Bos taurus cattle. Mus musculus house mouse. Rattus norvegicus Norway rat. Gallus gallus chicken. Looking at the protein domains, we can see, for example, that the protein from chickens G. Considering that these domains reflect protein regions that have specific functional properties, we can infer that the chicken protein might carry out many of the same functions as the human BRCA1 protein. Thus, even though we might not think of chickens as being susceptible to breast cancer, their cells still likely need the chicken version of the BRCA1 protein to carry out DNA damage and repair processes in much the same way the human BRCA1 protein fulfills these tasks in human cells.
More about " conserved sequences ". Skip to main content. Enter the Course Modules University of Pennsylvania. About the Course Module. Enter the Course Module:. Because loss of neurons is usually permanent, scientists are working on two important strategies to help the brain after injury. One way is to protect the nervous system immediately after the damage occurs. This damage could be a stroke, a severe concussion, or any kind of injury. If we can somehow limit the number of neurons that die early after injury, then we are keeping the damage to a minimum.
To help with repair later on after the injury, after the damage is done, some scientists are trying to use stem cells as a treatment for neuronal loss in the brain.
They have the capacity to develop into brand new neurons if scientists treat them with special molecules. This is a little like elementary school students who are not doctors or plumbers yet, but they have the capacity to become any professional in the future, given the right training. The biggest challenge with replacing dead neurons with stem cells is to have these newcomer neurons integrate, or fit into, the existing brain networks the right way.
Looking at the structure of a neuron, you will notice it has a cell body and several arms that it uses to connect and talk with other neurons Figure 1 , left. The really long arm that sends signals to other neurons is called axon , and axons can be really long. If an axon is damaged along its way to another cell, the damaged part of the axon will die Figure 1 , right , while the neuron itself may survive with a stump for an arm.
The problem is neurons in the central nervous system have a hard time regrowing axons from stumps. Why do skin cells not have this problem? Skin cells are much simpler in structure. First, they need motivation. There are special molecules that help activate growth in neurons.
More of these motivating molecules are made when the neurons are active. So, if you keep your brain active, your neurons are more likely to grow. This is true both after injury and in the healthy brain. Some stop signs are part of the sheath, or covering, around neighboring axons, called myelin sheath Figure 1 , left. Some stop signs are part of a scar that gets built like a protective wall around an injury in an effort to keep the damage from spreading.
These scars are made by brain cells called astrocytes star cells, due to their star-like appearance. Scar-building astrocytes are just trying to help, but they also release a chemical into their environment that makes it hard for axons to grow Figure 2.
But, there is good news here as well. Scientists are working on strategies to motivate injured neurons to grow by using special growth molecules and to eliminate stop signs for axons in order to make the injury environment more supportive for nerve cell growth [ 1 ]. The immune response plays an essential role in any kind of repair after injury.
In injured skin, immune cells will rush to the site of injury from the blood and help the resident immune cells clean up debris from dead cells.
Once the clean up is done, the immune cells die and stop the fight. The brain has specialized resident immune cells as well, and they will become activated when they sense danger or damage.
If they continue to spit out toxic chemicals over long periods, they can cause more harm than good, by killing healthy neurons. This is why scientists are trying to understand what switches brain immune cells on and off and trying to figure out how they can modify the response of these immune cells, so the cells can be helpful rather than harmful [ 2 ]. The scientists further narrowed the 19 genes down to just 3 that could quickly and efficiently transform fibroblasts taken from either embryonic or young mice into nerve cells.
Tests showed that the newly transformed cells not only looked but also behaved like neurons. They formed functional connections, or synapses, with each other and with brain-derived neurons in a laboratory dish. The technique can now be studied to learn more about how cellular identities are determined and how they can be manipulated. Wernig and his colleagues are attempting to make similar conversions with human cells.
But they note that much more research is needed before this type of procedure could be considered for clinical use. Site Menu Home. Search Health Topics.
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