Adipose tissue: A type of connective tissue that
Adult stem cell: An undifferentiated cell found
in a differentiated tissue that can renew itself and (with
certain limitations) differentiate to yield all the specialized
cell types of the tissue from which it originated. (NIH)
Allogeneic cell transplantation: Transplantation
of cells from one individual to another of the same species.
Amniotic fluid: Fluid that fills the innermost
membrane, the amnion, that envelopes the developing embryo
Amnion: Innermost of the extra-embryonic membranes
enveloping the embryo in utero and containing the amniotic
Aneuploid: Having an abnormal number of chromosomes.
Angiogenesis: Development of new blood vessels.
A substance that, when introduced into the
body, stimulates the production of protein molecules called
antibodies that can bind specifically to the substance.
Astrocyte: A type of nerve cell that has supportive
and metabolic functions rather than signal conduction.
In transplantation, referring to a graft
in which the donor and recipient areas are in the same individual.
Autosome: Any chromosome other than a sex chromosome,
that is, any chromosome other than an X or a Y. (SMD)
Any of numerous unicellular microorganisms,
existing either as free living organisms or as parasites,
and having a broad range of biochemical, often pathogenic
used for an organism at the blastocyst stage of development.
(CR) (b) A preimplantation embryo of about 150 to 200 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). (NIH)
Blastocyst stage: An early stage in the
development of embryos, when (in mammals) the embryo is
a spherical body comprising an inner cell mass that will
become the fetus surrounded by an outer ring of cells that
will become part of the placenta. (CR)
The soft, fatty, vascular tissue that
fills most bone cavities and is the source of red blood cells
and many white blood cells.
Cardiomyoctes: Heart muscle cells.
Cartilage: A type of connective tissue that is
firm but resilient. It is found in joints and also as supportive
structure, for example in the ears.
Cell culture: Growth of cells in vitro on an artificial
medium for experimental research. (NIH)
A blood serum-like fluid that
bathes parts of the brain and the interior cavity of the spinal
Chromosomes: Structures inside the nucleus
of a cell, made up of long pieces of DNA coated with specialized
cell proteins, that are duplicated at each mitotic cell
division. Chromosomes thus transmit the genes of the organism
from one generation to the next. (CR)
Clone: A line of cells that is genetically identical
to the originating cell; in this case, a stem cell. (NIH)
Cord blood: Blood in the umbilical cord and placenta.
Cornea: Transparent tissue at the front of the
Cryopreserved embryos: Embryos, generally those
produced by in vitro fertilization exceeding the number
that can be transferred for uterine implantation, that have
Culture medium: The broth that covers cells in
a culture dish, which contains nutrients to feed the cells
as well as other growth factors that may be added to direct
desired changes in the cells. (NIH)
Dental pulp: The soft part inside a tooth, containing
blood vessels and nerves.
Diploid: Refers to the full complement
of chromosomes in a somatic cell, distinct for each species
(forty-six in human beings). (CR)
Diploid human cell: A cell having forty-six
Ectoderm: Upper, outermost layer of a group of cells derived
from the inner cell mass of the blastocyst; it gives rise
to skin nerves and brain. (NIH)
Edmonton protocol: A procedure (developed in Canada)
for transplanting pancreatic islet cells to the liver of
a patient with Type I diabetes.
Embryo: (a) 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. (NIH)
(b) The developing organism from the time of fertilization
until significant differentiation has occurred, when the
organism becomes known as a fetus. An organism in the early
stages of development. (CR)
Embryonic germ cells: Cells found in a specific
part of the embryo/fetus called the gonadal ridge that normally
develop into mature gametes. (NIH)
Embryonic stem cells: Primitive (undifferentiated)
cells from the embryo that have the potential to become
wide variety of specialized cell types. (NIH)
Embryonic stem cell line: Embryonic stem cells,
which have been cultured under in vitro conditions that
allow proliferation without differentiation for months to
Endoderm: Lower layer of a group of cells derived
from the inner cell mass of the blastocyst; it gives rise
to lungs and digestive organs. (NIH)
The mucous membranes lining the uterus.
Endothelial: relating to a flat layer of cells
lining the heart, for example, or blood vessels. (SMD)
Epidermal growth factor: A cell messenger protein
that has effects including stimulation of epidermal development,
in newborn animals it hastens eyelid-opening and tooth-eruption
Outside the body, frequently the equivalent
of "in vitro."
Fate (of cell progeny): The normal outcome of differentiation
of a cell's progeny.
Feeder layer: Cells used in co-culture to maintain
pluripotent stem cells. Cells usually consist of mouse embryonic
Fertilization: The process whereby male and female
gametes unite. (NIH)
Fetus: A developing human from usually two months
after conception to birth. (NIH)
Fibroblast: A stellate (star-shaped) or spindle-shaped
cell with cytoplasmic processes present in connective tissue,
capable of forming collagen fibers. (SMD)
cell (egg or sperm). (CR)
Gamma-interferon: A type of small protein with
antiviral activity, made by T lymphocytes.
Gastrulation: The process whereby the cells of
the blastocyst are translocated to establish three germ
layers. Also sometimes used to mark the end of the blastocyst
stage and the beginning of the next stage of embryonic development.
(Based on SMD)
Gene: A functional unit of heredity that is a segment
of DNA located in a specific site on a chromosome. A gene
directs the formation of an enzyme or other protein. (NIH)
Genome: The total gene complement of a set of chromosomes.
Germ cells (or primordial germ cells): A gamete,
that is, a sperm or egg, OR a primordial cell that can mature
into a sperm or egg. (NRC)
Germ layers: The three initial tissue layers arising
in the embryo-endoderm, mesoderm, and ectoderm-from which
all other somatic tissue-types develop. (NRC)
Gonad: An organ that produces sex cells (testes
or ovaries). (SMD)
Gonadal ridges: Embryonic structures arising in
humans at about five weeks, eventually developing into gonads
(either testes or ovaries).
Green Fluorescent Protein: A protein naturally
occurring in some animals including jelly fish that spontaneously
fluoresces. It can be used as a noninvasive marker in living
cells by attaching it to different proteins and then letting
it fluoresce so as to track the cell.
Haploid human cell: A cell such as an
egg or sperm that contains only twenty-three chromosomes.
Hematopoietic stem cell: A stem cell from which
all red and white blood cells develop. (NIH)
Hepatocyte: Liver cell.
Histocompatible: The immunological characteristic
of cells or tissue that causes them to be tolerated by another
cell or tissue; that allows some tissues to be grafted effectively
to others. (NRC)
Hurler syndrome: A heritable condition involving
deficiency of an enzyme (alpha-L-iduronidase), leading to
abnormal accumulations of materials inside cells, then resulting
in abnormal development of cartilage and bone and other
ICM cells: Cells from the inner cell mass, a population
of cells inside the blastula that give rise to the body
of the new organism rather than to the chorion or other
Unable to develop a normal immune
response to, for example, a foreign substance.
Immunosuppressive drugs: Drugs that prevent or
interfere with the development of an immunologic response.
After a transplant, immunosuppressive drugs are usually
necessary in order to prevent the recipient from rejecting
Implantation: The attachement of the blastocyst
to the uterine lining, and its subsequent embedding there.
(Based on SMD)
In vitro fertilization (IVF): The union
of an egg and sperm, where the event takes place outside
the body and in an artificial environment (the literal meaning
of "in vitro" is "in glass"; for example, in a test tube).
Inner cell mass: The cluster of cells inside the
blastocyst. These cells give rise to the embryonic disk
of the later embryo and, ultimately, the fetus. (NIH)
Karyotype: The chromosome characteristics (number,
shape, etc) of an individual cell or cell line, usually
presented as a systematized array in pairs. (SMD)
Leukemia inhibitory factor: A cell messenger protein
originally noted for inhibition of mouse M1 myeloid leukemia
cells that also has effects including inhibiting differentiation
to maintain stem cells.
The descendants of a common ancestor.
Long-term self-renewal: The ability of stem cells
to renew themselves by dividing into the same non-specialized
cell type over long periods (many months to years) depending
on the specific type of stem cell. (NIH)
A motile cell formed in tissues such
as the lymph nodes, that functions in the development of immunity.
Meiosis: A special process of cell division comprising
two nuclear divisions in rapid succession that result in
four cells (that will become gametes) with the haploid number
of chromosomes. (Based on SMD)
Mesenchymal stem cells: Cells from the immature
embryonic connective tissue. A number of cell types come
from mesenchymal stem cells, including chondrocytes, which
produce cartilage. (NIH)
Mesoderm: Middle layer of a group of cells derived
from the inner cell mass of the blastocyst; it gives rise
to.bone, muscle, and connective tissue. (NIH)
Metachromatic leukodystrophy: A heritable metabolic
disorder, usually of infancy, characterized by myelin loss
and other abnormalities of the white matter of the nervous
system, leading to progressive paralysis and mental retardation
or dementia. (SMD)
Mitochondria: Small, energy-producing organelles
Mitochondrial DNA: Genetic material inside the
mitochondria. Essentially all the mitochondria of an individual
come from the cytoplasm of the egg, so all mitochondrial
DNA is inherited through the maternal line.
Mitochondrial proteins: Proteins that are part
of the mitochondria.
Mitosis: Cell division, resulting in two cells
that each have the diploid number of chromosomes and are
just like the original cell.
Morphology: Configuration or structure, shape.
Mutagenicity: Tendency to promote mutations, that
is, genetic alterations.
As applied to stem cells, the ability
to differentiate into at least two, more differentiated descendant
Multipotent adult progenitor cells (MAPC): Cells
isolated from bone marrow that can be differentiated into
cells with characteristics of cartilage, fat, and bone.
Mycoplasma: A general category of microorganisms
that shares some characteristics of bacteria.
Natural killer cell: A cell type of the immune
system that destroys tumor cells and cells infected with
some types of organisms.
A part of the brain involved in detecting
and discriminating among different smells.
Oligodendrocyte: A type of neuroglia, that is,
a particular type of cell that is part of the nervous system
with supportive and metabolic functions rather than signal
conduction, this type forms the myelin sheath around nerve
Oocytes: Egg cells.
Osteogenesis imperfecta: A large and miscellaneous
group of conditions of abnormal fragility and plasticity
of bone, with recurring fractures on trivial trauma. (SMD)
Pancreas: An organ of the digestive system that
secretes the hormones insulin and glucagon, as well as digestive
Pancreatic beta cells: Cells of the pancreas (located
in pancreatic islets, or islets of Langerhans) that produce
Parkinson disease: A neurological syndrome usually
resulting from deficiency of the neurotransmitter dopamine
. . . ; characterized by rhythmical muscular tremors . .
The genetically and environmentally
determined physical characteristics of an organism.
Placenta: The oval or discoid spongy structure
in the uterus from which the fetus derives it nourishment
and oxygen. (NRC)
having great developmental plasticity,
as a pluripotent
stem cell. Cells that can produce
the cell types of the developing body, such as
the ICM cells of the blastocyst, are said to be pluripotent
Polarity: The property of having two opposite poles,
sides or ends (for example, humans have left-right polarity,
also front-back polarity and head-tailward polarity).
The number of times cells growing
in vitro have increased the total number of cells by a factor
of 2 compared to the initial number of cells. Primitive streak:
A band of cells appearing in the embryo at the start of the
third week of development, that marks the axis along which
the spinal chord develops.
Primordial germ cell: A gamete, that is, a sperm
or egg, OR a primordial cell that can mature into a sperm
or egg. (NRC)
Salivary gland: One of several pairs of glands
in the mouth that secrete saliva.
Skin biopsy: Process of removing tissue, in this
case skin, from living patients for diagnostic examination,
or the tissue specimen obtained by that process. (SMD)
A procedure pertaining to cells
in vitro in which the descendants of a single cell are physically
isolated from other cells growing in a dish, and then expanded
into a larger population.
Somatic cell nuclear transfer (SCNT): A method
of cloning: transfer of the nucleus from a donor somatic
cell into an enucleated egg to produce a cloned embryo.
Somite: One of the longitudinal series of segments
into which the body of many animals (including vertebrates)
is divided. (Merriam-Webster on line)
Stem cells: Stem cells are undifferentiated
multipotent precursor cells that are capable both of perpetuating
themselves as stem cells and of undergoing differentiation
into one or more specialized types of cells. (CR)
Stromal: Relating to the stroma of an organ or
other structure, that is, its framework, usually of connective
tissue, rather than its specific substance. (SMD)
The coming together of the egg and sperm
Thymus: An organ of the developing immune system,
active mainly in childhood.
T-lymphocyte: A cell type of the immune system
that matures in the thymus and is responsible for cell-mediated
Type-1A diabetes: A form of insulin dependent diabetes,
usually becoming evident in childhood, resulting from an
autoimmune reaction that destroys the pancreatic beta cells,
so that the body cannot produce its own insulin. In those
cases where the condition is not apparent until adulthood,
it is called latent autoimmune diabetes of adulthood. (LADA)
Specialized proteins that
bind to specific sites on DNA and turn on or turn off the
expression of different sets of genes.
Trophoblast: The extraembryonic tissue responsible
for implantation, developing into the placenta, and controlling
the exchange of oxygen and metabolites between mother and
Twinning: Development of monozygotic twins, that
is, when a very early embryo separates into two pieces,
each of which continues development, so that two embryos
actually come from one zygote.
Pertaining to the uterus.
Virus: A submicroscopic pathogen composed essentially
of a core of DNA or RNA enclosed by a protein coat, able
to replicate only within a living cell.
Xenotransplantion: A transplant of tissue from
an animal of one species to an animal of another species.
Zygote: The diploid cell that results
from the fertilization of an egg cell by a sperm cell. (CR)