Electron microscopic visualization of capsular material of Pasteurella multocida types A and D labeled with polycationic ferritin.

The presence of capsular material on cells of Pasteurella multocida types A and D was determined by transmission electron microscopy after polycationic ferritin labeling. The capsule of agar-grown isolates of P. multocida type A was thick (70 to 90 nm) and regular, whereas that of type D isolates was thinner (20 to 30 nm) and irregular. Such layers were seen on cells from 4- to 6-h broth cultures, but cells from older cultures (12 to 18 h) had very little cell-associated capsular material. Our data indicate that the capsular material of P. multocida types A and D is morphologically different and that capsule production in broth culture is maximal during early log phase.     

Interaction between the VDAC channel and a polyanionic effector. An electron microscopic study.

The conductance of the voltage-dependent mitochondrial outer membrane channel is modulated by a synthetic anionic polymer. When added to suspensions of membrane crystals of the channel, the polyanion caused disordering of the usual parallelogram array and increased occurrence of a contracted form of the array. Correlation averages obtained from electron microscopic images of the channel crystals indicated a narrowing of the projected channel lumen in the presence of the polyanion and the appearance of new, narrow zones of stain exclusion on the outside of the channel. These effects are interpreted in terms of possible conformational changes induced in the channel by binding of the polyanion.     

Cytidine monophosphate as substrate for the electron microscopic visualization of alkaline phosphatase activity

Summary Since in histochemical reactions the liver alkaline phosphatase discloses only low activity with respect to beta-glycerophosphate, the authors have replaced the latter by cytidine monophosphate. With this substrate they obtained much better results: greater sensibility permitting to reduce the incubation time, and much more precise localization of the enzyme activity, at the ultrastructural level. Details of the method are given with a discussion of its specifity. The method was applied on liver tissue of normal albino rats and animals of the same strain with ligated common bile duct.This study was supported by a grant from the Fonds voor Wetenschappelijk Geneeskundig Onderzoek.     

Electron microscopic examination of capsular material from various serotypes of Actinobacillus pleuropneumoniae.

The capsular material on PPLO broth-grown cells of Actinobacillus pleuropneumoniae representing serotypes 1 to 10 was visualized by transmission electron microscopy after polycationic ferritin labeling and also after stabilization with specific antibodies. All the isolates examined were covered with a layer of capsular material whose thickness varied between 80 to 90 nm and 210 to 230 nm when examined by immunostabilization. We were also able to visualize A. pleuropneumoniae in lungs of infected pigs and to estimate the amount of capsular material covering the cells. Our results indicate that differences in capsular structure exist among the different A. pleuropneumoniae serotypes, and this result may explain in part why the serotypes are not equally virulent.     

A reliable method for preparation and electron microscopic visualization of nucleosomes in higher plants

An improved and reliable method is given for the preparation and electron microscopic visualization of nucleosomes in higher plants. The critical steps of the technique are indicated and enough details are given to allow for its use without any prior experience.     

Scanning electron microscopic visualization of collagen fibers in embryonic chick skin.

The disposition of collagen fibers in embryonic chick skin can be visualized by use of scanning microscopy (SEM). Chick back skin was removed from 8-day embryos, the epithelial and mesenchymal components were separated, and the mesenchyme was subjected to 10% trypsin treatment (Stuart, E. S., and Moscona, A. A. (1967) Science 157, 947–948), after which it was prepared for SEM by critical point drying and coating. Such preparations were largely free of cellular material. Cavities which presumably had contained the cells were present in a network of fibers. Skin of the scaleless mutant was also studied. In this mutant the collagen network was more irregular and collagen fiber diameter was more variable. These findings are discussed in connection with the formation of feather germ pattern.     

Light microscopic localization of cytochemical reactions in epoxy-embedded material for electron microscopy.

Tissues from mice were fixed in 1.5% glutaraldehyde, treated for the ultrastructural localization of alkaline phosphatase or Mg++-dependent adenosine triphosphatase, post-fixed in osmium tetroxide, dehydrated and embedded in plastic for electron microscopy. The sites of reaction were visualized in 1-mu plastic sections counterstained with toluidine blue, using a phase contrast microscope. The data show a close correlation between the sites of reaction observed with the phase contrast microscope and the sites studied with the electron microscope. The use of this technique for the study of these phosphatases in normal and pathologic tissues is recommended in order to achieve a high degree of accuracy in selecting a portion of the tissue sample for electron microscopy and to obtain greater resolution in the localization of these enzymes with the light microscope.     

Transmission and scanning electron microscopic study of the same cytologic material

The same cytologic material was successively examined by light microscopy (LM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). After the SEM examination, the specimens were rehydrated for a long period of time to allow the penetration of Epon 812 into the cells. The TEM examination showed the cell organelles to be comparatively well preserved. These consecutively performed LM-SEM-TEM examinations provided useful information on cytologic subjects, especially concerning the origin of the cells.     

Comparison of anode bacterial communities and performance in microbial fuel cells with different electron donors

Microbial fuel cells (MFCs) harness the electrochemical activity of certain microbes for the production of electricity from reduced compounds. Characterizations of MFC anode biofilms have collectively shown very diverse microbial communities, raising ecological questions about competition and community succession within these anode-reducing communities. Three sets of triplicate, two-chamber MFCs inoculated with anaerobic sludge and differing in energy sources (acetate, lactate, and glucose) were operated to explore these questions. Based on 16S rDNA-targeted denaturing gradient gel electrophoresis (DGGE), all anode communities contained sequences closely affiliated with Geobacter sulfurreducens (>99% similarity) and an uncultured bacterium clone in the Bacteroidetes class (99% similarity). Various other Geobacter-like sequences were also enriched in most of the anode biofilms. While the anode communities in replicate reactors for each substrate generally converged to a reproducible community, there were some variations in the relative distribution of these putative anode-reducing Geobacter-like strains. Firmicutes were found only in glucose-fed MFCs, presumably serving the roles of converting complex carbon into simple molecules and scavenging oxygen. The maximum current density in these systems was negatively correlated with internal resistance variations among replicate reactors and, likely, was only minimally affected by anode community differences in these two-chamber MFCs with high internal resistance.     

Conditions critical for optimal visualization of bacteriophage adsorbed to bacterial surfaces by scanning electron microscopy.

The potential of scanning electron microscopy as a tool for the detection of viruses on cell surfaces has been studied using bacteriophage P1 adsorbed to Shigella dysenteriae as a model system. Viral particles were readily detectable by scanning electron microscopy on the surface of infected cells which were fixed with glutaraldehyde followed by postfixation in OsO4 and prepared by critical point drying. The virus-studded surface of the infected cells differed markedly from the relatively smooth surfaces of uninfected control cells. Examination of the same preparations with transmission electron microscopy revealed numerous viral particles adsorbed to the surfaces of infected cells, whereas the control cells were free of viruses as expected. Glutaraldehyde fixation alone did not preserve the surface detail of infected cells: cells adsorbed with viruses were not distinguishable from control cells by scanning electron microscopy although by transmission electron microscopy viruses could be visualized. Air drying from water or absolute alcohol resulted in unsatisfactory preservation as compared to the appearance of infected cells prepared by the critical point method. Thus, scanning electron microscopy is capable of resolving viral particles on cell surfaces, but detection of these particles is completely dependent both on the method of fixation and on the technique of drying used.     

Scanning electron microscopic visualization of a microexudate prepared by the release of cells by urea

The scanning electron microscope (SEM) was used to examine the residue remaining after human fibroblasts, permitted to attach to plastic dishes in the absence of serum, were removed with buffered 1 M urea. The ‘urea carpet’ is entirely different from the “substrate-attached material” (SAM) of Culp [4, 5, 6] in that it contains no “footpad” material. Furthermore, the SEM pictures clearly indicate that urea carpet stimulates the adhesion and spreading of newly added fibroblasts.     

Comparison of the capsular response to the Biocell RTV and Mentor 1600 Siltex breast implant surface texturing: a scanning electron microscopic study.

The utility of mammary prosthesis texturing in the prevention of capsular contracture was established some 20 years ago. Various models of implant texturing are currently on the market. We decided to study two of the most popular implants with two different surface texturings: the Biocell RTV and the Mentor 1600 Siltex. An observation at the electron microscopic level of the implants' surfaces was achieved. At the time of a prospective survey on 10 patients, the capsule fragments corresponding to these two prostheses have been analyzed at the electron microscopic level. All prostheses were removed from the patients because of asymmetry or bad positioning. The aim of our study was to establish a correlation between these two frequent texturing surfaces and their corresponding capsules. Our results showed that only the Biocell's capsules present a mirror image with correspondence of the depressions on the prosthesis and contacts on the capsule. This phenomenon seems linked to the existence of a critical size of the pores constituting the implant surface. This observation leads us to the hypothesis of an adhesive effect between the prosthesis and its capsule. If this last is not directly linked to the prevention of capsular contracture, it can have an effect on implant stabilization in the primary mammary reconstruction and in the secondary corrections of asymmetry or bad position.     

Cell wall assembly in Bacillus subtilis: visualization of old and new wall material by electron microscopic examination of samples stained selectively for teichoic acid and teichuronic acid

Uranyl acetate staining of thin sections allowed a distinction to be made between cell wall material that contains teichoic acid and that which contains teichuronic acid. The stain was used to study the pattern of wall assembly in Bacillus subtilis undergoing transitions between growth conditions leading to incorporation of the different anionic polymers. The results showed that new material is incorporated along the inner surface of the cylindrical region of the wall confirming, by a more direct method, results obtained earlier with teichoic acid specific phages. New material appears to be evenly distributed along the inner surface and no evidence was obtained for the presence of specific zones of incorporation.     

Elastica-positive material in the atrial endocardium. Light and electron microscopic identification

The elastic layer of the endocardium is studied in various laboratory animals (mouse, rat, rabbit, cat, and dog) and in man. Coarse elastica-positive fibers form a tightly woven layer in the endocardium of the left atrium; the elastic layer consists of loosely arranged delicate fibers in the endocardium of the right atrium. Electron microscopy shows the elastic material to consist of homogeneous elastin (E) and of elastic fiber microfibrils (EFM). Elastic material in the endocardium of the left atrium is mainly formed of E with few EFM present. By contrast, the portion of EFM predominated that of E in elastic fibers from the right atrium, where some elastica-positive fibers even appear as pure bundles of microfibrils. This was also observed in human material obtained from aged individuals (8th decennium). It is concluded that EFM are not only progenitors of E but represent an independent fibrous component of the connective tissue.     

Comparison of different kinds of probes used for analysis of variant telomeric sequences

In this work we aimed to compare and critically evaluate results obtained by different types of probes used for hybridisation to detect variant telomeric sequences with respect to their reliability and information value. Using slot-blot hybridisation we investigated three types of probes (oligonucleotides, cloned fragments and concatenated probes) under various conditions of hybridisation and washing. The concatenated probes exhibited the highest specificity although all three types are suitable for hybridisation of telomeric sequences under appropriate experimental conditions. We demonstrate how understanding generated from these data enables interpretation of hybridisation patterns of oligonucleotide probes to genomic DNAs.