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Image processing in electron microscopy
163
Abstracts of the Israel Societ_v for Electrorl Microscopy
IMAGE PROCESSING Martin
IN ELECTRON
MICROSCOPY
Kessel
Dept. of Membrane Research, Hebrew Medical School,
and Ultrastructure University, Hadassah Jerusalem, Israel
Retrieval of the highest resolution information from electron micrographs of both biological and materials science specimens is critically dependent upon the combined use of optical and digital image processing. The foundations of image processing of electron micrograph images were laid down by Klug and Berqer in 1964 when they demonstrated that the micrograph of a periodic specimen could be used as the diffracting object in a simple optical bench and could reveal details of the periodicities in the specimen. It also became apparent that the optical diffraction pattern contained important information with regard to the defocus of the electron micrograph and the degree of astigmatism present. Methods soon became available for coding the pictorial information in digital form so that the reconstruction methodologies could be carried out in a Digitization also allowed computer. much greater versatility in various image processing operations. For example, using helical diffraction theory, DeRosier and Kluq in 1968 produced the first three-dimensional reconstruction of a biological object, the tail of bacteriophage T4. An important early application of image processing was the separation of confusing overlapping lattices by using filters in Fourier space to yield easily interpretable one-sided reconstructions. It soon became apparent, though, that the limiting factor in attaining high resolution was damage to the specimen due to interaction with the high-dosage electron beam. The requirement for extremely low electron dosages meant a poor signal-to-noise ratio which then required digital averaging procedures to recover the information. Both naturally occurring and laboratoryproduced two-dimensional crystals were studied and provided significant structural information. When the two-dimensional crystals were tilted in the electron microscope, Fourier synthesis was able to produce a three-dimensional reconstruction which allowed the structure to be seen in relation to its presumed biological function. The classic
example of this approach was the threedimensional reconstruction of bacteriorhodopsin by Unwin and Henderson in 1975. More recently, Frank and coworkers, using a methodology based on multivariate statistics, have produced reconstructions from averages of single particles such as the 30s ribosomal subunit from E. s. The orewaration of soecimens in vitrified iceLand their observation with excellent phase contrast at liquid nitrogen temperatures in the electron microscope has enabled a reduction in specimen damage as specimens are viewed in a natural aqueous environment. This is currently one of the most exciting fields of application in biological electron microscopy and has so far produced three-dimensional reconstructions of the gap junction, the acetylcholine receptor, ribosomal tetramers, actin filament, T4 bacteriophage tail, and matrix porin.
ENDOTHELIAL PINOCYTOTIC VESICLES AND THE PERMEABILITY OF CAPILLARIES IN HUMAN GLIOMAS S. Kohn, Faculty Haifa,
I. Nir and Y. Doron of Medicine, Israel
Technion,
The ultrastructure of the capillary endothelium was correlated with the uptake of Tc-99m pertechnetate as used in brain scintiqraphy. The uptake of Tc-99m pertechnetate was determined in seven qliomas. Three gliomas from the different qroups of uptake rates were quantitatively analyzed for pinocytotic activity. Pinocytotic activity was calculated as the mean ratio, R = (area of pinocytotic vesicles)/(area of endothelial cells). Capillaries of impermeable tumor had a low R value (0.0096) which was similar to that obtained in normal brain control (0.0091). In tumor with moderate uptake rates and in permeable tumor, the R values increased significantly (0.0343 and 0.0433, P < 0.05) by about 377% and 476%, respectively, as compared to that found in low-permeable tumor and in normal brain. Thus, a correlation appears to exist between the permeability of capillaries in gliomas and the pinocytotic vesiculation of the endothelial cells. Therefore, pinocytotic activity might be a factor in the uptake of radionuelides as revealed in the present
Abstracts of the Israel Societ_v for Electrorl Microscopy
IMAGE PROCESSING Martin
IN ELECTRON
MICROSCOPY
Kessel
Dept. of Membrane Research, Hebrew Medical School,
and Ultrastructure University, Hadassah Jerusalem, Israel
Retrieval of the highest resolution information from electron micrographs of both biological and materials science specimens is critically dependent upon the combined use of optical and digital image processing. The foundations of image processing of electron micrograph images were laid down by Klug and Berqer in 1964 when they demonstrated that the micrograph of a periodic specimen could be used as the diffracting object in a simple optical bench and could reveal details of the periodicities in the specimen. It also became apparent that the optical diffraction pattern contained important information with regard to the defocus of the electron micrograph and the degree of astigmatism present. Methods soon became available for coding the pictorial information in digital form so that the reconstruction methodologies could be carried out in a Digitization also allowed computer. much greater versatility in various image processing operations. For example, using helical diffraction theory, DeRosier and Kluq in 1968 produced the first three-dimensional reconstruction of a biological object, the tail of bacteriophage T4. An important early application of image processing was the separation of confusing overlapping lattices by using filters in Fourier space to yield easily interpretable one-sided reconstructions. It soon became apparent, though, that the limiting factor in attaining high resolution was damage to the specimen due to interaction with the high-dosage electron beam. The requirement for extremely low electron dosages meant a poor signal-to-noise ratio which then required digital averaging procedures to recover the information. Both naturally occurring and laboratoryproduced two-dimensional crystals were studied and provided significant structural information. When the two-dimensional crystals were tilted in the electron microscope, Fourier synthesis was able to produce a three-dimensional reconstruction which allowed the structure to be seen in relation to its presumed biological function. The classic
example of this approach was the threedimensional reconstruction of bacteriorhodopsin by Unwin and Henderson in 1975. More recently, Frank and coworkers, using a methodology based on multivariate statistics, have produced reconstructions from averages of single particles such as the 30s ribosomal subunit from E. s. The orewaration of soecimens in vitrified iceLand their observation with excellent phase contrast at liquid nitrogen temperatures in the electron microscope has enabled a reduction in specimen damage as specimens are viewed in a natural aqueous environment. This is currently one of the most exciting fields of application in biological electron microscopy and has so far produced three-dimensional reconstructions of the gap junction, the acetylcholine receptor, ribosomal tetramers, actin filament, T4 bacteriophage tail, and matrix porin.
ENDOTHELIAL PINOCYTOTIC VESICLES AND THE PERMEABILITY OF CAPILLARIES IN HUMAN GLIOMAS S. Kohn, Faculty Haifa,
I. Nir and Y. Doron of Medicine, Israel
Technion,
The ultrastructure of the capillary endothelium was correlated with the uptake of Tc-99m pertechnetate as used in brain scintiqraphy. The uptake of Tc-99m pertechnetate was determined in seven qliomas. Three gliomas from the different qroups of uptake rates were quantitatively analyzed for pinocytotic activity. Pinocytotic activity was calculated as the mean ratio, R = (area of pinocytotic vesicles)/(area of endothelial cells). Capillaries of impermeable tumor had a low R value (0.0096) which was similar to that obtained in normal brain control (0.0091). In tumor with moderate uptake rates and in permeable tumor, the R values increased significantly (0.0343 and 0.0433, P < 0.05) by about 377% and 476%, respectively, as compared to that found in low-permeable tumor and in normal brain. Thus, a correlation appears to exist between the permeability of capillaries in gliomas and the pinocytotic vesiculation of the endothelial cells. Therefore, pinocytotic activity might be a factor in the uptake of radionuelides as revealed in the present