get too short, the chromosome reaches a “critical length,” and the cell stops dividing (senescence) or dies (apoptosis). Telomeres are replenished by the enzyme telomerase, a reverse transcriptase.