bluuebunny/crossref_metadata_2025 huggingface dataset:
Accuracy of linear polymer crystal structures determined from electron diffraction intensities: Problems with zonal data
Authors: Dorset Douglas L.
Published: June 2020

In contrast to analyses based on X-ray and neutron diffraction intensity data, electron crystal structure determination for organic materials is only a crudely-developed procedure. Although the pioneering work of Vainshtein and co-workers has been very important for realization of the technique's advantages, self-consistent procedures based on earlier-derived diffraction theory have only recently emerged, enabling a reasonable estimate of what structural information might be obtained from a given microcrystalline organic specimen and how this might be best achieved. Problems which are unresolved include the optimal refinement procedure for an unknown structure and also the adequate identification of the correct crystal structure during this refinement process.

The behavior of the crystallographic residual(R) during structure refinement is manifested by various minima in a multidimensional parameter space. The description of this space is more complicated for electron diffraction than for X-ray diffraction, although both cases include atomic position, atomic thermal vibration, atomic occupancy, “extinction”, and crystal distortion.
Microstructure investigation of initial formation of the Pd2Si-Si interface by TEM and ion channeling techniques
Authors: Yokota Y. , Wittimer M. , Ho P.S.
Published: June 2020

Recent synchrotron-radiation experiment have established that the formation of the Schottky barrier at some transition metal-Si interface is essentially completed upon metal deposition of the first few monolayers. One problem of basic importance is the structural morphology and metal atom distribution of the initial silicide-Si interface. To complement our studies on the electronic and electrical characteristics, transmission electron microscopy (TEM), reflection electron microscopy (REM) and ion channeling techniques were used to investigate the microstructure of the initial Pd2Si-Si interface.

Samples were prepared in UHV chember by e-beam evaporation of about 30-80 Å Pd on Si (100) or (111) substrates at room temperature then annealed at 200°C in various times to form Pd2Si. Back-etching of the Si substrates was finished with CP-4 solution. Samples were examined using a JEOL 200 CX microscope with TEM and REM mode.

Fig. 1 is a high resolution lattice image of Pd2Si on (111) Si and a diffraction pattern. The amount of Pd deposited was estimated to be 80Å by ion back scattering
TEM studies of dark line defects in Fa1-xAlxAs heterostructures
Authors: Liliental Zuzanna
Published: June 2020

Light-emitting diodes (LED's) are used as sources in fiber optical communication systems. They are required to exhibit high quantum efficiency and high reliability. But, in such devices, a degradation mechanism can take place. Non-radiative recombination occurs and dark line defects (DLD's) grow through the active layer and its surroundings. Such defects, observed in luminescence topographs have been reorganized from TEM observations as dislocation networks.

Our recent investigations of the Ga1-xAlx As structure have shown that the defects (loops, dipoles, helical Dislocations) were not only present in the active layer, but a high density of them were observed in the window layer as well. These were mainly helical dislocations and loops which were created around precipitates. The window layer was doped with tellurium at concentrations of about (1-4)×1018/cm3. It is probable that at this concentration excess tellurium (or its compounds) were precipitated.
Wide area beam averaged AEM of precipitate particles extracted on replicas from type 316 stainless steel
Authors: Maziasz P. J. , Odette G. R.
Published: June 2020

Extraction replicas are an important complement to in-foil analysis for accurate phase identification and composition measurements in studying precipitation in complex alloys such as type 316 stainless steel. Analysis of small particles without matrix interference is particularly easy on replicas. Background or in-hole counts on clean replicas are very low compared to in-foil. This is important for reactor-irradiated materials where intrinsic radioactivity emission interferes with or obscures x-ray detection in-foil. This work introduces another advantage of replicas by demonstrating an analysis in which a wide area beam is used to blend spectra from many particles into a composite averaged spectrum. Such an averaged spectrum better represents the elemental redistribution from the original matrix to the precipitate microstructure and can yield relative phase fractions upon deconvolution if the individual phase compositions are known.
Characterization of precipitate morphology and composition in a Nb/V microalloyed steel
Authors: Newkirk J. W. , Hansen S. S.
Published: June 2020

It is now well known that small additions of Nb, Ti or V can have a significant effect on the structure and properties of low-carbon steels. Appropriate control of composition and processing produces a refined ferrite grain size and a fine precipitate dispersion, the result being an outstanding combination of strength and toughness. These structural changes are both strongly influenced by the dissolution and re-precipitation of alloy carbonitrides during processing. Therefore, characterization of the precipitate morphology/composition in the final product is important in optimizing the design and processing of microalloyed steels.

In this investigation, a control-rolled microalloyed steel was evaluated with a modern analytical electron microscope. Material was taken from 0.75-inch-thick plates with a nominal composition of 0.15C, 1.50Mn, 0.04Nb, 0.08V, 0.003Ti, 0.04A1 and 0.010N. Samples were prepared for extraction replicas by standard metallographic techniques, etched in 2% nital for about 30 seconds and then stripped with cellulose acetate. After backing with carbon, the replicas were placed on copper grids and the cellulose acetate dissolved.
Transverse microstructure of oxide formed on 20/25/Nb stainless steel
Authors: Bennett M.J. , Desport J.A. , Labun Patricia A.
Published: June 2020

In the United Kingdom commercial advanced gas cooled nuclear power plants the fuel cladding is a 20% Cr/25% Ni/niobium stabilised (20/25/Nb) austenitic stainless steel and the coolant is carbon dioxide based. The oxidation behaviour of this steel has been studied extensively, e.g., with the main emphasis being directed to the oxidation kinetics and scale composition, as revealed by conventional surface analytical and X-ray diffraction techniques. This paper reports the first transmission electron microscopy undertaken on transverse sections through an oxide scale formed on this steel.

The 20/25/Nb steel specimen was a coupon of rolled sheet, which had the composition given in Table. The surface of the steel was abraded on 600 grit SiC paper and subsequently was hydrogen annealed for 30 mins, at 930°C. Oxidation in carbon dioxide was continued for 4900h at 825°C (a probable maximum fuel cladding operating temperature). The magnitudes and kinetics of both oxidation and concurrent spallation have been reported. For the preparation of a TEM foil the oxide scale was protected and the oxide/gas interface was defined by a stainless steel coating deposited by sputter ion plating (SIP).
Application of convergent-beam electron diffraction to the detection of lattice parameter changes in hexagonal close-packed metals
Authors: Kohler V. L. , Shelton C. G. , Ralph Brian
Published: June 2020

Convergent beam electron diffraction (CBED) patterns have been used in several different applications to materials problems (summarised by Steeds) and has more recently been used to quantify shifts in the lattice parameters of cubic materials (e.g. 2). This technique has proved highly sensitive to such changes, capable, via the use of very simple geometrical computer simulations, of the detection and quantification of changes in lattice parameters of hexagonal alloys.

Alloy systems based on zinc and titanium were used. A simple geometrical computer simulation was used to quantify the shifts, ignoring dispersion surface effects, in the higher order Laue zone (HOLZ) lines upon change in the lattice parameters. X-ray diffraction data from each of the alloys was obtained to provide a standard for comparison. The sensitivity of each zone axis pattern to changes in either a or c was determined from the magnitude of the HOLZ line shifts in the CBED pattern.
Scattering-angle dependence of signal/background ratio of inner-shell electron excitation loss in EELS
Authors: Oikawa T. , Inoue M. , Honda T. , Kokubo Y.
Published: June 2020

EELS allows us to make analysis of light elements such as hydrogen to heavy elements of microareas on the specimen. In energy loss spectra, however, elemental signals ride on a high background; therefore, the signal/background (S/B) ratio is very low in EELS. A technique which collects the center beam axial-symmetrically in the scattering angle is generally used to obtain high total intensity. However, the technique collects high background intensity together with elemental signals; therefore, the technique does not improve the S/B ratio. This report presents the experimental results of the S/B ratio measured as a function of the scattering angle and shows the possibility of the S/B ratio being improved in the high scattering angle range.

Energy loss spectra have been measured using a JEM-200CX TEM with an energy analyzer ASEA3 at 200 kV.

Fig.l shows a typical K-shell electron excitation edge riding on background in an energy loss spectrum.
The low-resolution 3D-structure of porin, a channel-forming protein in E. coliouter membranes
Authors: Engel A. , Dorset D.L. , Massalski A. , Rosenbusch J.P.
Published: June 2020

Porins represent a group of channel forming proteins that facilitate diffusion of small solutes across the outer membrane of Gram-negative bacteria, while excluding large molecules (>650 Da). Planar membranes reconstituted from purified matrix porin (OmpF protein) trimers and phospholipids have allowed quantitative functional studies of the voltage-dependent channels and revealed concerted activation of triplets. Under the same reconstitution conditions but using high protein concentrations porin aggregated to 2D lattices suitable for electron microscopy and image processing. Depending on the lipid-to- protein ratio three different crystal packing arrangements were observed: a large (a = 93 Å) and a small (a = 79 Å) hexagonal and a rectangular (a = 79 Å b = 139 Å) form with p3 symmetry for the hexagonal arrays. In all crystal forms distinct stain filled triplet indentations could be seen and were found to be morphologically identical within a resolution of (22 Å). It is tempting to correlate stain triplets with triple channels, but the proof of this hypothesis requires an analysis of the structure in 3 dimensions.
Side bridge geometry after quick-freezing of stimulated and unstimulated frog skeletal muscle fibers
Authors: Sommer J.R. , Nassar R. , Walker S.
Published: June 2020

Quick-freezing allows the structural analysis of timed perturbations of morphology. We are presenting preliminary results concerning the feasibility of studying directly the side bridge geometry of actin-myosin interactions within the time course of a twitch in single intact frog skeletal muscle fibers, both by freeze-substitution and freeze-fracture after quick-freezing, and following various time intervals between stimulation and impact of the fibers on a liquid He-cooled copper block.

Materials and Methods. The quick-freezing device was a "Slammer"(Polaron) for which the electronics had been redesigned; they are capable, in combination with a Grass S48 stimulator, of any stimulation interval between 0 and 1 sec prior to freezing, including tetanus. The actual elapsed time between stimulation and freezing is recorded with a digital clock. Single intact tendonto- tendon frog skeletal muscle fibers (semitendinosus of r. temporaria) or toe muscle bundles (r.pipiens) were isolated by sharp dissection and placed between coextensive Pt stimulation wires on blackened 2% agarose, the height of which on the specimen holder was adjusted appropriately with respect to a spacer ring both, to calibrate the impact time and to prevent smashing of the fibers.
The morphology of the collecting system orifices in the normal human kidney
Authors: Gaines Joseph J.
Published: June 2020

The renal collecting ducts empty via the ducts of Bellini into the area cribrosa of the renal papillae. The morphology of the orifices of the collecting duct emptying into the area cribrosa is of interest because of the relationship to intrarenal reflux and pylonephritic scarring. The purpose of this paper is to anatomically characterize these ductal orifices using scanning electron microscopy in the normal adult human kidney and to discuss possible pathological implications.

Renal papillae were obtained from autopsy material of five normal adult human kidneys that were initially fixed in 10% buffered formalin. Three papillae were randomly selected from each kidney for a total of 15 papillae. The specimens were washed in distilled water, 0.5N hydrochloric acid, and again in distilled water. Surface debris were gently removed with a fine camel hair brush as needed. The samples were postfixed in osmium tetroxide, washed in distilled water, dehydrated in a graded series of ethanols, mounted on aluminum stubs, and sputter coated with gold-palladium. The specimens were examined in a JE0L JSM-35 scanning microscope at 25KV.
Cortical localization of a stage-specific surface glycoprotein and its polarization during early mouse development
Authors: Polak-Charcon S. , Johnson L. , Calarco-Gillam P.
Published: June 2020

Stage-specific surface antigens synthesized and expressed during mouse preimplantation development have been detected by a rabbit antiserum prepared against mouse blastocysts (A-BL2). Serological and biochemical work showed the antigens (BL) were a glycoprotein doublet of 65-70,000 daltons expressed on the cell surface at the 4-cell stage, reaching a maximum on the 8-16 cell stage, and declining on the blastocyst. Synthesis and expression of BL occur although little classical RER or Golgi material are detectable. The present study utilized immunoelectron microscopy (IEM) and the peroxidase-antiperoxidase technique to determine the intracellular distribution of BL antigens and, potentially, their site of synthesis, and to follow BL antigen expression on the plasma membrane during early mouse development.

Mouse embryos from unfertilized eggs to blastocysts were obtained as described. Some embryos were treated with pronase to remove the zona pellucida. Embryos were fixed 10 min in 0.05% gluteraldehyde in phosphate buffer (PB). Some embryos were permeabilized with saponin buffer for 30 min; some were not. All were incubated with either A-BL2 IgG or normal rabbit serum IgG (NRS), washed and incubated with HRP-conjugated goat anti-rabbit IgG.
Studies on the interaction of the complement system with Schistosoma mansoni
Authors: Rasmussen Kathleen
Published: June 2020

The mechanisms by which adult schistosomes escape the host's immune response are a matter of considerable speculation. Much of the research in this area has dealt with host or host-like antigens associated with the tegument of the parasite and their possible role in protecting the parasite from immune attack. The presence of receptors for the third component of complement (C3) on the dorsal surface of the adult male schistosome has been demonstrated, although the presence of complement components themselves has not been definitively shown. The purpose of this study was to determine if C3 is present on the adult male schistosome. Parasites collected from mice with 8 week infections were incubated in peroxidase-conjugated goat anti-mouse C3 and further processed for transmission electron microscope examination. The peroxidase reaction product was localized in the surface pits (Figure 1), but not on the free surface. Binding of this antisera was completely blocked by preincubation of the parasites in unconjugated goat anti-mouse C3 (Figure 2), but not by normal goat IgG.
Ultrastructural studies of the virions and paracrystalline inclusions in the skin tumor of molluscum contagiosum
Authors: Sun C.N. , Bowen W.R. , Watson J.H.L.
Published: June 2020

Molluscum contagiosum is a benign tumor of human skin. Using light microscopy and TEM, early investigators demonstrated the presence of virions in the inclusion cells of these tumors. Recently a biopsy of a skin lesion with molluscum contagiosum on the forehead of an 84-year old patient was obtained. The present study, using epoxy embedments for TEM and critical point dried virus particles for SEM, clarifies some of the earlier observations and reports the presence of previously undescribed paracrystalline inclusions in the cytoplasm.

The skin lesion consists of a localized and stratified proliferation of inclusion cells. Our studies were confined to the keratinous stratum. Numerous mature virions each approximately 250 nm in length and 150 nm in diameter, were present within the inclusion cells (Fig. 1,4). With SEM, each virion was found to be more oval-shaped than previously reported. Each virion had an electron-dense nucleoid core surrounded by an amorphous lateral body and an envelope.
Structural features of lymphocyte-stimulated mucopolysaccharide coats in human glioma-derived cells
Authors: Greenwood M.A. , Smith B.H. , Gately M.K. , Muul L. , McKeever P.E.
Published: June 2020

As part of a series of studies of the properties of human glioma cells that contribute to their ability to escape cell-mediated immune attack (Gately et al.,(1982)we have examined the ultrastructural features of a protective mucopolysaccharide coat secreted by some of these brain tumor cell lines. This ruthenium red-positive coat or "halo" is formed or greatly increases in size in response to the presence of lymphocytes or a soluble factor released therefrom. It blocks the approach of cytotoxic lymphocytes to the tumor cells and hence tumor cell killing. Hyaluronidase appears to be a major structural component. The "halo" is destroyed by bovine testicular or streptomyces hyaluronidase, and chondritinase ABC.

To determine the ultrastructural features of this halo we have examined 5 human glioma cell lines in vitro. These were derived from I Grade II and 4 Grade IV astrocytomas, specimens of which were removed at surgery. Glioma derived (1000 per Costar well) were plated along with the soluble coatstimulating lymphocyte factor. At 24 hours erythrocytes were added as coat indicator at 24 hours.
Quantitative EM of gap junction distribution in mutant drosophila wing discs
Authors: Ryerse J.S.
Published: June 2020

Gap junctions are intercellular junctions found in both vertebrates and invertebrates through which ions and small molecules can pass. Their distribution in tissues could be of critical importance for ionic coupling or metabolic cooperation between cells or for regulating the intracellular movement of growth control and pattern formation factors. Studies of the distribution of gap junctions in mutants which develop abnormally may shed light upon their role in normal development. I report here the distribution of gap junctions in the wing pouch of 3 Drosophila wing disc mutants, vg (vestigial) a cell death mutant, 1(2)gd (lethal giant disc) a pattern abnormality mutant and 1(2)gl (lethal giant larva) a neoplastic mutant and compare these with wildtype wing discs.

The wing pouch (the anlagen of the adult wing blade) of a wild-type wing disc is shown in Fig. 1 and consists of columnar cells (Fig. 5) joined by gap junctions (Fig. 6). 14000x EMs of conventionally processed, UA en bloc stained, longitudinally sectioned wing pouches were enlarged to 45000x with a projector and tracings were made on which the lateral plasma membrane (LPM) and gap junctions were marked.
Radiation Damage in Amorphous Nb40Ni60
Authors: Rechtin M. D. , Vander Sande J. , Baldo P. M.
Published: June 2020

We have performed a study of displacement radiation damage in a relatively new type of material, the noncrystalline refractory-transition metal Nb40Ni60. This alloy has a crystallization temperature of ˜1000 K, and therefore exhibits excellent thermal stability; it also has a high microhardness and shows good ductility. This material was prepared by a splat-quenching method and properties of this alloy are discussed in detail in Ref. 1.

We have simulated the effects of fast-neutron displacement-induced damage by a 3.5-MeV Ni+ beam that has a displacement per atom rate of ˜3 x 10-3 dpa/s. As shown in Fig. 1, the Ni+ ions have a range of ˜0.8 μm and a peak in induced damage at 0.65 μm as calculated by the Brice Code.2 This result is based on a weighted average of the elemental crystalline densities, and variations in packing density of about ±15% alter the location of peak damage only ±0.1 μm.
Anticontamination Device for STEM
Authors: Hren J. J. , Jenkins E. J. , Aigeltinger E.
Published: June 2020

Contamination buildup during stationary microbeam EDS analysis or during microdiffraction has now been widely recognized to be a severely limiting artifact of STEM systems. Recent work suggests that both the system and the specimen contribute to the severity of contamination (1,2). Ultra-high vacuum near the specimen does not completely cure the problem, but it is very helpful in some cases. The newer STEM instruments with vacuums in the range 107 torr in the specimen area also seem to require a substantially longer time for buildup, particularly when ion pumping in the condensor/gun system is employed and the use of O-rings is minimized. However, one would hope there are working solutions short of exchanging the entire vacuum system or buying a new microscope. We therefore turned to more practical means for suitably altering the microscope to help minimize contamination.
Diffraction and Microscopy Studies of the Structure of Grain Boundaries
Authors: Guan D. Y. , Gaudig W. , Sass S. L.
Published: June 2020

It is now well established that the grain boundary between two crystals consists of a thin region at the interface which is at least several atom distances thick. As is well known, the structure and properties of this relatively thin slab of material is of considerable scientific and technological interest. This paper is concerned with the study of the structure of grain boundaries. A good starting point for this work, therefore, is to ask what are the important questions that need to be answered about the structure of the grain boundary region. These questions are: 1) Is the boundary struc ture periodic? If so, what is the unit cell symmetry and dimensions? 2) What patterns of atomic relaxation exist in the boundary? Can these relaxation patterns be described in terms of primary or secondary grain boundary dislocations? 3) What is the detailed atomic structure of the grain boundary?
Fine Structure of Interfaces as Revealed by Lattice Fringe Imaging
Authors: Sinclair R.
Published: June 2020

Interfaces play a critical role in determining the ultimate macroscopic properties of many materials. Their presence of course can be detected by conventional microscopy methods. However, many of the phenomena associated with interfaces still lack a basic understanding in terms of fine structure and this is clearly an area to which high resolution TEM techniques can be applied. Definite progress has been achieved recently and this paper reviews the contributions made by lattice fringe imaging.

It is well-known that the experimental conditions for obtaining lattice images are quite stringent. This is even more the case if two or more crystal orientations or phases are involved. For instance a grain boundary separates two crystals whose orientations are in general random with respect to the electron beam.
Misfit Dislocations
Authors: Matthews J. W.
Published: June 2020

In 1949 Frank and van der Merwe (1) considered the accommodation of misfit between one crystal and another using a simple model. The model consisted of a linear chain of atoms that was placed on a substrate in which there were sinusoidal corrugations. They showed that - in systems where the bonding between the atoms in the chain was comparable to the bonding of the atoms to their substrate - it was energetically favorable for a misfit of ≲ 7% to be accommodated by strain. An experimental system which resembles the one considered by Frank and van der Merwe, and is particularly well suited to test their predictions, is the bubble model of Bragg and Nye (2). Figure 1(a) shows a row of soap bubbles that is separated from a raft of bubbles by a barrier. The misfit between the row and raft is ∽7% . Figure 1(b) shows the bubbles after removal of the barrier. It can be seen that all the misfit is accommodated by strain.
An Improved Quantitative Image Analyser
Authors: Fallon J.P. , Gregory P.J. , Taylor C.J.
Published: June 2020

Quantitative image analysis systems have been used for several years in research and quality control applications in various fields including metallurgy and medicine. The technique has been applied as an extension of subjective microscopy to problems requiring quantitative results and which are amenable to automatic methods of interpretation.

Feature extraction. In the most general sense, a feature can be defined as a portion of the image which differs in some consistent way from the background. A feature may be characterized by the density difference between itself and the background, by an edge gradient, or by the spatial frequency content (texture) within its boundaries. The task of feature extraction includes recognition of features and encoding of the associated information for quantitative analysis.

Quantitative Analysis. Quantitative analysis is the determination of one or more physical measurements of each feature. These measurements may be straightforward ones such as area, length, or perimeter, or more complex stereological measurements such as convex perimeter or Feret's diameter.
The Application of Electron Energy Loss Spectroscopy in Glass - Ceramic Microstructural Analysis
Authors: Anderson R. M. , Kumar A.
Published: June 2020

The identification of unknown phases in crystallized glasses or ceramics has been difficult because the phases are generally composed of many elements; they crystallize into low-symmetry lattices; they contain numerous impurities, which may alter crystal structure or allow the observation of metastable phases; and they are not well represented in standard compilations of crystal data. Compounding the problem is the fact that energy- dispersive x-ray analysis (EDX) for elemental content can not be employed for elements with Z<11. This eliminates any possibility of qualitative analysis of the important Li, Be, and B glasses as well as determination of O, C and N content. Electron Energy Loss Spectrometry (ELS) has been shown to be a powerful method for the analysis of light elements. The ELS method is far more efficient at detecting light elements than x-ray detection, because the yield of energy loss electrons to inner shell excitation and ionizations is unity and because the electrons, which have lost energy encountering the sample, are scattered through very small angles, with the result that collection efficiencies are high.
On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder
Authors: Walsh J. M. , Gumz K. P. , Whittles J. C. , Kear B. H.
Published: June 2020

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.

The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.
Identification of Zirconium Hydride Phases in the Electron Microscope
Authors: Cann C.D. , Sexton E.E.
Published: June 2020

The presence of zirconium hydride precipitates may have important effects on the mechanical behaviour of zirconium alloys. This has recently been demonstrated in the case of hydrogen induced, delayed cracking of pressure tubes in a CANDU-PHW* reactor (1). Electron microscope studies have been initiated to determine the exact role that hydrides play in the cracking process. One aspect of interest is the particular phase of hydride present. For the range of hydrogen concentrations involved, 10 to 500 μg/g, both the fct γ-hydride and fee δ-hydride phases occur. In the past accurate measurements of spot spacings and interplanar angles in electron diffraction patterns or precise X-ray measurements have been required to differentiate between these phases due to the similarity of the fee and fct lattice parameters (2). We wish to report here, however, a much quicker method for identifying the γ-phase directly from its diffraction pattern in the electron microscope.
Ultrastructural Studies on Genital Infection with the Chlamydial Agent of Guinea Pig Inclusion Conjunctivitis
Authors: Soloff B. L. , Barron A. L. , White H. J. , Rank R. G.
Published: June 2020

Chlamydial organisms (specifically C. trachomatis) have been implicated as a frequent cause of genital infection in the human (1). Study of the histo- pathological aspects of such infections has been impeded because of difficulties in obtaining adequate tissue specimens and the lack of a suitable experimental host. In 1964, Murray (2) isolated the causative agent of guinea pig inclusion conjunctivitis which possesses similarities to human inclusion conjunctivitis. This guinea pig organism was found to be a member of the Chlamydia psittaci subgroup and was designated as the Gp-ic agent. Male guinea pigs have been successfully infected with Gp-ic by intraurethral inoculation. Transmission of the infection to the female by sexual contact has been demonstrated (3). We are not aware of any ultrastructural studies to date concerning the development of this agent in genital tissue.

Studies in our laboratory have established that, in our guinea pig model, the cervix is the major site of injection.
Annulate Lamellae in Human Tumor Cells
Authors: Sun C. N. , White H. J.
Published: June 2020

Annulate lamellae seem to have a widespread occurrence in animal tumor cells; however, presence in human neoplastic material has been reported in only a few cases (1,2). Recently, we found these structures from biopsies of cerebellar metastatic carcinoma, testicular seminoma, retinoblastoma and in three melanomas.

These annulate lamellae are arranged in stacked parallel arrays in the cytoplasm of tumor cells. In some cases, annulate lamellae have been found in contact with the nuclear envelope. The number of annulate lamellae observed to comprise a single stack varies from 5-18 in the cerebellar tumors (Fig. 1), 2-4 in the seminoma (Fig. 2), 2-8 in the retinoblastoma and 8-10 in the melanomas (Fig. 3). All the lamellae structures are connected with the rough endoplasmic reticulum. By appropriate section, "pores" on the membranes are seen which have an outside diameter of approximately 1000 - 1600 A.
Endogenous Peroxidase Localization in Kupffer Cells of the Fetal Rat Liver
Authors: Pino Richard M.
Published: June 2020

This study confirms the presence of endogenous peroxidase in fetal Kupffer cells. In adult hepatic sinusoids Kupffer cells are peroxidase positive; endothelial cells are not.1 The fetal rat liver sinusoidal endothelium during development changes from a lining similar to that found in adult bone marrow to an adult liver type.2 Cells that resemble adult Kupffer cells are evident at 13 days gestation and can endocytize carbon beginning at 14 days.

Sixteen day Wistar rat fetuses were exposed in utero after ether anesthesia of their mothers. Colloidal carbon (Pelikan, Gunther Wagner) diluted 1:1 with double strength Tyrode1s solution, or as a control, single strength Tyrode's solution without carbon, was injected (0.01-0,03ml) into the fetal umbilical veins with a 30 gauge needle.2 After allowing one minute for the injected material to circulate, the fetuses were decapitated and the livers were removed and diced into small pieces.
Tannic Acid as Fixative and Stain for Amyloid Tissues
Authors: Rodgers O. G. , Shirahama T. , Cohen A. S.
Published: June 2020

Amyloid is a protein deposited in a variety of organs in the disorder amyloidosis which is widely distributed in the animal kingdom. The identification of this substance and diagnosis of the disease is largely dependent on its morphologic characteristics and tinctorial properties by light microscopy and the fibrillar structure by electron microscopy (1). In electron micrographs prepared conventionally, very often the amyloid fibrils show low electron density, making it difficult to identify small airyloid deposits when scanning by low magnification, and difficult to analyze ultrastructural details at high magnification. After testing various fixatives and stains to achieve good fixation and staining of the anyloid fibrils, we have found that the use of tannic acid as a fixative (2) may satisfy these objectives.

Various tissues (skin, tongue, prostate, spleen, liver and kidney) were obtained at biopsy, surgery or autopsy from patients with primary, secondary, myelcma-associated or hereditary amyloidosis. Spleen, liver and kidney from CBA/J mice in which amyloidosis was induced by daily casein injections were also used.
Freeze Fracture Studies of Particle Segregation in Compacted Myelin
Authors: Benitez C. , Caspar D.L.D. , Kirschner D.A.
Published: June 2020

The membrane faces of the myelin of fresh-frozen sciatic nerve exhibit small uniformly distributed particles1. We have found that particle aggregation over large areas of the membrane faces, showing extensive intermembrane correspondence, can be induced by treatment with dimethylsulfoxide, polyethylene glycol, acetone, sodium chloride, calcium chloride, and by dehydration at high or low relative humidity. A similar but transient aggregation is induced by brief exposure to glycerin. Observations on optic nerve and brain white matter indicate that central nervous system myelin is affected in a manner similar to peripheral nervous system myelin.

With these treatments the myelin generally was not grossly disrupted and the lamellae were well ordered. Two distinct membrane populations were clearly seen (Fig. 1). The particle-rich membrane population had a rough appearance in cross fracture and a period of about 180Å. The smoother, relatively particle-free membrane had a period of about 125-135Å.
Serial Section Analysis of Acrosomal Complex in Late Phases of Spermiogenesis of Acrida Lata Motschulsky (Orthoptera)
Authors: Yasuzumi G. , Matano Y. , Sakai T. , Shimakura S.
Published: June 2020

Although considerable attention has been paid to the formation of acrosomal complex and its mature form in several families of Orthoptera (1, 2, 3, 5, 6), the relationship between the acrosomal membrane (5) and the acrosome proper remains as yet unsettled. To gain an insight into several problems of induction for sper- miogenesis, electron microscopy of serial sections is required. Serial sections of 30-60 nm thick are of value in establishing the reality of presumable membrane continuities.

The testis of the grasshopper, Aovida lata Motschulsky, was fixed with a triple fixation procedure (4). The fixed specimens were embedded in epoxy Epon resin by a routine method for electron microscopy. The tissue was sectioned with diamond knives on an LKB ultrotome. The serial sections in this study were at flat gray reflection color (30-60 nm in thickness). Serial sections were placed on 100-mesh copper grids. They were stained doubly with uranyl acetate followed by lead citrate.
Fine Structure of Laser Induced Lesions of Rhesus Monkey Retina
Authors: Blystone Robert V. , Bowie William H.
Published: June 2020

The retinas of a rhesus monkey were exposed to mode-locked visible laser pulses operated under the following exposure conditions: pulse train duration, lOmsecj pulse width, ∽250 psec; pulse repetition rate,∽104 mHz; wavelength, 514.5 nm. Two threshold levels were determined on the basis of ophthalmoscopically observed lesions at one hour post treatment and at 24 hours post treatment. One hour lesion threshold was∽430 mW peak pulse power and 24 hour lesion threshold was ∽210 mW peak pulse power. A grid of 16 exposures ranging from 282 to 1587 mW were placed in the macula region of the retina with adjacent marker lesions used for co-ordinate calibration. After six months post treatment, the animal was sacrificed and perfused with 3% glutaraldehyde in 0.1 M sodium cacodylate buffer. The eyes were post fixed in buffered 1% osmium tetroxide, dehydrated and embedded in Spurr plastic.
Scanning Electron Microscopy of the Male Nematode Physaloptera (Tetradelphynema)
Authors: Behbehani Bahja I. , Nayak Ramesh K. , McCoy Randall E.
Published: June 2020

Nematodes are elongate, unsegmented worms with an elastic cuticle made of protein. Few published references concerning scanning electron microscopy of nematode are available and there is paucity of information at the ultrastructural level on cuticle forming male reproductive structures. The species of the genus Physaloptera (tetradelphynema) commonly live as parasites in the adult form in the stomach of the desert rodent Gerbillus cheesmani. To date, the three-dimensional surface features of this spiruroid nematode have not been described. The main purpose of this investigation was to elucidate the surface features of the male nematode utilizing the current techniques of scanning electron microscopy.

Adult worms were collected in the laboratory from the stomach of the gerbil, Gerbillus cheesmani. They were washed in PO4 buffer solution and subsequently fixed overnight in 2.5% glutaraldehyde in 0.1 M cacodylate buffer. Following fixation, the specimens were washed 3 times in buffer and sonically cleaned for 30 seconds to remove debris adhering on the body wall of the nematode.
Microdensitometer—computer correlation analysis of ultrastructural periodicity
Authors: Ensor D.R. , Jensen C.G. , Fillery J.A. , Baker R.J.K.
Published: June 2020

Because periodicity is a major indicator of structural organisation numerous methods have been devised to demonstrate periodicity masked by background “noise” in the electron microscope image (e.g. photographic image reinforcement, Markham et al, 1964; optical diffraction techniques, Horne, 1977; McIntosh,1974). Computer correlation analysis of a densitometer tracing provides another means of minimising "noise". The correlation process uncovers periodic information by cancelling random elements. The technique is easily executed, the results are readily interpreted and the computer removes tedium, lends accuracy and assists in impartiality.

A scanning densitometer was adapted to allow computer control of the scan and to give direct computer storage of the data. A photographic transparency of the image to be scanned is mounted on a stage coupled directly to an accurate screw thread driven by a stepping motor. The stage is moved so that the fixed beam of the densitometer (which is directed normal to the transparency) traces a straight line along the structure of interest in the image.
Multivariate analysis of phenyl mercuric acetate effects on aureobasidium pullulans ultrastructure
Authors: Crang R.E. , Loesch A.J. , Pechak D.G.
Published: June 2020

The effects of the inhibitory agent phenyl mercuric acetate (PMA) on the paint defacing fungus Aureobasidium pullulans have recently been reported using descriptive ultrastructure. We now report analyses of electron micrographs from a related study employing absolute volume determinations of whole cells and subcellular components of A. pullulans to which multivariate statistical analyses have been applied. Multivariate analysis was used to determine which subcellular components contributed most to differences between untreated and PMA treated cells, and to show relationships among those components.

Cultures of A. pullulans were grown in defined media for 48 hr at 28 C from washed blastospore inocula. Additional cultures were grown in identical media supplemented with threshold inhibitory levels of PMA (5x10-7 M). Conventional specimen preparation was used to obtain randomly oriented cell sections for examination with transmission electron microscopy. Cells treated with PMA showed dense surface membranes, a loss of microfilaments and lipid inclusions, and altered mitochondrial and nuclear envelope membrane organization compared with untreated cells (Figs. 1, 2).
Computer analysis of cell ultrastructure
Authors: Timms B. G. , Wilson D.W.
Published: June 2020

In animal tissues, the characteristic appearance of different cell types enables histologists and electron microscopists to identify a particular tissue. Uniformity of cell structure represents a dynamic morphological equilibrium dependent on the influences of cellular metabolism, the extracellular milieu and tissue specific messages from the nucleus. Using stereological techniques. Loud (1968) has demonstrated that these structural equilibria exist in normal rat liver parenchymal cells. Although stereology is widely used to provide a numerical description of the geometrical properties of cells and organelles (Weibel & Bolender, 1973), little attention has been given to devising a comparable scheme for qualitative aspects of morphology.

This report concerns the development of an –Identicel— reference library of pictorial representations used to categorise the salient features of different organelles with respect to their morphological variation. An important feature of this development has been the optimisation of the number and type of descriptive elements which would, in our opinion, provide useful information.
Immunoenzymatic demonstration of the simultaneous presence of transferrin, hemopexin and albumin in a same hepatocyte and their ultrastructural localization
Authors: Kraemer M. , Foucrier J. , Vassy J. , Chalumeau M.T.
Published: June 2020

Some authors using immunofluorescent techniques had already suggested that some hepatocytes are able to synthetize several plasma proteins. In vitro studies on normal cells or on cells issued of murine hepatomas raise the same conclusion. These works could be indications of an hepatocyte functionnal non-specialization, meanwhile the authors never give direct topographic proofs suitable with this hypothesis.

The use of immunoenzymatic techniques after obtention of monospecific antisera had seemed to us useful to bring forward a better knowledge of this problem. We have studied three carrier proteins (transferrin = Tf, hemopexin = Hx, albumin = Alb) operating at different levels in iron metabolism by demonstrating and localizing the adult rat hepatocytes involved in their synthesis.

Immunological, histological and ultrastructural methods have been described in a previous work.
The resolution of individual protein subunits in ferritin
Authors: Massover William H.
Published: June 2020

The technique of negative staining has been of very great value for directly determining the quaternary structure of individual multimeric proteins and viruses. In this regard, the iron-storage protein,, ferritin, is a notable exception for not having had its subunits unambiguously resolved by negative staining. Each ferritin molecule (d= 120Å) has an outer shell of 24 protein subunits (MW= 18,500) surrounding a variable amount of mineralized iron; published x-ray diffraction studies have not yet defined individual monomers in the polymeric shell. Claims that single subunits have been visualized in ferritin by electron microscopy (e.g.,6) all appear to be of highly doubtful validity since the phase granularity of the dried stain and supporting film has the same dimension as the presumed subunits; apparent subunits are readily visualized in defocused images, but are no longer discernable when brought closer to exact focus.
Visualization of thermally denatured nucleosomes
Authors: Poon N. H. , Seligy V. L.
Published: June 2020

Electron images of biological specimens composed of periodic structures are generally spurious. The reason is that unit structures may superimpose along the direction of view, and a “see through” image is formed especially from negatively stained and unstained objects. Methods to detail features of such objects from two dimensional images included optical and computer processing or combination of optical Fourier transformation and filtering. However, rotational superimposition may be employed when objects have simple symmetry.

We described here the use of stroboscope illumination photography (stroboscopy) to demonstrate the distribution of globular units along nucleoprotein fibers of thermally denatured mononucleosomes. The information was further used to predict the structure of intact nucleosomes as seen from bright field (BF) and dark field (DF) electron micrographs.

We previously obtained coSnsitometric scans from high resolution DF electron micrographs of partially relaxed unstained nucleosomes isolated from nuclease (EC. 3.1.4.7) digested goose erythrocyte nuclei and showed the presence of high density, periodic, contiguous globular regions (3-4 nm) along the DMA moiety.
Ultrastructural localization of specific nucleoprotein fractions
Authors: Brown G. L.
Published: June 2020

Bismuth (Bi) stains nucleoproteins (NPs) by interacting with available amino and primary phosphate groups. These two staining mechanisms are distinguishable by glutaraldehyde crosslinking (Fig. 1,2).

Isolated mouse liver nuclei, extracted with salt and acid solutions, fixed in either formaldehyde (form.) or gl utaraldehyde (glut.) and stained with Bi, were viewed to determine the effect of the extractions on Bi stainina. Solubilized NPs were analyzed by SDS-polyacrylamide gel electrophoresis.

Extraction with 0.14 M salt does not change the Bi staining characteristics (Fig. 3). 0.34 M salt reduces nucleolar (Nu) staining but has no effect on interchromatinic (IC) staining (Fig. 4). Proteins responsible for Nu and glut.- insensitive IC staining are removed when nuclei are extracted with 0.6 M salt (Fig. 5, 6). Low salt and acid extraction prevents Bi-Nu staining but has no effect on IC staining (Fig. 7). When nuclei are extracted with 0.6 M salt followed by low salt and acid, all Bi-staining components are removed (Fig. 8).
The structure of the tubulin heterodimer in zinc-induced sheets
Authors: Baker Timothy S. , Amos Linda A.
Published: June 2020

The structure of negatively stained zinc-induced tubulin sheets has been studied in projection by minimum beam microscopy and image processing. Figure (a) shows a typical sheet image, displaying the characteristic and prominent protofilament structure. The bar represents 500 nm. Figure (b) is an enlargement of part of (a).

Optical diffraction patterns (Figure c) reveal an orthogonal unit cell lattice of about 9.7 nm X 8.2 nm. The 8.2 nm repeat arises from the arrangement of heterodimers in the protofilaments, and is the first observation of such a repeat in sheet aggregates. It is only observed consistently in diffraction patterns from images recorded by minimum beam methods (1,000-2,000 e/nm2) and arises from small, but reproducible, structural differences between two similar subunits believed to represent the two chemical species of tubulin monomer (55,000 M.W.). At higher electron doses (10,000-20,000 e/nm2), the additional information is lost or very much reduced, and only a repeat of 4.1 nm is observed, owing to the loss of distinction between adjacent monomers in the protofilaments.