Now, for the first time, University of Washington neurobiologists have interrupted this natural "annual remodeling" of the brain and have shown that there is a direct link between the death of old neurons and their replacement by newly born ones in a living vertebrate.
The scientists introduced a chemical into one side of sparrow brains in an area that helps control singing behavior to halt apoptosis, a cell suicide program. Twenty days after introduction of the hormones the researchers found that there were 48 percent fewer new neurons than there were in the side of the brain that did not receive the cell suicide inhibitor.
"This is the first demonstration that if you decrease apoptosis you also decrease the number of new brain cells in a live animal. The next step is to understand this process at the molecular level," said Eliot Brenowitz, a UW professor of psychology and biology and co-author of a new study. His co-author is Christopher Thompson, who earned his doctorate at the UW and is now at the Free University of Berlin.
"The seasonal hormonal drop in birds may mimic what is an age-related drop in human hormone levels. Here we have a bird model that is natural and maybe similar genes have a similar function in humans with degenerative diseases such as Alzheimer's and Parkinson's, as well as strokes, which are associated with neuron death."
The research involved Gambel's white-crowned sparrows, a songbird subspecies that winters in California and migrates to Alaska in the spring and summer to breed and raise its young. The sparrow's brain regions, including one called the HVC, which control learned song behavior in males, expand and shrink seasonally. Thompson and Brenowitz previously found that neurons in the HVC begin dying within four days hours after the steroid hormone testosterone is withdrawn from the bird's brains. Thousands of neurons died over this time.
In the new work, the UW researchers received federal and state permission to capture 10 of the sparrows in Eastern Washington at the end of the breeding season. After housing the birds for three months, they castrated the sparrows and then artificially brought them to breeding condition by implanting testosterone and housing them under the same long-day lighting conditions that they would naturally be exposed to in Alaska. This induced full growth of the song control system in the birds' brains.
Next the researchers transitioned the birds to a non-breeding condition by reducing the amount of light they were exposed to and removing the implanted testosterone. They infused the HVC on one side of the brain with chemicals, called caspase inhibitors, that block apoptosis, and two chemical markers that highlight mature and new neurons. Twenty days later the birds were euthanized and sections of their brains were examined under a microscope.
These procedures were done with the approval of the UW's Institutional Animal Care and Use Committee and the National Institute of Mental Health. The latter funded the research.
The HVC straddles both hemispheres of the brain but the two sides are not directly connected. When Thompson counted the number of newly born neurons that had migrated to the HVC, he found only several hundred of them among the hundreds of thousands of mature neurons he examined. And there were nearly half the number of new neurons in the side of the HVC where brain cell death was inhibited compared with the other, untreated side of the HVC. "This shows there is some direct link between the death of old neurons and the addition of new cells that were born elsewhere in the brain and have migrated," said Brenowitz. "What allows new cells to be incorporated into the brain is the big question. This is particularly true on a molecular level where we want to know what is the connection between cell death and neurogenesis and which genes are responsible."
The paper was published in a recent issue of the Journal of Neuroscience.
For more information, contact Brenowitz at 206-543-8534 or firstname.lastname@example.org
Joel Schwarz | EurekAlert!
A promising target for kidney fibrosis
21.04.2017 | Brigham and Women's Hospital
Stem cell transplants: activating signal paths may protect from graft-versus-host disease
20.04.2017 | Technische Universität München
More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.
Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...
Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.
"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...
The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.
Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...
The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...
Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.
Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...
20.04.2017 | Event News
18.04.2017 | Event News
03.04.2017 | Event News
24.04.2017 | Physics and Astronomy
24.04.2017 | Materials Sciences
24.04.2017 | Life Sciences