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【bio-news】来自休斯医学研究院的最新生命科学论
Gene Assigns ID Tags to Help Organize the Developing Brain
http://www.hhmi.org/news/zipursky20070921.html
The developing nervous system is a seemingly chaotic and exceedingly complex jumble of cells with specialized missions, unique architectures, and stereotyped patterns of neuronal connections, or synapses. How neurons' dendrites and axons weave themselves into precise neural circuits during development remains a challenging question in neurobiology. What are the molecular tags on the surface of neurons that allow them to distinguish between each other?
A single gene capable of producing more than 38,000 cell surface proteins is an essential tool in assuring the assembly of precise neural circuits in the fruit fly, Drosophila melanogaster. Now, two teams of researchers from the Howard Hughes Medical Institute (HHMI) have demonstrated how these closely related proteins establish the specificity that allows them to serve as identification tags for individual neurons.
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“Expanding from 11 to 19,000 is a bit of a stretch. So the question was, how many different binding specificities are there?” Prof. Zipursky said
Understanding the Neuron's Green Architecture
http://www.hhmi.org/news/ehlers20070920.html
Being green is a lifestyle. Turns out, each of your neurons is deeply committed to that green lifestyle - and you didn't even know it. In just a thousandth of a second, a neuron can dump up to 5,000 molecules of its chemical messenger - a neurotransmitter - into the synapse, where it will trigger an impulse in a neighboring nerve cell.
The neuron is a recycler par excellence when it comes to these neurotransmitters. Neurons must not only ready neurotransmitter receptors to receive the signals coming fast and furious, but they must also recycle receptors that have been used. And you thought you had recycling problems?
“This gives a tool to do experiments nobody has done before—exploring what happens when you no longer have recycling going on right next to the postsynaptic density.”
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“This gives a tool to do experiments nobody has done before—exploring what happens when you no longer have recycling going on right next to the postsynaptic density.”
Michael D. Ehlers
Stem Cells Derived from Adult Testes Produce Wide Range of Tissue Types for Therapeutic Organ Regeneration
http://www.hhmi.org/news/rafii20070920.html
After a decade of research, Howard Hughes Medical Institute scientists have succeeded in reprogramming adult stem cells from the testes of male mice into functional blood vessels and contractile cardiac tissue. The research offers a promising new source of stem cells for use in organ regeneration studies.
Some scientists think that organ-specific adult stem cells may offer the same therapeutic potential as embryonic stem cells, without the ethical concerns or the risk of immune rejection that are associated with embryonic stem cell therapies. However, adult stem cells may lack the plasticity and pluripotency of embryonic stem cells' capacity to generate any cell type. The study of adult stem cells has also been limited by their relative scarcity in various organs and the attendant difficulties in identifying and harvesting them, as well as differentiating them in large quantities into functional vascularized tissues.
“It appears that these specialized GPR125-positive spermatogonial cells could be an easily obtained and manipulated source of stem cells with a similar capability to form new tissues that we see in embryonic stem cells.”
Shahin Rafii
Natural Chemical Thwarts Estrogen's Heart Protection
http://www.hhmi.org/news/mangelsdorf20070916.html
In 2002, the National Institutes of Health stopped a large clinical trial when data revealed that women taking estrogen for symptoms of menopause had an increased risk of developing cardiovascular disease. New research suggests that higher risk may be partially explained by the presence of a naturally occurring chemical that blocks estrogen's protective effects on the heart.
The researchers theorize that women taking hormone replacement therapy may be at greater risk of developing heart disease because the chemical 27-hydroxycholesterol (27HC) inhibits the activity of estrogens circulating in the blood. 27-hydroxycholesterol is produced when the body breaks down cholesterol. Decreased estrogen, when combined with high cholesterol, atherosclerosis, or both, could lead to an increased risk of cardiovascular disease.
“Before this work, it was well known that estrogen may be cardioprotective. But the evidence was nil that there might be some endogenous antagonist to this protective system.”
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作者:admin@医学,生命科学 2011-07-22 05:11
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