* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Why dread a bump on the head? June 2012 Lesson 5: What
Survey
Document related concepts
Nucleic acid double helix wikipedia , lookup
Epigenomics wikipedia , lookup
Polycomb Group Proteins and Cancer wikipedia , lookup
Genetic engineering wikipedia , lookup
Cell-free fetal DNA wikipedia , lookup
No-SCAR (Scarless Cas9 Assisted Recombineering) Genome Editing wikipedia , lookup
DNA supercoil wikipedia , lookup
Primary transcript wikipedia , lookup
Epigenetic clock wikipedia , lookup
Deoxyribozyme wikipedia , lookup
Molecular cloning wikipedia , lookup
DNA damage theory of aging wikipedia , lookup
Extrachromosomal DNA wikipedia , lookup
DNA vaccination wikipedia , lookup
Cre-Lox recombination wikipedia , lookup
Gel electrophoresis of nucleic acids wikipedia , lookup
Transcript
Why dread a bump on the head? Lesson 5: What happens to neurons after TBI? June 2012 Neurobiology Technique #1 ELECTROPHYSIOLOGY Neurobiology Technique #2 ANIMAL BEHAVIOR Electrophysiology is a way of observing and recording the electrical activity of cells. This is a particularly important technique for neuroscience, since neurons generate electrical signals in order to pass signals from one part of the body to another, or from one cell to another. There are many different electrophysiological techniques for different situations, but a basic technique involves inserting a very sharp, fine electrode directly into a single cell. This electrode measures electrical charge inside the cell, and how it changes over time. If an electrical signal passes through the cell, the charge measured by the electrode will rapidly change. Electrodes can also be placed near groups of cells, to measure changes in charge that happen when all the cells create electrical signals at the same time. These types of experiments can be done in living animals during surgical procedures where the skull is opened to give access to the brain. They can also be performed using slices of brain tissue that are kept alive for limited amounts of time. As cells in the slice begin to die, fewer and fewer cells will produce signals; only living cells will produce normal changes in electrical charge. Researchers may have many different reasons for observing and measuring the behavior of animals. Many experimental treatments, as well as illnesses and conditions, can affect the health and functioning of the brain. A natural consequence of changes in the brain is often an alteration in the behavior of the animal. Researchers can measure simple aspects of behavior, such as response to odors, lights, sounds, and other stimuli. Animals are often moved to a test environment where they can be easily observed or video-recorded. The animal is then exposed to the stimulus (the light, sound or other experience) and its response (startling, pricking ears, standing still) is noted. More complex tests of behavior include studying things like learning; for example, the animal might be trained to associate a stimulus with a reward of food, or a frightening event such as an unpleasant noise. The animal’s ability to respond in a normal way or be able to learn different associations can tell the researcher about the health of different regions of the brain, and whether those different regions are functioning properly. 1 Why dread a bump on the head? Lesson 5: What happens to neurons after TBI? June 2012 Neurobiology Technique #3 DNA Gel Electrophoresis Neurobiology Technique #4 Cell Culturing Researchers use gel electrophoresis to examine the length of DNA that they extract from biological material including brain tissue. This research method begins with DNA that has been extracted from a small piece of tissue that is removed from the organism being studied. The researcher inserts the DNA sample into holes in one end of a square block made of Jell-O-like material, called a “gel”. An electrical current is passed through the gel so it has a negatively charged side and positively charged side. The DNA, which has a negative charge, moves from where it starts (the negative side) in the gel toward the opposite (positive) side of the gel. As the DNA moves forward in a line through the gel, the fragments of DNA in the sample separate based on how long they are. After waiting a set amount of time, the researcher can see how far the fragments of DNA in the sample have traveled to estimate how long the pieces of DNA are. The ones that travelled the farthest are the smallest fragments of DNA. The DNA fragments that stayed nearest where they started are the longest pieces of DNA. Pieces of similar length will cluster together and make dark areas, called bands. The bands of DNA from the tissue sample are compared to bands created by DNA fragments of known lengths. In this way, the researcher can determine the lengths of the fragments in the DNA sample that was taken from the organism’s tissue. Cell culturing allows researchers to easily view properties of certain cell types that would be hard to see in a whole living organism or in pieces of tissue. A piece of tissue must be dissected from the organism and then processed quickly, so that the cells are not killed by the stress of being removed from the organism. The piece of tissue is treated with proteins or chemicals that can break down the substances that hold tissue together, so that the individual cells begin to separate out. The cells are then gently swirled so that they separate completely from each other. All of these steps must be done carefully, so that the cells are not damaged too much. The cells can then be transferred to a dish coated with proteins that help the cells attach to the surface, and a solution called growth medium is added. The growth medium contains the sugars, nutrients, oxygen and moisture that the cells would usually get from the blood, lymph or other fluid in the body needed to survive. The cultured cells can be kept for days or weeks, and can be examined and photographed or videotaped using a microscope to monitor any growth, change in shape, or response to experimental treatments that are added to the medium. However, even when great care is taken not to damage the cells during the culturing procedure, and with careful medium changes, the cells will gradually die, limiting the length of time during which experiments on these cells can be performed. 2 Why dread a bump on the head? Lesson 5: What happens to neurons after TBI? Technique Claim June 2012 Evaluating Neurobiology Techniques Evidence This technique WILL / WILL NOT #1 Provide additional evidence Electrophysiology about the occurrence of apoptosis and necrosis in brain tissue after TBI. This technique WILL / WILL NOT #2 Animal Behavior Provide additional evidence about the occurrence of apoptosis and necrosis in brain tissue after TBI. This technique #3 DNA Gel Electrophoresis WILL / WILL NOT Provide additional evidence about the occurrence of apoptosis and necrosis in brain tissue after TBI. This technique WILL / WILL NOT #4 Cell Culturing Provide additional evidence about the occurrence of apoptosis and necrosis in brain tissue after TBI. 3 Reasoning