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ACS News Service Weekly PressPac: Wed Sep 13 16:42:03 EDT 2006

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News Items in this Edition

Adult stem cells show wider potential than previously thought

Chemists are developing new insights and techniques in an effort to expand the therapeutic potential of stem cells, which includes possible treatments for Parkinson’s disease, diabetes, spinal cord injury and other devastating conditions.

Embryonic stem cells are the most versatile stem cells, capable of being transformed into any other cell type, depending on their desired therapeutic use. Now, researchers at Northwestern University have found new evidence that hematopoietic stem cells, a type of adult stem cell derived from the bone marrow that gives rise to blood cells, are capable of undergoing more diverse transformations than previously thought and could be transformed into a wide variety of tissue types, not just blood cells.

In recent laboratory tests, human megakaryocytes (bone marrow cells that produce blood platelets that are responsible for blood clotting) derived from adult hematopoietic stem cells were, for the first time, reprogrammed into neutrophil-like cells similar to the white blood cells that are responsible for fighting infections, according to study leader E. Terry Papoutsakis. Insights from this study could help guide similar adult stem cell transformations in other cell types in the future, he says.

Elasticity of tissue environment plays role in determining stem cell growth

Researchers at the University of Pennsylvania have shown that the elasticity of a stem cell’s environment is a major determinant of what type of tissue the stem cell becomes.

In laboratory tests, Dennis Discher and Adam Engler grew mesenchymal stem cells (derived from adult bone marrow) in polymer hydrogels with either soft, medium or rigid elasticity. Based on resulting cell shapes as well as messenger RNA and protein markers, stem cells grown in softer environments — such as brain tissue — tended to produce nerve-like cells; those grown in environments with medium elasticity — similar to muscle — produced muscle-like cells

The stem cells grown in more rigid environments — like bone — produced bone-like cells. The study provides new clues on how chemical and mechanical factors interact to influence stem cell growth, the researchers say.

‘Stretched’ stem cells have potential to be transformed into blood vessel cells

Scientists have searched for years for a renewable cell source to craft blood vessels that can be used for heart bypass surgery and perform more like natural arteries.

Now, researchers at the University of California, Berkeley, have shown that mesenchymal stem cells from adult bone marrow can be repeatedly and mechanically stretched — in a manner similar to a taffy pull — into patterns that could potentially transform them into smooth muscle cells similar to blood vessel tissue.

These newly formed smooth muscle cells, which can expand and contract, could be used as a component of a tissue-engineered graft that may provide superior performance over conventional grafts that are used for bypass surgery, says study leader Kyle Kurpinkski, a doctoral candidate in the University’s Department of Bioengineering.

California scientists find natural way to control spread of destructive Argentine ants

Chemists and biologists at the University of California, Irvine, (UCI) think they may have found a natural way to finally check the spread of environmentally destructive Argentine ants in California and elsewhere in the United States: Spark a family feud.

Organic chemist Kenneth Shea, evolutionary biologist Neil Tsutsui and graduate student Robert Sulc found that the ants use chemical cues on their exoskeletons to recognize other members of their own colony. Because Argentine ants in the California super colony are so interrelated, they have similar “recognition” cues and generally cooperate with each other.

But in their preliminary laboratory work, Shea and Tsutsui were able to create a slightly altered, synthetic version of one of these “recognition” compounds, which was composed mainly of linear hydrocarbons with one- to three-side chains called methyl groups. When coated onto experimental Argentine ants, the synthetic recognition compound caused untreated nest mates to attack. Although further study is needed, this approach could help control the spread of this pest, Shea said.

Argentine ants are one of the most widespread and ecologically damaging invasive species, Tsutsui said. When Argentine ants are introduced to a new habitat, they eliminate virtually all native species of ants and cause significant harm to agricultural crops, such as citrus, by protecting aphids and scale insects from potential predators and parasites.

Pesticide exposure could increase risk of early onset of Parkinson’s disease

Low-level exposure to a banned but lingering pesticide appears to accelerate changes in the brain that can potentially lead to the onset of Parkinson’s disease symptoms years or even decades before they might naturally develop, researchers have found in a pilot study.

The concept of an accelerated disease process is a new twist in the investigation of the long-suspected link between the use of pesticides and Parkinson’s disease, according to Gary Miller and colleagues. They found that levels of dieldrin, a now-banned organochlorine pesticide developed in the 1940s as an alternative to DDT, were three times higher in the brains of 14 people who had Parkinson’s disease than in the brains of 12 people without the disease.

Based on this finding, the researchers estimated the lifetime exposure levels of these people and extrapolated these levels to mice. They then exposed laboratory mice to low, but “environmentally relevant” dosages of dieldrin ― about 1 to 3 milligrams per kilogram. After one month, although none of the mice showed symptoms of Parkinson’s disease, the researchers did detect increased levels of oxidative stress in the brain and significantly reduced uptake of dopamine, the neurotransmitter that plays a key role in the development of Parkinson’s.

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