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Adult Stem Cell
An adult stem
cell is an undifferentiated (unspecialized) cell that occurs in a
differentiated (specialized) tissue, renews itself, and
becomes specialized to yield all of the specialized cell types
of the tissue from which it originated. Adult stem cells are capable
of making identical copies of themselves for the lifetime of the
organism. This property is referred to as “self-renewal.” Adult stem
cells usually divide to generate progenitor or precursor
cells, which then differentiate or develop into “mature” cell types
that have characteristic shapes and specialized functions. Often
they are difficult to identify, isolate, and purify. There are
insufficient numbers of cells available for transplantation and
adult stem cells do not replicate indefinitely in culture. |
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Blastocyst
A
preimplantation embryo of 30-150 cells. The blastocyst consists of
a sphere made up of an outer layer of cells (the trophectoderm), a
fluid-filled cavity (the blastocoel), and a cluster of cells on the
interior (the inner cell mass). |
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Differentiation
The
process whereby an unspecialized early embryonic cell acquires the
features of a specialized cell such as a heart, liver, or muscle
cell. |
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Embryo
In
humans, the developing organism from the time of fertilization until
the end of the eighth week of gestation, when it becomes known as a
fetus. |
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Embryonic stem (ES) cells
Primitive
(undifferentiated) cells from the embryo that have the potential to
become a wide variety of specialized cell types. |
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Graft-versus-host disease (GVHD)
A
condition that occurs following bone marrow transplantation in which
the donor-derived T cells attack the host’s tissues. |
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In vitro
Literally,
“in glass;” in a laboratory dish or test tube; an artificial
environment. |
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In vivo
In
the living subject; in a natural environment. |
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Pluripotent Stem Cell
A single
pluripotent stem cell has the ability to give rise to types of cells
that develop from the three germ layers (mesoderm, endoderm, and
ectoderm) from which all the cells of the body arise. The only known
sources of human pluripotent stem cells are those isolated and
cultured from early human embryos and from fetal tissue that was
destined to be part of the gonads. |
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Stromal cell
A non-blood cell that is derived from blood organs,
such as bone marrow or fetal liver, which is capable of supporting
growth of blood cells in vitro. Stromal cells that make this matrix
within the bone marrow are also derived from mesenchymal stem cells. |
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T Cells
A type of white blood cell that is of crucial
importance to the immune system. Immature T cells migrate to the
thymus gland in the upper chest cavity, where they mature and
differentiate into various types of T cells and become active in the
immune system in response to a hormone called thymosin and other
factors. T cells that are potentially activated against the body’s
own tissues are normally killed or changed (“down-regulated”) during
this maturation process. |
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Teratoma
A tumor composed of tissues from the three embryonic germ layers.
Usually found in ovary and testis. Produced experimentally in
animals by injecting pluripotent stem cells, in order to determine
the stem cells’ abilities to differentiate into various types of
tissues. |
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Tissue culture
Growth of tissue in vitro on an artificial medium for experimental
research. |
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Tolerance
A
state of specific immunologic unresponsiveness. Individuals are
normally tolerant to their own cells and tissues. Autoimmune
diseases occur when tolerance fails. |
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Xenotransplantation
Cross species transplantation (e.g. pig to human tissue
transplantion) |
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