scholarly journals THE FORM AND STRUCTURE OF KINETOPLAST DNA OF CRITHIDIA

1972 ◽  
Vol 54 (2) ◽  
pp. 346-364 ◽  
Author(s):  
Hartmut C. Renger ◽  
David R. Wolstenholme
Keyword(s):  
Electron Microscopy ◽  
Cesium Chloride ◽  
Contour Length ◽  
Main Band ◽  
Thin Sections ◽  
Group A ◽  
Linear Molecules ◽  
Different Strains ◽  
Topological Interlocking

Cesium chloride centrifugation of each of the DNAs extracted from eight strains of Crithidia revealed a main band at ρ = 1.717 g/cm3 and a satellite band varying from ρ = 1.701 to 1.705 g/cm3 for the different strains By electron microscopy each DNA was shown to include circular molecules, 0.69–0.80 µ in mean contour length, and large, topologically two-dimensional masses of DNA in which the molecules appeared in the form of rosettes. DNA isolated from kinetoplast fractions of Crithidia acanthocephali was shown to consist of light satellite DNA and to be mainly in the form of large masses, 0.8 µ (mol wt = 1.54 x 106 daltons) circular molecules, and a few long, linear molecules. The results of experiments involving ultracentrifugation, heating, and quenching, sonication, and endodeoxyribonuclease digestion, combined with electron microscopy, are consistent with the following hypothesis. The large DNA masses are associations of 0.8 µ circles which are mainly covalently closed. The circles are held together in groups (the rosettes) of up to 46 by the topological interlocking of each circle with many other circles in the group. A group of circles is attached to an adjacent group by one or more circles, each interlocking with many circles of both groups. Each of the associations comprises, on the average, about 27,000 circles (total mol wt ≃ 41 x 109 daltons). A model is proposed for the in situ arrangement of the associations which takes into consideration their form and structure, and appearance in thin sections

scholarly journals Three-dimensional electron microscopy of ribosomal chromatin in two higher plants: a cytochemical, immunocytochemical, and in situ hybridization approach.

1991 ◽  
Vol 39 (11) ◽  
pp. 1495-1506 ◽  
Author(s):  
P M Motte ◽  
R Loppes ◽  
M Menager ◽  
R Deltour
Keyword(s):  
Electron Microscopy ◽  
In Situ Hybridization ◽  
Spatial Organization ◽  
Higher Plants ◽  
Three Dimensional ◽  
Spatial Arrangement ◽  
Thin Sections ◽  
Cytoplasmic Dna ◽  
Immunocytochemical Techniques

We report the 3-D arrangement of DNA within the nucleolar subcomponents from two evolutionary distant higher plants, Zea mays and Sinapis alba. These species are particularly convenient to study the spatial organization of plant intranucleolar DNA, since their nucleoli have been previously reconstructed in 3-D from serial ultra-thin sections. We used the osmium ammine-B complex (a specific DNA stain) on thick sections of Lowicryl-embedded root fragments. Immunocytochemical techniques using anti-DNA antibodies and rDNA/rDNA in situ hybridization were also applied on ultra-thin sections. We showed on tilted images that the OA-B stains DNA throughout the whole thickness of the section. In addition, very low quantities of cytoplasmic DNA were stained by this complex, which is now the best DNA stain used in electron microscopy. Within the nucleoli the DNA was localized in the fibrillar centers, where large clumps of dense chromatin were also visible. In the two plant species intranucleolar chromatin forms a complex network with strands partially linked to chromosomal nucleolar-organizing regions identified by in situ hybridization. This study describes for the first time the spatial arrangement of the intranucleolar chromatin in nucleoli of higher plants using high-resolution techniques.

Ultrastructure of the in situ adherence of Mobiluncus to vaginal epithelial cells

1988 ◽  
Vol 34 (6) ◽  
pp. 757-766 ◽  
Author(s):  
Jan M. De Boer ◽  
Friso H. F. Plantema
Keyword(s):  
Electron Microscopy ◽  
Epithelial Cell ◽  
Epithelial Cells ◽  
Cell Surface ◽  
Bacterial Vaginosis ◽  
Vaginal Fluid ◽  
Thin Sections ◽  
Epithelial Cell Surface ◽  
Curved Rods

From patients with bacterial vaginosis motile, anaerobic, comma-shaped bacteria can be isolated, which have recently been placed into the new genus Mobiluncus. In this study, electron microscopy was used to examine the in situ adherence of these motile curved rods to detached epithelial cells (comma cells) in vaginal fluid from two patients with bacterial vaginosis. Thin sections showed that the curved rods attached both directly to the epithelial cell surface and at various distances from it. It is concluded that after initial attachment these motile bacteria can grow at the epithelial cell surface in sessile microcolonies. Ruthenium red staining demonstrated a coating of precipitated glycocalyx material both on the surface of the curved rods and on their flagella. This may indicate that in situ the adherent curved rods were enclosed in a very hydrated matrix of exopolysaccharides. Conspicuous was the ability of the curved rods to attach to the epithelial cell surface via their cell tips. However, in situ no specialized bacterial cell surface structures were seen that might explain this polar attachment. Electron microscopy of pure cultures demonstrated that both Mobiluncus curtisii subsp. curtisii and Mobiluncus mulieris can produce a glycocalyx in vitro.

New Insights on the Morphology of Nanocomposite Prepared by In Situ Emulsion Polymerization

2015 ◽  
Vol 775 ◽  
pp. 170-175
Author(s):  
José Costa de Macêdo Neto ◽  
João Evangelista Neto ◽  
Nayra Reis do Nascimento ◽  
Sheila Contant ◽  
Liliane Maria Ferrareso Lona
Keyword(s):  
Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
Nanocomposite Powder ◽  
Thin Sections ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Level Of Details ◽  
High Level

In order to better understand the morphology and properties of polymer nanocomposites it is necessary to conduct their characterization by Transmission Electron Microscopy (TEM). This work shows a technique through which the nanocomposite powder is mixed with a resin, and after cured, thin sections can be obtained by ultramicrotomy. Another technique presented in this work deals with the observation of clay powder in solution. In this work High Resolution Electron Microscopy (HRTEM) was used to obtain images of the nanocomposites and clay. Images with a high level of details were showed. Through the use of such techniques, it was possible to observe two types of clay morphology in polymer matrix and its distribution. The dimensions and hexagonal layers of the natural clay used as nanofiller for the nanocomposite were also observed. The X-ray Diffraction (XRD) was used to investigate the kaolinite and nanocomposite.

Ultrastructural studies of Chondromyces crocatus vegetative cells

1975 ◽  
Vol 21 (11) ◽  
pp. 1815-1826 ◽  
Author(s):  
Thomas H. MacRae ◽  
Howard D. McCurdy
Keyword(s):  
Electron Microscopy ◽  
Cell Envelope ◽  
Thin Sections ◽  
Gram Negative ◽  
Ultrastructural Studies ◽  
Negative Cell ◽  
Slime Layer ◽  
Movement Characteristic ◽  
Gliding Movement

Electron microscopy of sectioned, chemically fixed Chondromyces crocatus revealed a microorganism with a typical gram-negative cell envelope. The cytoplasm contained, in addition to tubules and two types of granules, a membrane-associated structure (MAS) that, although less extensive, bears some resemblance to polar membranes observed in flagellated bacteria. Examination of swarming cells negatively stained in situ, as well as thin sections, established that cell division occurs by septum formation and that well-defined mesosomes are associated with the process. Polar pili and a compact, amorphous slime layer surrounding the cells were evident in shadowed preparations of in situ cells. The slime layer and pili, by providing cell-to-cell interconnections, may influence the organized gliding movement characteristic of C. crocatus and other myxobacteria.

The Progression from Optical Light Microscopy to Transmission Electron Microscopy in the Study of Soils

Clay Minerals ◽  
1994 ◽  
Vol 29 (2) ◽  
pp. 247-254 ◽  
Author(s):  
F. Van Oort ◽  
A. G. Jongmans ◽  
A. M. Jaunet
Keyword(s):  
Electron Microscopy ◽  
Clay Mineralogy ◽  
Tem Analysis ◽  
Undisturbed Soil ◽  
Thin Sections ◽  
Transmission Electron ◽  
Ultrathin Sections ◽  
Optical Light Microscopy ◽  
The Impact

AbstractThe use of electron microscopy to study clay microfabrics in thin-sections is discussed. A technique is described to isolate undisturbed microparts of pedofeatures from thin-sections, which are subsequently used for TEM analysis. Re-embedding with a polyester resin of undisturbed, in situ, neoformed clay microfabrics, obtained by microdrilling and preparation of ultrathin sections by microtoming with a diamond knife are emphasized; these steps enable micromorphology, clay mineralogy, microchemical and HRTEM analysis to be performed on one unique microsample of clay fabrics, with conserved micro-organization. Two examples on clay neoformation are presented to demonstrate that this technique can successfully be applied to unravel the impact of mineral alteration and clay neoformation in undisturbed soil samples on a micro- and a nanometer scale.

Combining SEM, EDS & EBSD: Challenges and considerations in the micro-analysis of rock thin sections

2020 ◽  
Author(s):  
Alexandra Stavropoulou ◽  
Matthew Hiscock ◽  
Balz Kamber ◽  
Juan-Diego Rodriguez-Blanco
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Sample Preparation ◽  
Data Acquisition ◽  
Modal Analysis ◽  
Thin Sections ◽  
X Ray ◽  
Material Characterisation ◽  
Scanning Electron

<p>Quantitative modal analysis of rock thin sections or liberation analysis of minerals processing plant materials can be very complex as grain sizes can vary by more than 7 orders of magnitude: Thin sections of rocks may contain extremely coarse grains (mm-sized crystals) down to glassy material with no long-range order (ordered domains <1 nm).</p><p>Material characterisation and modal analysis have traditionally been carried out with a combination of solid-state, microscopic and spectroscopic techniques (e.g., optical / scanning electron microscopy, powder X-ray diffraction, X-ray fluorescence spectroscopy). These techniques require different sample preparation routines, data acquisition and evaluation - a time-consuming process that may be considered too complex to implement in mineral processing plants despite requiring the relevant sample preparation equipment. Scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS provides an opportunity to carry out this characterisation in a more rigorous and, in certain cases, automated way. This process includes image thresholding (setting of grey levels of present phases by the analyst) and X-ray data collection with EDS. EDS is an ideal analytical technique for this work as it offers high acquisition speeds and the collection of the whole energy spectrum with a single detector, not requiring the selection of a fixed element list prior to data acquisition. Characterisation of coarse-grained rocks requires larger areas to be scanned in order to ensure representativity.</p><p>The analytical workflow can be further optimised by combining SEM-based analytical techniques for in situ, non-destructive, and potentially simultaneous bulk analysis. Electron backscatter diffraction (EBSD) is an SEM-based technique which can be used to determine the crystallographic properties and orientation of mineral grains, as well as to perform fabric analyses on polycrystalline materials. EBSD allows for crystallographic data to be collected simultaneously with chemical data and does not require powdered samples. As a result, the texture of the material can be fully preserved. The sample preparation requirements of the technique are similar to those for standard SEM-EDS, with an additional final polishing step, essential for the removal of surface imperfections, as the EBSD signal is generated on the sample surface. The coupling of EDS and EBSD datasets permits the enhanced interpretation of feature analysis data, allowing for a deeper understanding of the compositional, structural and textural properties of the sample. This, highly-efficient, in-situ, bulk material characterisation, is key for the mining industry, as it provides insights for optimising downstream procedures thereby saving time and resources and bolstering throughput and efficiency.</p>

scholarly journals Cytoskeletal network underlying the human erythrocyte membrane. Thin-section electron microscopy.

1980 ◽  
Vol 85 (3) ◽  
pp. 567-576 ◽  
Author(s):  
S Tsukita ◽  
S Tsukita ◽  
H Ishikawa
Keyword(s):  
Electron Microscopy ◽  
Human Erythrocyte ◽  
Erythrocyte Membranes ◽  
Human Erythrocyte Membrane ◽  
Thin Sections ◽  
Cytoskeletal Network ◽  
Thin Section Electron Microscopy ◽  
Human Erythrocyte Membranes ◽  
Section Electron

A filamentous network underlying the human erythrocyte membranes can be clearly visualized in situ by electron microscopy of thin sections of specimens fixed with tannic acid-glutaraldehyde. The network is composed of two layers: the first, a layer of vertical components with granular appearance, which are seen to be directly associated with the membrane proper, and the second, a horizontally disposed, anastomosing meshwork of filamentous components, approximately 9 nm in thickness, which are attached to the vertical components. The diameter and appearance of the filamentous components are similar to those of purified spectrin. EDTA treatment (0.1 mM, pH 8.0), which was used to extract spectrin and actin, resulted in the disappearance of the filamentous meshwork, leaving only the granular components.

scholarly journals Replication of kinetoplast DNA of Crithidia acanthocephali. I. Density shift experiments using deuterium oxide.

1976 ◽  
Vol 70 (2) ◽  
pp. 406-418 ◽  
Author(s):  
J E Manning ◽  
D R Wolstenholme
Keyword(s):  
Nuclear Dna ◽  
Deuterium Oxide ◽  
Gradient Centrifugation ◽  
Unit Length ◽  
Buoyant Density ◽  
Cesium Chloride ◽  
Kinetoplast Dna ◽  
Open Circular ◽  
Linear Molecules ◽  
Topological Interlocking

The protozoan Crithidia acanthocephali contains, within a modified region of a mitochondrion, a mass of DNA known as kinetoplast DNA (kDNA). This DNA consists mainly of an association of approximately 27,000 covalently closed 0.8-mum circular molecules which are apparently held together in a definite ordered manner by topological interlocking. After culturing of C. acanthocephali cells for 25 generations in medium containing 75% deuterium oxide, both nuclear DNA (rhonative, nondeuterated=1.717 g/cm3) and kDNA (rhonative, nondeuterated=1.702 g/cm3) increased in buoyant density by 0.012 g/cm3. The replication of the two DNAs was studied by cesium chloride buoyant density analysis of DNAs from exponentially growing cells taken at 1.0, 1.4, 2.0, 3.0, and 4.0 cell doublings after transfer of cells from D2O-containing medium into medium containing only normal water. The results obtained from analysis of both native and denatured nuclear DNAs indicate that this DNA replicates semiconservatively. From an analysis of intact associations of kDNA, it appears that this DNA doubles once per generation and that the newly synthesized DNA does not segregate from parental DNA. Fractions of covalently closed single circular molecules and of open circular and unit length linear molecules were obtained from associations of kDNA by sonication, sucrose sedimentation, and cesium chloride-ethidium bromide equilibrium gradient centrifugation. Buoyant density profiles obtained from these fractions indicate that: (a) doubling of the kDNA results from the replication of each circular molecule rather than from repeated replication of a small fraction of the circular molecules; (b) replication of kDNA is semiconservative rather than conservative, but there is recombination between the circles at an undefined time during the cell cycle.

Ultrastructural differences in the exosporium of the Sterne and Vollum strains of Bacillus anthracis

1968 ◽  
Vol 14 (12) ◽  
pp. 1297-1299 ◽  
Author(s):  
M. J. Kramer ◽  
Ivan L. Roth
Keyword(s):  
Electron Microscopy ◽  
Surface Layer ◽  
Bacillus Anthracis ◽  
Potassium Permanganate ◽  
Uranyl Acetate ◽  
Lead Citrate ◽  
Single Application ◽  
Thin Sections ◽  
Acetate Lead ◽  
Different Strains

Spores from three different strains of Bacillus anthracis were examined by electron microscopy for the presence of a hair-like nap previously reported to be present on the exosporium of spores of the Sterne strain (avirulent). In addition to that strain, the Vollum strain (virulent) and a rough, avimlent variant of the Vollum were utilized in the current studies.Spores were fixed with Kellenberger's standard OsO4 fixative and embedded in Maraglas. Thin sections were poststained with various combinations of the following: potassium permanganate, uranyl acetate, lead citrate. The nap on the exosporium of spores of the Sterne strain was revealed most clearly when thin sections were poststained with all of the aforementioned stains. Post-staining by a single application of any of the three reagents resulted in a nap that was barely perceptible.The surface of the exosporium of spores from the Vollum strain and the rough, avirulent variant was found to be quite different from that of the Sterne strain. On the two former, the surface layer is approximately one-third as thick as the layer of hairs in the nap on the latter.

Two- or three-way observations of the identical cell elements within the same sections by LM, TEM and/or SEM

1978 ◽  
Vol 36 (2) ◽  
pp. 82-83 ◽  
Author(s):  
Nakazo Watari ◽  
Yasuaki Hotta ◽  
Yoshio Mabuchi
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Fine Structure ◽  
Light Microscopy ◽  
Thin Sections ◽  
Transmission Electron ◽  
Identical Cell ◽  
Electron Microscopes ◽  
Scanning Electron

It is very useful if we can observe the identical cell elements within the same sections by light microscopy (LM), transmission electron microscopy (TEM) and/or scanning electron microscopy (SEM) sequentially, because, the cell fine structure can not be indicated by LM, while the color is; on the other hand, the cell fine structure can be very easily observed by EM, although its color properties may not. However, there is one problem in that LM requires thick sections of over 1 μm, while EM needs very thin sections of under 100 nm. Recently, we have developed a new method to observe the same cell elements within the same plastic sections using both light and transmission (conventional or high-voltage) electron microscopes.In this paper, we have developed two new observation methods for the identical cell elements within the same sections, both plastic-embedded and paraffin-embedded, using light microscopy, transmission electron microscopy and/or scanning electron microscopy (Fig. 1).

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