National Institutes of Health, Stem Cells: Scientific Progress and Future Research Directions, executive summary and chapter
1. On the web at http://stemcells.nih.gov/info/scireport/PDFs/frontmatter.pdf . The science behind the stem cell controversy in more detail.
· Stem cell: special kind of cell that has a unique capacity to renew itself and to give rise to specialized cell types
o Uncommitted to conduct a specific function until it receives a signal to develop into a specialized cell
· Pluripotent stem cells: have potential to develop into any cell type in the body
o Can be isolated from early human embryos
o Describes stem cells that can give rise to cells derived from all three embryonic germ layers (mesoderm, endoderm, ectoderm)
· Adult stem cell: undifferentiated cell that is found in a specialized tissue in the adult, such as blood
o Can yield specialized cell types of the tissue from which it originated
o Capable of self-renewal for the lifetime of the organism
o Found in bone marrow, blood stream, cornea and retina of eye, dental pulp of tooth, liver, skin, gastrointestinal tract, pancreas
o Unlike embryonic stem cells, there are no isolated adult stem cells that are capable of forming all cells of body (i.e. pluripotent)
§ Typically unipotent and give rise to just one cell type under normal conditions (process allows for steady state of self-renewal for tissue)
§ If tissue becomes damaged and replacement of multiple cell types is required, pluripotent stem cells may become activated to repair damage
· Why are long-term proliferation ability and pluripotency of embryonic stem cells and embryonic germ cells important?
o If cells are to be manipulated and used for transplantation, it is important to have sufficient quantities of cells that can be directed to differentiated into desired cell types and used to treat the many patients that may be suffering from a particular disease
· Types of research:
o Transplantation research: restoring vital body functions
§ Use to generate replacement tissues for treating neurological diseases
o Therapeutic delivery systems: stem cells as vehicle for delivery genes to specific tissues in the body
· Need a lot of basic research before direct patient application of stem cell therapies is realized
o Cells must be differentiated or otherwise modified before they can be used clinically
o In order to safely use stem cells or cells differentiated from them in tissues other than the tissue from which they were isolated, researchers will need purified populations (clonal lines) of adult stem cells
o Potential for recipient of stem cell transplant to reject these tissues as foreign is very high
§ May require modification to cells, to immune system, or both
· Embryonic and adult stem cells are different and present immense research opportunities for potential therapy
· Differentiated cells generated from both adult and embryonic stem cells can repair or replace damaged cells and tissues in animal studies.
The Next Pandemic?
Laurie Garrett
From Foreign Affairs, July/August 2005
Summary: Since it first emerged in 1997, avian influenza has become deadlier and more resilient. It has infected 109 people and killed 59 of them. If the virus becomes capable of human-to-human transmission and retains its extraordinary potency, humanity could face a pandemic unlike any ever witnessed.
Probably cause:
- confined to bird species, but may change
-killed 54% if the 109 cases of human contraction reported
-if evolving virus becomes capable of human-to-human transmission, “humanity could well face a pandemic unlike any ever witnessed”
-OR nothing will happen. Hence absolute uncertainty
-capacity to respond to global epidemic is severely imbalanced. international community will look to developed countries for support.
Oops:
-1976 One soldier died of swine flu and the secretary of health, edu, and welfare declared that there is evidence their will be a major flu epidemic in that upcoming fall.
-1918 flu virus killed 500,000 million people/. widely believed that influenza appeared in cycles and scientists believed the soldier incident sign for another wave of influenza pandemic.
-Ford asked congress to appropriate $135 million to vaccines production.
-but the swine flu never came—the consequences of being wrong about an epidemic so devastating that it was impossible to focus properly on the issue of likelihood.
Devolution:
-Understanding the risks of avian flu: originates with aquatic birds and pass on to domesticated birds.
-china annually raises 13 billion chickens. lagging behind on hygienic standards—favor rapid influenza evolution.
-when influenza successfully infects a new species it can switch from avian virus to mammalian one à human epidemic.
-by beginning of 2005 asian poultry industry lost nearly $15 billion
hard to kill:
-Hard to track: asians like to buy animals and kill them in the kitchen—hard to track where they got infected.
-but the majority infected have been young adults and children.
-otherwise healthy individuals infected—no scientific explanation for disease pattern.
-in event of pandemic vaccines will not be able to be produced fast enough. Too expensive anyways—can’t count on generosity of neighbors
-preferential access to vaccine and medications for troops. Social instability resulting from troop and policy losses acute.
-hospitals unable to cope with surge of new patients.
-even though scientists can’t tell leaders when influenza pandemic will occur, policy makers can’t afford to ignore the warning. [precautionary principle]
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