glossary
adult stem cells
Derived from the umbilical cord and placenta or from blood, bone marrow, skin, and other tissues.
altered nuclear transfer (ANT)
Altered Nuclear Transfer would be similar to SCNT; the key difference being that the resulting cells should carry a mutation that causes cell death at the blastocyst stage, thereby never having the potential to develop into a full embryo and thus avoiding the ethical issues with use of embryos.
astrocytes
Once inside the brain or spinal cord, neural progenitor cells grow into neuron-supporting stem cells called astrocytes.
bioreactor
An apparatus, such as a large fermentation chamber, for growing organisms such as bacteria or yeast that are used in the biotechnological production of substances such as pharmaceuticals, antibodies, or vaccines, or for the bioconversion of organic waste.
blastocyst
A very young embryo that contains 200 to 250 cells and is shaped like a hollow sphere.
chimera
Named after the mythical Greek creature with a lion's head, a goat's body and a serpent's tail, a chimera is a mixture of two or more genetically distinct tissues in a single organism, produced as a result of organ transplant, grafting, or genetic engineering.
Human chimeras are not unnatural. For example, most mothers carry some cells from each of their children in their blood and most twins carry some cells from their sibling twins. Recipients of organs donated by other humans are chimeras and if you have had a heart valve replaced by a valve from a pig or a cow you are an animal-human chimera. Also, for many years now, scientists have been putting human genes into bacteria and farm animals in order to make useful human proteins such as the hormone insulin.
dedifferentiation
The mechanism by which cells of some animals (newts, etc.) revert back to an undifferentiated state. Researchers are attempting to replicate the process in humans.
differentiation
The process by which cells or tissues undergo a change toward a more specialized form or function, especially during embryonic development.
ectoderm
The outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue, and, in vertebrates, sense organs develop.
endoderm
The innermost of the three primary germ layers of an animal embryo, developing into the gastrointestinal tract, the lungs, and associated structures. Also called hypoblast.
fusiform
Tapering at each end; spindle-shaped.
hemopoietic stem cells (HSCs)
Stem cells found in the bone marrow. Hemopoiesis is the formation of blood cellular components.
hypoblast
See endoderm.
mesenchymal stem cells
Stem cells from which connective tissue, bone, cartilage, and the circulatory and lymphatic systems develop. Mesenchymal stem cells are found in the mesenchyme, the part of the embryonic mesoderm that consists of loosely packed, fusiform or stellate unspecialized cells.
mesoderm
The middle embryonic germ layer, lying between the ectoderm and the endoderm, from which connective tissue, muscle, bone, and the urogenital and circulatory systems develop.
neural progenitor cells
Specialized neural stem cells that arise from primitive stem cells during the first few weeks of human brain development. Unlike embryonic stem cells, they can only develop into neural tissue and they are incapable of living forever, as embryonic stem cells can. But the neural progenitor cells are much more appropriate for clinical use because, unlike embryonic stem cells, they can grow in the absence of animal derivatives that are considered a potential source of contamination.
olfactory ensheathing glia (OEG)
OEG are a promising regenerative therapy for spinal cord injury. OEG are very unusual cells that normally reside in the olfactory nerve and bulb, the organs that carry olfactory information to the brain. The olfactory nerve is the only cranial nerve that continuously regenerates in adult mammals. This ability has been credited to the presence of these cells. At least half a dozen laboratories have now reported that these cells will facilitate functional neural regeneration when transplanted to the brain or spinal cord.
pluripotent
Having the ability to differentiate into any of several types of cells.
somatic cell nuclear transfer (SCNT)
In SCNT, a nucleus from a patient's body cell, such as a skin cell, is introduced into an unfertilized egg from which the original genetic material has been removed. The egg is then used to produce a blastocyst whose stem cells could be used to create tissue that would be compatible with that of the patient. This is called therapeutic cloning. Its advocates say the process does not result in the creation--or destruction--of human life because the egg is never fertilized or implanted in a uterus, as it would be in reproductive cloning.
stellate
Arranged or shaped like a star; radiating from a center.
stem cell
An unspecialized cell that gives rise to a specific specialized cell, such as a blood cell. They serve as the natural repair system for the human body. There are many different types of stem cells; not all of them arise from embryos.
theraputic cloning
see somatic cell nuclear transfer
xenotransplantation
The transplantation, implantation, or infusion into a human recipient of either (a) live cells, tissues, or organs from a nonhuman animal source, or (b) human body fluids, cells, tissues or organs that have had ex vivo contact with live nonhuman animal cells, tissues or organs.