• Z chromosome

    A sex chromosome in certain animals, such as chickens, turkeys, and moths. In humans, males are XY and females XX, but in animals with a Z chromosome, males are ZZ and females are WZ.

  • ZAP-70

    Zeta-chain-associated protein kinase 70. A member of the protein tyrosine kinase family, ZAP-70 is normally expressed in T cells and natural killer cells and has a critical role in the initiation of T-cell signaling. ZAP-70 is expressed in T cells and tumors of T-cell lineage. A high level of ZAP-70 expression appears restricted to T-cell […]

  • Zebra

    ‘When you hear hoof beats, think of horses, not zebras.’ For example, when someone develops a mild transient cough, a virus infection is the most logical and likely cause, and tuberculosis is a zebra.

  • Zygotic lethal gene

    A gene that is lethal (fatal) for the zygote, the cell formed by the union of a sperm (male sex cell) and an ovum (female sex cell). The zygote would normally develop into an embryo, as instructed by the genetic material within the unified cell. However, a zygotic lethal gene scotches prenatal development at its […]

  • Zygote intrafallopian transfer (ZIFT)

    A technique in which a woman’s egg is fertilized outside the body, then implanted in one of her fallopian tubes. This technique is one of the methods used to overcome infertility, the inability of couples to produce offspring on their own. First, the egg and the male sperm needed to fertilize it are harvested. Then […]

  • Disorder, central auditory processing

    Disorder, central auditory processing: A condition in which there is an inability to differentiate, recognize or understand sounds while both the hearing and intelligence are normal. (In technical terms, a central auditory processing disorder is a disease of the auditory pathways from the bulbar cochlear nuclei to the auditory cortex in the temporal lobe. Structures […]

  • SGPT

    Serum glutamic pyruvic transaminase, an enzyme that is normally present in liver and heart cells. SGPT is released into blood when the liver or heart are damaged. The blood SGPT levels are thus elevated with liver damage (for example, from viral hepatitis) or with an insult to the heart (for example, from a heart attack). […]

  • Xenograft

    A surgical graft of tissue from one species to an unlike species (or genus or family). A graft from a baboon to a human is a xenograft. The prefix “xeno-” means foreign. It comes from the Greek word “xenos” meaning stranger, guest, or host. (Xeno- and xen- are variant forms of the same prefix.)

  • Fibrosis, radiation

    Fibrosis, radiation: Scarring of the lungs from radiation. Radiation fibrosis is a consequence of the repair process that follows radiation pneumonitis (inflammation of the lungs due to radiation), as from radiation therapy. Radiation fibrosis typically occurs within months to a few years after the completion of radiation treatments. Whereas the inflammation of radiation pneumonitis is […]

  • Reproductive system

    In women, the organs that are directly involved in producing eggs and in conceiving and carrying babies; in men, the organs directly involved in creating, storing, and delivering sperm to fertilize an egg.