Application Of Electron Tomography Research Articles

Nippotaenia mogurndae Yamaguti et Myiata, 1940 (Cestoda, Nippotaeniidea): first data on spermiogenesis and sperm ultrastructure.

Spermiogenesis and the spermatozoon ultrastructure of the cestode Nippotaenia mogurndae Yamaguti et Myiata, 1940 (Nippotaeniidea), a parasite of Perccottus glenii Dubowski, 1877 (Perciformes: Odontobutidae), have been investigated by means of transmission electron microscopy, cytochemical staining with periodic acid-thiosemicarbazide-silver proteinate (PA-TSC-SP) for glycogen, and electron tomography. The process of spermatozoon formation is characterised by the presence of (1) two centrioles without typical striated rootlets, (2) a single intercentriolar body, (3) a flagellar rotation (free flagellum plus flagellar bud), and (4) a complete proximodistal fusion. The mature spermatozoon of N. mogurndae contains a single helicoidal crested body, one axoneme of the 9 + "1" trepaxonematan structure, parallel cortical microtubules arranged in a ring in the anterior region of the cell, and a spiraled nucleus encircling the axoneme. Intracellular components are situated in a moderately electron-dense cytoplasm, containing glycogen in the principal regions (II, III, IV) of the spermatozoon. Application of electron tomography has revealed a helicoidal nature of the central electron-dense core in the central cylinder of the axoneme in parasitic cestodes for the first time. The patterns of spermiogenesis and spermatozoon ultrastructure resemble most closely those in mesocestoidids and may reflect the relationships between Nippotaeniidea and Mesocestoididae.

Single-particle analysis and electron tomography

Both single-particle analysis and electron tomography are special tools for the structural analysis of biological components by transmission electron microscopy. Single-particle analysis enables us to determine the structures of relatively large proteins and macromolecular complexes without crystallisation. Electron tomography is often used to visualise organelles and subcellular structures at molecular resolution. Recently, the scope of electron tomography has been widened due to the introduction of an automatic data collection system, cryo-electron microscopy, and improved sample preparation techniques. Application of electron tomography to single-particle analysis will be capable of analysing dynamics of large proteins. The techniques described in this review are expected to bridge the gap between the atomic resolution structures of protein molecules and cellular structures obtained by light microscopy.

Electron tomography of nanoparticle clusters: Implications for atmospheric lifetimes and radiative forcing of soot

Nanoparticles are ubiquitous in nature. Their large surface areas and consequent chemical reactivity typically result in their aggregation into clusters. Their chemical and physical properties depend on cluster shapes, which are commonly complex and unknown. This is the first application of electron tomography with a transmission electron microscope to quantitatively determine the three‐dimensional (3D) shapes, volumes, and surface areas of nanoparticle clusters. We use soot (black carbon, BC) nanoparticles as an example because it is a major contributor to environmental degradation and global climate change. To the extent that our samples are representative, we find that quantitative measurements of soot surface areas and volumes derived from electron tomograms differ from geometrically derived values by, respectively, almost one and two orders of magnitude. Global sensitivity studies suggest that the global burden and direct radiative forcing of fractal BC are only about 60% of the value if it is assumed that BC has a spherical shape.

Application of electron tomography to elucidate the 3D architecture of diverse asymmetric biological specimens

Electron tomography refers to the use of tomographic reconstruction methods to obtain three-dimensional (3D) information from transmission electron microscopy (TEM). This is accomplished by tilting the sample over a wide angular range with 180° being ideal, but 120° to 140° more typical due to limitations imposed by the geometry of most TEM specimens. If symmetry is present in the sample then the full angular range is not required. Furthermore, if the specimen is present as identical units, either in crystalline arrays or as single particles, the different tilts can be collected from different specimens and hence spare the total electron dose on any given particle. However, many important biological specimens are large, asymmetric objects which, due to their size, are not found as identical individual units. For such cases, the only recourse is to collect all the views from a single copy of the object, generally using a single axis tilt geometry.