Three-Dimensional Analysis of Molecular Signals with Episcopic Imaging Techniques

Within the past decade it has become apparent that HVEM offers the biologist a means to explore the three-dimensional structure of cells and/or organelles. Stereo-imaging of thick sections (e.g. 0.25-10 μm) not only reveals anatomical features of cellular components, but also reduces errors of interpretation associated with overlap of structures seen in thick sections. Concomitant with stereo-imaging techniques conventional serial Sectioning methods developed with thin sections have been adopted to serial thick sections (≥ 0.25 μm). Three-dimensional reconstructions of the chondriome of several species of trypanosomatid flagellates have been made from tracings of mitochondrial profiles on cellulose acetate sheets. The sheets are flooded with acetone, gluing them together, and the model sawed from the composite and redrawn.The extensive mitochondrial reticulum can be seen in consecutive thick sections of (0.25 μm thick) Crithidia fasciculata (Figs. 1-2). Profiles of the mitochondrion are distinguishable from the anterior apex of the cell (small arrow, Fig. 1) to the posterior pole (small arrow, Fig. 2).

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In situ investigation of the primary recrystallization of alpha titanium in HVEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110313 ◽

1978 ◽

Vol 36 (1) ◽

pp. 634-635

Author(s):

S. Naka ◽

R. Penelle ◽

R. Valle

Keyword(s):

Dimensional Analysis ◽

Texture Evolution ◽

Cold Work ◽

Three Dimensional ◽

Primary Recrystallization ◽

Thin Foils ◽

In Situ Investigation ◽

Grain Growth Model ◽

Alpha Titanium

The in situ experimentation technique in HVEM seems to be particularly suitable to clarify the processes involved in recrystallization. The material under investigation was unidirectionally cold-rolled titanium of commercial purity. The problem was approached in two different ways. The three-dimensional analysis of textures was used to describe the texture evolution during the primary recrystallization. Observations of bulk-annealed specimens or thin foils annealed in the microscope were also made in order to provide information concerning the mechanisms involved in the formation of new grains. In contrast to the already published work on titanium, this investigation takes into consideration different values of the cold-work ratio, the temperature and the annealing time.Two different models are commonly used to explain the recrystallization textures i.e. the selective grain growth model (Beck) or the oriented nucleation model (Burgers). The three-dimensional analysis of both the rolling and recrystallization textures was performed to identify the mechanismsl involved in the recrystallization of titanium.

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Image formation analysis of thick biological specimens using three-dimensional power-spectra of through focus series

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168359 ◽

1994 ◽

Vol 52 ◽

pp. 124-125

Author(s):

Karen F. Han

Keyword(s):

Inelastic Scattering ◽

Imaging Techniques ◽

Mass Density ◽

Relative Proportion ◽

Three Dimensional ◽

Power Spectra ◽

Image Formation ◽

Energy Filtering ◽

Ewald Sphere ◽

Nonlinear Imaging

The primary focus in our laboratory is the study of higher order chromatin structure using three dimensional electron microscope tomography. Three dimensional tomography involves the deconstruction of an object by combining multiple projection views of the object at different tilt angles, image intensities are not always accurate representations of the projected object mass density, due to the effects of electron-specimen interactions and microscope lens aberrations. Therefore, an understanding of the mechanism of image formation is important for interpreting the images. The image formation for thick biological specimens has been analyzed by using both energy filtering and Ewald sphere constructions. Surprisingly, there is a significant amount of coherent transfer for our thick specimens. The relative amount of coherent transfer is correlated with the relative proportion of elastically scattered electrons using electron energy loss spectoscopy and imaging techniques.Electron-specimen interactions include single and multiple, elastic and inelastic scattering. Multiple and inelastic scattering events give rise to nonlinear imaging effects which complicates the interpretation of collected images.

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