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United States Department of Agriculture

Agricultural Research Service

Title: Use of Video (Light) Microscopy and Low Temperature Scanning Electron Microscopy to Observe Identical Frozen Specimens

Authors
item Wergin, William
item Erbe, Eric
item Rango, Albert

Submitted to: Microscopy and Microanalysis
Publication Type: Proceedings
Publication Acceptance Date: July 15, 1998
Publication Date: N/A

Interpretive Summary: During the past 100 years, the light microscope combined with a camera has been used to photograph many different types of research samples. Because these photographs generally contain information about the internal and the external features of samples, they can be confusing. In spite of this problem, the photographs have contributed much research information to scientific areas that range from the descriptions of new organisms to the structure of crystals. Recently, a much newer and more powerful type of microscope called a scanning microscope also has been used to take more highly magnified photographs of samples. These photographs, which are more similar to those taken with an ordinary camera, show information only about the surface of a sample. Because of differences in information present in the photographs obtained with these two types of microscopes, scientists who have routinely used a light microscope are frequently confused when they begin to use a scanning microscope. To demonstrate and clarify this problem, a video (light) microscope was modified so that photographs of the same sample could be made with a light and a scanning microscope. This technique will be used by research scientists to distinguish internal structures from external structures and thereby help them interpret information that is obtained with these types of research microscopes.

Technical Abstract: During the past one hundred years, the light microscope (LM) in combination with the camera has been used to record numerous images of biological, as well as nonbiological, specimens. As a result, photomicrographs contributed a wealth of information to numerous disciplines that range from biosystematics to crystallography. The scanning electron microscope (SEM), which has been utilized in many biological fields during the last thirty years, has only recently been applied to other fields, such as hydrology and glaciology. The SEM provides increased resolution, greater depth of field, and images that characterize only the external surface features of a specimen. In contrast, LM photomicrographs recorded with transmitted or reflected light, frequently combine the external (surface) and internal features of a specimen into a single image. As a result, the LM images are more complex and can be difficult to interpret. To demonstrate and clarify this problem, a video (light) microscope was adapted so that photomicrographs and low temperature SEM micrographs of an identical frozen sample could be recorded and compared.

Last Modified: 4/18/2014
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