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Stem Cells

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Stem Cells Human Stem Cell Research (embryonic and somatic) What are Embryonic Stem Cells? They re the blastomeres in the blastocyst Blastocyst Reached after ... – PowerPoint PPT presentation

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Title: Stem Cells


1
Stem Cells
  • Human Stem Cell Research (embryonic and somatic)

2
What are Embryonic Stem Cells?
  • Theyre the blastomeres in the blastocyst

3
Blastocyst
  • Reached after four to six days (hatches from
    the zona pellicuda)
  • Lasts approximately until the implantation in the
    uterus
  • Upon implantation, a hormone (hCG) notifies the
    mother's body that she is pregnant, preventing
    menstruation
  • Little later, leads to gastrulation (approx. two
    weeks or so later)
  • Gastrulation is the start of the restricted
    (biological) definition of embryo
  • http//www.nhmrc.gov.au/embryos/information/_files
    /humanembryo.pdf

4
Mammalian (Human) Embryogenesis What is an
embryo?
  • The embryo of a placental mammal is defined as
    the organism between the first division of the
    zygote (a fertilized ovum) and the time until it
    becomes a fetus.
  • In humans, the embryo is defined as the product
    of conception from implantation in the uterus
    through the eighth week of development.
  • An embryo is called a fetus at a more advanced
    stage of development and up until birth or
    hatching.
  • In humans, this is from the eighth week of
    gestation.

5
NIH Definitions
  • Stem cells - have the ability to divide for
    indefinite periods in culture and to give rise to
    specialized cells. Stem cells are cells that
    divide by mitosis to form either
  • two stem cells, thus increasing the size of the
    stem cell "pool",
  • Or
  • one daughter that goes on to differentiate, and
  • one daughter that retains its stem-cell
    properties.
  • Pluripotent Stem Cells - capable of giving rise
    to most tissues of an organism.
  • Multipotent Stem Cells capable of giving rise
    to cells that have a particular function.
  • Totipotent Cells - have the capacity to form an
    entire organism (e.g., the fertilized egg).
  • First four or so cells produced by cleavage of
    the fertilized egg are also totipotent.
  • Cannot make more of themselves in mammals (no
    mammalian totipotent stem cells).
  • Totipotent cells have the capacity to specialize
    into extraembryonic membranes and tissues, the
    embryo, and all postembryonic tissues and organs.

6
Totipotent vs. Pluripotent Stem Cells
7
Embryonic Stem Cell vs Embryonic Germ Cell lines
  • Embryonic Stem Cells
  • From In-Vitro Fertilized embryos
  • Embryonic Germ Cells
  • From Aborted Fetuses

8
What are Embryonic Stem Cells?
9
Start with the Animal Embryo
10
Sources of Embryonic Stem cells
  • Embryonic Stem cell lines
  • Excess embryos from In-Vitro Fertilization
    clinics
  • Embryos created for research by IVF
  • Therapeutic cloning

Reproduced by permission of the NIH
11
Reproductive Cloning vs. Therapeutic Cloning
  • Purpose of therapeutic cloning is to harvest
    Embryonic Stem cells for treatment
  • ? blastocyst destroyed
  • Purpose of reproductive cloning is to make new
    person
  • ? blastocyst implanted in uterus

Reproduced by permission of the NIH
12
What about Adult (Somatic) Stem Cells?
  • Some Stem Cells live in the body of humans.
  • Most of these cells are Multipotent.
  • Multipotent Stem Cells can only be induced to
    become fewer tissues than Pluripotent Stem cells
    that are derived from Embryos.
  • New research is showing that we can induce adult
    stem cells to become more pluripotent.

13
Sources and Targets
14
Pluripotent Blood Stem Cells
15
Potential Benefits
  • Organ shortage (long term)
  • Tissues for Treatments (shorter term)
  • Valves, Skin, Nerves for Spinal Cord Injuries
  • Diabetes (Type 1)

16
Stem Cell Uses
17
Patient Specific Stem Cell Therapy
18
Promise of Stem Cell Research
19
Challenges
20
Major Ethical Issues
  • For those who believe that the embryo has the
    moral status of a person from the moment of
    conception, research (or any other activity) that
    would destroy the embryo is considered wrong and
    should not take place.
  • For those who believe otherwise, arriving at an
    ethically acceptable policy in this arena
    involves a complex balancing of a number of
    important ethical concerns.
  • Although many of the issues remain contested on
    moral grounds, they co-exist within a broad area
    of consensus upon which public policy can, at
    least in part, be constructed.
  • ETHICAL ISSUES IN HUMAN STEM CELL RESEARCH VOLUME
    I Report and Recommendations of the National
    Bioethics Advisory Commission Sept 1999

21
Bibliography
  • ETHICAL ISSUES IN HUMAN STEM CELL RESEARCH VOLUME
    I Report and Recommendations of the National
    Bioethics Advisory Commission National Bioethics
    Advisory Commission Sept 1999
  • Berg, Paul Biochem 118 Lecture Stanford
    University http//cmgm.stanford.edu/biochem118/Ste
    m20Cell.html Accessed 1/17/2005
  • Human Stem Cell Research Promise and Problems
    http//www.northwestern.edu/science-outreach/stemc
    ell/stemcells.html Accessed 1/17/2005
  • Picture at the top http//science.howstuffworks.co
    m/brain1.htm
  • National Institutue of Health http//stemcells.nih
    .gov/info/basics/basics4.asp
  • http//easyweb.easynet.co.uk/sfl/rlb_stem.htm
    drawn image
  • http//www.tracy.k12.ca.us/thsadvbio/ppt/Promise2
    0and20Peril20of20Stem20Cells.ppt
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