| Stem cells are primal cells common to all
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| | culture conditions can alter the behavior
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| multi-cellular organisms that retain the
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| | of cells, making it unclear whether the
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| ability to renew themselves through cell
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| | cells will behave in a similar manner in
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| division and can differentiate into a
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| | vivo. Considerable debate exists whether
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| wide range of specialized cell types.
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| | some proposed adult cell populations are
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| Research in the human stem cell field
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| | truly stem cells.
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| grew out of findings by Canadian
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| | • Totipotent stem cells are produced
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| scientists Ernest A. McCulloch and James
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| | from the fusion of an egg and sperm cell.
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| E. Till in the 1960s.
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| | Cells produced by the first few divisions
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| A stem cell is a primitive type of cell
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| | of the fertilized egg are also
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| that can be coaxed into developing into
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| | totipotent. These cells can differentiate
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| most of the 220 types of cells found in
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| | into embryonic and extraembryonic cell
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| the human body (e.g. blood cells, heart
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| | types.
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| cells, brain cells, etc). Some
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| | • Pluripotent stem cells are the
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| researchers regard them as offering the
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| | descendants of totipotent cells and can
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| greatest potential for the alleviation of
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| | differentiate into cells derived from the
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| human suffering since the development of
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| | three germ layers.
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| antibiotics. Over 100 million Americans
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| | • Multipotent stem cells can produce
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| and two billion other humans worldwide
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| | only cells of a closely related family of
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| suffer from diseases that may eventually
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| | cells.
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| be treated more effectively with stem
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| | • Unipotent cells can produce only one
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| cells or even cured. These include heart
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| | cell type, but have the property of
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| disease, diabetes, and certain types of
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| | self-renewal which distinguishes them
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| cancer.
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| | from non-stem cells.
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| Stem cells can be extracted from very
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| | Treatments
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| young human embryos -- typically from
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| | Medical researchers believe that stem
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| surplus frozen embryos left over from
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| | cell therapy has the potential to
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| in-vitro fertilization (IVF) procedures
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| | radically change the treatment of human
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| at fertility clinics. A couple undergoing
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| | disease. A number of adult stem cell
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| IVF is faced with four alternatives for
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| | therapies already exist, particularly
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| their 16 or so surplus embryos:
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| | bone marrow transplants that are used to
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| There are very few parents willing to
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| | treat leukaemia. In the future, medical
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| give their embryos to another couple for
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| | researchers anticipate being able to use
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| a variety of emotional reasons. There are
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| | technologies derived from stem cell
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| very few couples willing to receive them
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| | research to treat a wider variety of
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| for emotional reasons and because thawed
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| | diseases including cancer, parkinson's
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| embryos have such a low chance of
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| | disease, spinal cord injuries, and muscle
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| starting a pregnancy. Preservation can be
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| | damage, amongst a number of other
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| expensive.
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| | impairments and conditions. However,
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| Stem cell properties
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| | there still exists a great deal of social
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| These properties can be illustrated in
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| | and scientific uncertainty surrounding
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| vitro, using methods such as clonogenic
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| | stem cell research, which could possibly
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| assays, where the progeny of single cell
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| | be overcome through public debate and
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| is characterized. However, in vitro
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| | future research.
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