bluuebunny/crossref_metadata_2025 huggingface dataset:
Applications of Photoelectron Microscopy
Authors: Baxter William J.
Published: June 2020

In this form of electron microscopy, photoelectrons emitted from a metal by ultraviolet radiation are accelerated and imaged onto a fluorescent screen by conventional electron optics. image contrast is determined by spatial variations in the intensity of the photoemission. The dominant source of contrast is due to changes in the photoelectric work function, between surfaces of different crystalline orientation, or different chemical composition. Topographical variations produce a relatively weak contrast due to shadowing and edge effects.

Since the photoelectrons originate from the surface layers (e.g. ∼5-10 nm for metals), photoelectron microscopy is surface sensitive. Thus to see the microstructure of a metal the thin layer (∼3 nm) of surface oxide must be removed, either by ion bombardment or by thermal decomposition in the vacuum of the microscope.
Keratohyalin Bodies in Ruminal Epithelium, Demonstrated by Ferric Ferricyanide Reduction Test
Authors: Vallejos Rodolfo E. , Vivas Jesus
Published: June 2020

Lately we have reported keratohyalin bodies of nuclear origin in the flat superficial cells of bovine ruminal epithelium; apparently this origin is based on a chromatin condensation, which includes light inner vacuoles, acquiring a spherical or semilunar shape. In order to demonstrate the keratohyalin content in these bodies, we have adapted the Chévremont & Fréderic ferric ferricyanide test - for proteins containing thiol groups - to the electron microscope histochemistry.

Biopsies of ruminal papillae were taken from three adult bovines, few minutes after their sacrifice; small samples of tissue were fixed during four hours in cold 2.5% formaldehyde and 0. 2 M cacodylate buffer at pH 7.4. After fixation, the tissue blocks were rinsed overnight at 4°C in several changes of 0.2 M cacodylate buffer containing 0.22 M sucrose.
A Study of the Ultrastructure of Visual Cell Outer Segment Membranes, Using a Water-Miscible Embedding Medium and Differential Staining
Authors: Godfrey Anthony J.
Published: June 2020

Aldehyde-fixed chick retina was embedded in a water-containing resin of glutaraldehyde and urea, without dehydration. The loss of lipids and other soluble tissue components, which is severe in routine methods involving dehydration, was thereby minimized. Osmium tetroxide post-fixation was not used, lessening the amount of protein denaturation which occurred. Ultrathin sections were stained with 1, uranyl acetate and lead citrate, 2, silicotungstic acid, or 3, osmium vapor, prior to electron microscope examination of visual cell outer segment ultrastructure, at magnifications up to 800,000.

Sections stained with uranyl acetate and lead citrate (Fig. 1) showed that the individual disc membranes consisted of a central lipid core about 78Å thick in which dark-staining 40Å masses appeared to be embedded from either side.
Ultrastructural Changes of Smoooth Endoplasmic Reticulum in the Retinal Pigment Epithelium by Choline Chloride
Authors: Hirosawa Kazushige , Yamada Eichi
Published: June 2020

The pigment epithelium is located between the choriocapillary and the visual cells. The pigment epithelial cell is characterized by a large amount of the smooth endoplasmic reticulum (SER) in its cytoplasm. In addition, the pigment epithelial cell of some lower vertebrate has myeloid body as a specialized form of the SER. Generally, SER is supposed to work in the lipid metabolism. However, the functions of abundant SER and myeloid body in the pigment epithelial cell are still in question. This paper reports an attempt, to depict the functions of these organelles in the frog retina by administering one of phospholipid precursors.
Human Breast Cancer: A Survey of Virus or Virus-Like Particles from Metastatic Nodules
Authors: Swedo John L. , Watson John H. L. , Talley R. W.
Published: June 2020

The literature is limited in its reporting of viral agents being found in solid tumor masses of human mammary cancer origin. In this continuing study of solid tumor masses, from intradermally located metastatic nodules of human breast cancer, particles have been seen which strongly resemble viruses. Their ultrastructural morphology is varied, leading to a large variety of particle types which present problems of interpretation. The present communication constitutes a survey of the variety of these particles which may represent viruses, the cytological conditions under which they are found and their relationship to the neoplastic cells.

The first general group of particles are characterized by a single dense outer membrane and a dense inner core separated from the outer membrane by an electron lucent area (Fig. 1).
Electron Microscopic and Isozyme Study of a Case of Ochronosis
Authors: Cha Jay W. , Melnick Perry J.
Published: June 2020

Hereditary ochronosis in very few cases has been examined electron microscopically or histochemically. In this disease homogentisic acid, a normal intermediary of tyrosine metabolism, forms in excessive amounts. This is believed to be due to absence or defective activity of homogentisic acid oxidase, an enzyme system necessary to break the benzene ring and to further break it down to fumaric and acetoacetic acids. Ochronotic pigment, a polymerized form of homogentisic acid, deposits mainly in mesenchymal tissues. There has been a question whether the pigment originates from the collagenous tissues, or deposits passively, where in contrast to melanin it induces degenerative changes.
Effect of Fire-Retardant Treatment on the Structure of the Cotton Fiber
Authors: Goynes W. R. , Muller L. L. , Boylston E. K.
Published: June 2020

The production of textile materials with reduced flammability is a research goal necessitated by the desire to reduce accidental burnings, as well as the need to meet increasingly strong legislative regulations. Cotton is normally a flammable material. A suitable fire-retardant treatment must give the fabric resistance to flaming and afterglow without detracting from the desirable natural properties of the cotton fiber. Generally, phosphorus-containing materials are very effective fire retardants. In situ polymerization of phosphorus-containing polymers on the surface and within a fiber is a practical means of imparting some degree of fire-retardancy.

Tris(hydroxymethyl)phosphonium hydroxide (THPOH) can be formed from the reaction of tetrakis(hydroxymethyl)phosphonium chloride with sodium hydroxide.
Localization of Adenosine Triphosphatase Activity in the Phleom of Nicotiana Tabacum
Authors: Cronshaw James , Gilder Jamison E.
Published: June 2020

Adenosine triphosphatase (ATPase) activity has been shown to be associated with numerous physiological processes in both plants and animal cells. Biochemical studies have shown that in higher plants ATPase activity is high in cell wall preparations and is associated with the plasma membrane, nuclei, mitochondria, chloroplasts and lysosomes. However, there have been only a few ATPase localization studies of higher plants at the electron microscope level. Poux (1967) demonstrated ATPase activity associated with most cellular organelles in the protoderm cells of Cucumis roots. Hall (1971) has demonstrated ATPase activity in root tip cells of Zea mays. There was high surface activity largely associated with the plasma membrane and plasmodesmata. ATPase activity was also demonstrated in mitochondria, dictyosomes, endoplasmic reticulum and plastids.
The Fine Strutcure of Lipoprotein Inclusion Bodies in Catfish Liver
Authors: Pool Charlotte R. , Hinton David E.
Published: June 2020

This preliminary report, concerned with the structural description of parenchymal cell inclusion bodies presently believed to contain lipoprotein complexes, is part of a study being conducted on the effects of heavy metal ions on tissues in channel catfish (latalurus punatatus).

Young adult channel catfish, 90-120 g, approximately 25 cm long, were perfused via the proximal aorta with phosphate buffered 4% glutaraldehyde and postfixed with 1% osmium in phosphate buffer. Tissues were dehydrated in ethyl alcohol and embedded in Epon 812. Thin sections were stained with uranyl acetate and lead hydroxide and examined with a Philips 200. One micron thick sections were oxidized with HPSA (10% hydrogen peroxidesulfuric acid) and stained with H&E or light green. The Schiff's method was also performed.
The Identification of Microglia and its Response to Injury
Authors: Baldwin Frank
Published: June 2020

Whilst there is general agreement upon the ultrastructure of astrocytes and oligodendrocytes, characterisation of microglia in healthy adult brain has remained uncertain.

Light microscopy of silver stained cat cerebral cortex revealed microglia close to neurons and blood vessels and sometimes remote from either.

A similarly situated glial cell did not conform to ultrastructural criteria for macroglia; it was identified as microglia. It was often fusiform in shape and when compared with astrocytes and oligodendrocytes, at low magnification, was intermediate in density. Intervening astrocyte cytoplasm often separated microglia from neurons and blood vessels.

Clumped chromatin was distributed around the periphery of the elongated nucleus. Cytoplasm was predominantly polar in distribution. Elongated endoplasmic reticulum was often oriented along the longitudinal axis of the cell; the cisternae contained material of greater density than the surrounding cytoplasmic matrix. The outer surface of the endoplasmic reticulum was irregularly studded with ribosomes.
Spatial Resolution of SEM Signals
Authors: Soezima H.
Published: June 2020

There are few investigations discussed on resolution of the signals as spatial resolving power, at the scanning electron microscope analysis. There remains misunderstanding that better resolution is obtained only by making a primary electron beam diameter small. At the scanning electron microscope analysis, there are such signals as secondary electron, back scattered electron, absorbed electron, transmitted electron, auger electron, cathode luminescence and X-rays. The spatial resolutions of these signals are effected not only by primary electron diameter but also by accelerating voltage, sample density, electro conductivity of the sample, surface condition of the sample, relative position among the primary electron optics, sample and detection system, energy of the signals, potential and magnetic distribution, and current density distribution of primary electron beam.

Some examples of the X-rays, that have the poorest resolving power in the signals, are shown below.
Quantitative Stereoscopy in the HVEM
Authors: Thomas L. E.
Published: June 2020

It is a common misconception that electron stereoscopy is suited only for viewing or measuring simple 3-D structures whose image details seldom overlap. Stereo pairs showing complex structures in 1 to 5 μm thick specimens at 1000 kV demonstrate otherwise. In fact, such structures can hardly be interpreted without stereo viewing.

To analyze structures observed in the USS 1000 kV microscope several quantitative stereoscopic methods have been developed. These methods have been used mainly to measure dislocations, precipitates, cavities, grain boundaries, etc. in metals, but they apply equally well to biological structures.

Parallax Measurements (floating spot method): The measurement of parallax for determining heights is done with a mirror stereoscope equipped with a “floating spot” device and a pantograph table for translating the stereo pair. In the Hilger-Watts stereoscope (Fig. 1) the floating spots are light spots which enter the optical paths to the two pictures through halfsilvered mirrors, giving the impression of a single spot at some height within the stereo model.
Analysis of Dark-Field Images of Disordered Materials
Authors: Cowley J. M.
Published: June 2020

Recently a number of authors have reported detail in dark-field images obtained from diffuse-scattering regions of electron diffraction patterns. Bright spots in images from short-range order diffuse peaks of disordered binary alloys have been interpreted as evidence for the existence of microdomains of ordered lattice or of segragated clusters of one component. Spotty contrast in dark field images of near-amorphous materials has been interpreted as evidence for the existense of microcrystals. Without a careful analysis of the imaging conditions such conclusions may be invalid. Usually the conditions of the experiment have not been specified in sufficient detail to allow evaluation of the conclusions.

Elementary considerations show that even for a completely random arrangement of atoms the statistical fluctuations of density will give a spotty contrast with spots of minimum diameter determined by the dark field aperture size and other factors influencing the minimum resolvable distance under darkfield imaging conditions, including fluctuations and drift over long exposure times (resolution usually 10Å or more).
Direct Observation of the Phase Separated Microstructure of a Sodium Borosilicate Glass and Its Development During Heat Treatment
Authors: Imeson D. , Vander Sande J. B.
Published: June 2020

By treating Corning code 7740 sodium borosilicate glass (composition by weight 80.5% SiO2, 13% B2O3, 3.8% Na2O, 2.2% Al2O3, 0.4% K2O) with a process consisting of heat treatment within the immiscibility region followed by a chemical etch, it is possible to produce a thin surface layer on the glass giving a low total optical reflectivity over the entire visual spectrum. In the course of a full investigation into this phenomenon, an attempt has been made to fully characterize the nature and development of the two-phase structure produced by the heat treatment.

Coupons of glass 3 x 3 x 0.125 inches, as received from Corning Glass Works, were heated for times ranging between 1-1/2 and 1000 hours at 600°C (well below the phase transition temperature, about 650°C for this glass). It is known that a three-hour heat treatment maximizes the antireflective property. Electron microscope specimens were conventionally prepared by mechanical grinding and ion thinning. However, after ion thinning, specimens were chemically etched by floating them on a drop of 0.1 wt% NH4.HF in 1.6N HNO3 solution, for typically 2 to 5 minutes. Specimens were rinsed by repeated flushing with distilled water, dried, and then carbon coated to prevent charging effects.
Phase Identification in TiB2-Ni Composites by Analytical Electron Microscopy
Authors: Sklad P. S. , Bentley J. , Fisher A. T. , Lehman G. L.
Published: June 2020

The transition metal diboride TiB2 is characterized by high hardness and high melting point (3253 K) . These properties make this material attractive for applications such as valve components in coal liquefaction plants and cutting tools. Liquid phase hot pressing using nickel as the fluidizing medium allows densification at lower temperatures than when using TiB2 powders alone, but the nickel and TiB2 react to form a complex multiphase microstructure. The purpose of this investigation was to identify the nickel-rich binder phase. The material examined was taken from a cylindrical compact hot pressed at ∼1720 K. During pressing most of the original 15 mol % Ni exuded from the initial mixtures. Specimens 3 mm dia were prepared for analytical electron microscopy (AEM) examination by mechanical lapping followed by ion milling.

A typical microstructure of the TiB2-Ni composite examined at 120 kv by conventional transmission electron microscopy (TEM) is shown in Fig. 1. The microstructure is characterized by TiB2 grains bonded by a second phase which was observed at multiple grain intersections. X-ray energy dispersive spectroscopy (EDS) measurements were made using a Philips EM400T/FEG. probe sizes of ∼10 nm dia and probe currents of ∼5 nA were used so that measurements could be made in thin regions of the binder phase, where beam broadening was small. Typical x-ray spectra from an intergranular region and an adjacent TiB2 grain are shown in Fig. 2. The results of standardless quantitative analyses of binder phase spectra indicated a composition (for Z > 11) of at least 95% Ni.
Inelastic Electron Scattering Spectroscopy of Graphite Intercalation Compounds
Authors: Ritsko John J.
Published: June 2020

In recent years graphite intercalation compounds have been the focus of much research because of their unique properties as a testing ground for fundamental studies of electrical and electronic properties, structural properties and phase transitions in quasi-two-dimensiona1 systems which are capable of a great deal of manipulation and control. The range of possible intercalation compounds is indicated in Figure 1. These materials consist of n layers of carbon atoms, covalently bonded within the plane in the usual graphite honeycomb lattice, between which are inserted planes of intercalants labeled X. The number of graphite layers, n, determines the stage of the compound. Well characterized compounds up to stage 5 or 6 can be easily prepared. X-ray and electron diffraction have been widely used to understand the structure of these compounds but many questions remain to be answered. This paper will concentrate on the fact that the intercalant always transfers charge to the graphite, acting either as an acceptor or a donor. Inelastic electron scattering spectroscopy has been used to study the electronic structure of the intercalant compounds and how it differs from graphite, as well as to determine the amount of charge transfer and the Fermi level position.
Inelastic Electron Scattering with Energy Losses in the meV-Region
Authors: Geiger J.
Published: June 2020

Inelastic scattering processes of electrons can be classified according to the amount of energy transferred during the scattering process. High-energy losses (E≳100eV) are coupled with the excitation of electrons out of inner shells of the atoms. The study of these energy losses are presently of great interest because they are characteristic for the chemical elements and, therefore, are suitable for a chemical analysis of the specimen. In addition the “fine structure” superimposed to the high-energetic wing gives information about the short-range order around the atom involved in the scattering process. Medium-energy losses (E≃10eV) are caused by excitation of valence-band transitions, plasmons.or surface plasmons. Analogous longitudinal modes exist also in insulators. For energy losses with very low energies (E<leV) mostly lattice vibrations (phonons) are responsible, but the situation is more complex as explained in the following.

A theory, which describes the energy losses in the low-energy range very well, is the dielectric theory. In this theory the dynamical behaviour of the solid is included in the frequency- and wave-number-dependent dielectric function.
Direct Observation of the Surface Topography of Single Crystals in a Transmission Electron Microscope
Authors: Lehmpfuhl G. , Uchida Y.
Published: June 2020

From the analysis of convergent-beam electron diffraction patterns it is well known that the intensity of some reflections may become most sensitive to the crystal thickness variation at special conditions for thickness and orientation. This can be understood as a dynamic effect as well as a kinematic effect of electron diffraction. Using such a diffracted beam for imaging, a small change in thickness of a single crystal can be observed in an electron microscope. At the beginning of the application of this technique only weak beams were used for imaging the surface topography of undistorted single crystals. Thickness differences down to the atomic level could be detected in darkfield micrographs of MgO and Au. However, the intensity of the weak beams was so low that long exposure times up to 2 minutes were necessary to record a micrograph at a magnification of 20,000. This magnification is the upper limit for the weak-beam darkfield technique for reasons of stability of the electron microscope. The thickness contrast can be explained already by the kinematical theory of electron diffraction.
Near-Surface Dislocations in NiO
Authors: Ostyn K.M. , Carter C.B.
Published: June 2020

The appearance of strong-beam images of near-surface screw dislocations in stainless steel has been discussed by Howie and Whelan who showed that the contrast in strong-beam bright-field and dark-field images of such dislocations were pseudo-complementary in a manner analogous to the more familiar stacking-fault fringe contrast. This observation was explained using the concept of anomalous absorption. The screw dislocations were left behind by edge dislocations gliding in the thin foil and were assumed to prevented from slipping out of the foil by the oxide layer on the foil surface. In this paper it will be shown that strong-beam images of edge dislocations trapped near the surface of NiO foils show similar contrast. In addition a clear difference in the intensity of the corresponding weak-beam images recorded using ± g has been found. The unusally strong contrast which is possible in weak-beam images of these near-surface dislocations has also been reported by Little et al.
Considerations of the Transmission of a Small Electron Probe Through a TEM Foil and Its Relation to Characteristic X-Ray Spatial Resolution
Authors: Imeson D. , Vander Sande J. B.
Published: June 2020

It is well established that when an electron beam is incident upon a thin foil in the form of a focused probe, as in STEM, multiple scattering events in the sample cause considerable lateral spreading of the electron beam. The volume of material excited by the electron beam is therefore much greater than that volume defined by simple projection of the incident beam through the sample. In the application of the techniques of quantitative X-ray analysis in STEM to regions of composition variation with small spatial extent this point becomes of crucial importance, being the main determinant of the ability to map such composition changes, or even to detect them. It is the view of the authors that there exists some confusion over the nature of the beam spreading phenomenon in thin foils of crystalline material and the concept of spatial resolution of composition determination by characteristic X-ray emission. We intend here to clarify these concepts by discussing the meaning and use of the term “beam broadening” in analytical transmission electron microscopy.
Interface Structure of Some Precipitates in Austenitic Stainless Steels
Authors: Bentley J.
Published: June 2020

Interphase boundaries often play a dominant role in high-temperature materials properties such as deformation and fracture or radiation damage. A detailed knowledge of the interfacial structure is required to understand the relationship between microstructure and properties. High-resolution TEM observations have been made of the interfacial structure of two carbides (M23C6 and MC) and an intermetallic compound (sigma) in 300 series austenitic stainless steels.Precipitates with well-defined orientation relationships and interface planes were chosen in order that the determined structures would be generally applicable in a range of property-structure correlations.

Chromium-rich M23C6 (τ) is a face-centered cubic (fcc) phase with a lattice parameter (ao)τ ∼ 1.06 nm ≈ 2.97(ao)γ which forms with a cube-on-cube orientation relationship with the matrix (γ) and with {111} and {110} interfaces. In order to accommodate the “mismatch” of ∼1% between the matrix and precipitate, interface dislocations with separations of 10—20 nm are expected and have been observed previously.
Microstructures of Laser Processed Fe-Cr Surface Alloys
Authors: Molian P. A. , Khan K. H. , Wood W. E.
Published: June 2020

In recent years, the effects of chromium on the transformation characteristics of pure iron and the structures produced thereby have been extensively studied as a function of cooling rate. In this paper, we present TEM observations made on specimens of Fe-10% Cr and Fe-20% Cr alloys produced through laser surface alloying process with an estimated cooling rate of 8.8 x 104°C/sec. These two chromium levels were selected in order to study their phase transformation characteristics which are dissimilar in the two cases as predicted by the constitution diagram. Pure iron (C<0.01%, Si<0.01%, Mn<0.01%, S=0.003%, P=0.008%) was electrodeposited with chromium to the thicknesses of 40 and 70μm and then vacuum degassed at 400°F to remove the hydrogen formed during electroplating. Laser surface alloying of chromium into the iron substrate was then performed employing a continuous wave CO2 laser operated at an incident power of 1200 watts. The laser beam, defocussed to a spot diameter of 0.25mm, scanned the material surface at a rate of 30mm/sec, (70 ipm).
Vacancy-Assisted Precipitation in a 18 W/O Cr - 10 W/O ni - 0.3 W/O P Steel
Authors: Pelton A. R.
Published: June 2020

Although many similarities exist in the precipitation behavior in ferritic and austenitic steels, the nucleation and growth mechanisms in these systems have eluded full comprehension. However, it is apparent that the initial clustering of substitutional and interstitial atoms can dictate the structure and orientation relationships of subsequent phases. Hence, in order to realize the benefits of these decomposition transformations, a better understanding of the incipient nucleation event is imperative. Therefore, a transmission electron microscopy study of a quenched-aged 18-10 stainless steel doped with 0.3 w/o P was undertaken as part of a more comprehensive research program. The precipitation reactions in this austenitic stainless steel were originally surveyed by Rowcliffe and Nicholson [1] and Rowcliffe and Eyre [2], These investigators observed a variety of defects ranging from vacancy defects on {100} planes at lower aging temperatures to Cr3P laths with {100} habit planes at higher aging temperatures.
Ultrastructure of Breast Cancer Cells in Aggregate Cultures
Authors: Seman G. , Cynthia Edwards
Published: June 2020

The culture of carcinoma cells in histiotypic aggregates floating free in medium is currently receiving increased attention. The methods used rely on mechanical agitation on rocker or rotary platforms. But mechanical agitation is technically cumbersome and interferes with spontaneous aggregation and organization of the cells by mutual recognition. Epithelial cells were long known of being unable to adhere to agar and we used this phenomenon to grow breast cancer cells in stationary cultures in agar-inlaid, conventional plastic flasks. In this way the cells formed floating aggregates which revealed important features by light and electron microscopy.

Corning T25 and T75 flasks were inlaid with 5-6 mm thick layer of 1.5% purified agar boiled in distilled water and sterilized. Once the agar has settled an equal amount of medium (L15 with 10% fetal calf serum but no antibiotics) was added and the flasks incubated for 5 days at 37°C. This allowed time for medium to soak the agar and for contamination to be detected.
Progressive Reduction of Pseudopodia in Advancing Grades of Uterine Cervical Intraepithelial Neoplasia (CIN) - An Application of a New Morphometric Method
Authors: Okagaki T. , Clark B.A. , Twiggs L.B.
Published: June 2020

It has been suggested that stroma epithelial interaction may play a significant role in epithelial differentiation and carcinogenesis. Squamous epithelium normally possesses pseudopodia (foot processes) which protrude in the underlying stromal tissue. Whether the pseudopodia facilitate the communication between the epithelium and stroma is an open question. Nevertheless, it has been demonstrated by a semi-quantitative observation that the number of pseudopodia on the basal cells of the advanced premalignant condition (carcinoma in situ or grade 4 cervical intraepithelial neoplasia (CIN)) of the uterine cervix was reduced.

We have developed a method to measure the number of pseudopodia on the basal cells of the epithelium, their cross sectional widths, and the cross section widths of basal cells appearing in transmission electron micrographs. First on each observed basal cell, the number of pseudopodia is calculated from formula derived by probabilistic (morphometric) calculation:
Regulation of Microtubule Assembly-Disassembly in Mitotic Mammalian Cells: Role of Calcium, Calmodulin and MTOCs
Authors: Brinkley B. R. , Brenner S. L. , Pepper D. A. , Pardue R. L.
Published: June 2020

Two microtubule arrays exist in cultured mammalian cells during their progression through the cell cycle; the cytoplasmic microtubule complexes (CMTC) of interphase cells (Figure 1) and the mitotic apparatus (MA) of dividing cells (Figure 2). As chromosomes are segregated to opposite poles of the spindle during telophase, the microtubules of the MA are disassembled. During late telophase -G1 phase the tubulin subunits from the spindle are recycled into the microtubules of the CMTC which forms an elaborate network throught the cytoplasm. When cells progress into late G2 -Prophase, the CMTC is disassembled and the tubulin is converted into microtubules of the MA. our research has been aimed at defining the mechanism whereby cells regulate the alternating patterns of microtubule assembly-disassembly during the cell cycle.

In one series of experiments, we have investigated the role of calcium in microtubule assembly. Several laboratories have shown that cytoplasmic and spindle microtubules are unstable in the presence of elevated free calcium levels. Using monospecific antibodies and indirect immunofluorescence, we have demonstrated the presence of the ubiquitous calcium-binding protein calmodulin in the mitotic spindle of mammalian cells in vitro (Figure 3).
Dipyridamole Rescue of Venom Injected Dogs
Authors: June Marshall G. , Ruiz C. , Swanson S. , Shaeffer R.C.
Published: June 2020

The endothelia are vulnerable to a number of non-physiologic and toxic substances. Endothelial alterations induced by these substances often mimic diseases, i.e. atherosclerosis, which effect the cardio-vascular system.A series of experiments were designed to test the efficacy of dipyridamole, in inhibiting the destructive changes caused by rattlesnake venom (RSV).

In the first experiment, seven mongrel dogs, 18 - 27 kgs, were divided into two groups. Group one (G-l), five dogs, received RSV. Group two (G-2) was composed of two dogs used as controls and injected with normal saline. Following sedation, the animals were injected with venom or saline and at 1,3,5,15,30,45 and 60 mins after injection blood was obtained for platelet, blood elements and coagulation studies. At 5 and 60 mins, samples of the femoral arteries and veins were obtained for study with light and electron microscopy techniques.

In the control group (G-2), the luminal surface of the arteries had an undulated appearance with oval or spindle shaped protrusions (Figure 1) which are the nuclei of the endothelial cells.
Developing Elastic Fibers in the Chick Embryo
Authors: Basom C. R.
Published: June 2020

The tunica media of the developing chick aorta was examined for elastic fiber formation. Embryos of three to eighteen days incubation age were prepared for electron microscopy by Karnovsky's fixation. Small embryos were fixed by “in toto” immersion: medium sized embryos were previously transected. The aortae of larger embryos were removed prior to fixation. Epon 812 was used for embedment.

Irregular masses of amorphous ground substance appeared in the interstitial space of the aortae in three to five day embryos. These masses were located where elastic fibers would later form (Fig. 1). Later loose tangles of microfibrils appeared within the same masses (Fig. 2). In still older embryos, individual unit collagen fibrils appeared within this loose network. At one week's incubation, small elastic fibers could be identified by their homogeneous matrix. These arose within the conglomerate masses described above. At the beginning of the third week compact bundles of colinear unit collagen fibrils appeared (Fig. 3). These fibrils swelled, gradually lost their periodicity and became very lucid (Fig. 4).
Complex Vesicles, Microtubules, and Cytoplasmic Filaments in the Endothelial Cells of Normal Dog Aorta
Authors: Sun C. N. , Ghidoni J. J.
Published: June 2020

Endothelial cells in longitudinal and cross sections of aortas from 3 randomly selected “normal” mongrel dogs were studied by electron microscopy. Segments of aorta were distended with cold cacodylate buffered 5% glutaraldehyde for 10 minutes prior to being cut into small, well oriented tissue blocks. After an additional 1-1/2 hour period in glutaraldehyde, the tissue blocks were well rinsed in buffer and post-fixed in OsO4. After dehydration they were embedded in a mixture of Maraglas, D.E.R. 732, and DDSA.

Aldehyde fixation preserves the filamentous and tubular structures (300 Å and less) for adequate demonstration and study. The functional significance of filaments and microtubules has been recently discussed by Buckley and Porter; the precise roles of these cytoplasmic components remains problematic. Endothelial cells in canine aortas contained an abundance of both types of structures.
High Brightness Electron Gun Using a Field Emission Cathode
Authors: Broers A. N.
Published: June 2020

A field emission cathode electron gun with two stages of acceleration has been built in order to measure the electron beam brightness that can be produced in practice from a tungsten field emission cathode. The gun is similar to that reported by A. Crewe except that the accelerating electrodes are plane, rather than shaped, apertures, and the cathode is located by a gimbal mechanism which allows the cathode to be tilted over an arc of 70° in any direction and positioned laterally. The gun electrodes have been precisely machined with the apertures round within 0.25 micron and aligned with respect to each other to better than 10 micron. The second accelerating electrode is followed by scan plates, a test grid, and an electron detector which together allow the probe size to be measured in the usual scanning electron microscope mode.
Record Wear Studies by Scanning Electron Microscopy
Authors: Coutts M.D. , Levin E.R. , Woodward J.G.
Published: June 2020

While record grooves have been studied by transmission electron microscopy with replica techniques, and by optical microscopy, the former are cumbersome and restricted and the latter limited by lack of depth of focus and resolution at higher magnification. With its great depth of focus and ease in specimen manipulation, the scanning electron microscope is admirably suited for record wear studies.

A special RCA sweep frequency test record was used with both lateral and vertical modulation bands. The signal is a repetitive, constant-velocity sweep from 2 to 20 kHz having a duration and repetitive rate of approximately 0.1 sec. and a peak velocity of 5.5 cm/s.

A series of different pickups and numbers of plays were used on vinyl records. One centimeter discs were then cut out, mounted and coated with 200 Å of gold to prevent charging during examination. Wear studies were made by taking micrographs of record grooves having 1, 10 and 50 plays with each stylus and comparing with typical “no-play” grooves. Fig. 1 shows unplayed grooves in a vinyl pressing with sweep-frequency modulation in the lateral mode.
In Situ Electron Microscope Investigations of the Growth and Structure of Thin Films
Authors: Hutchinson Thos. E.
Published: June 2020

Few areas of investigation have benefited more from the use of the electron microscope than thin films. This is most strikingly demonstrated by the state of knowledge of the structure and growth mechanisms prior to and subsequent to electron microscope investigations.

The use of the electron microscope as an experimental chamber in which both growth and observation take place simultaneously, has been responsible primarily for the broad quasi-quantitative view of the process of formation of thin films we now hold. The great advantage of the in situ experimental arrangement lies in its ability to examine in detail the time sequence of events occuring during thin film nucleation and growth. Each stage in the process of formation of thin films has been examined, and although questions still remain as to the exact mechanisms involved, the general features are well characterized. These are nucleation of ad-atom clusters on the substrate, growth of the atom clusters both laterally and perpendicular to the substrate, coalescence of the nuclei into larger sub-units and finally, elimination of channels between the extended islands.
Application of Electron Diffraction to Problems in Biological Electron Microscopy
Authors: Glaeser R. M. , Thomas G. , Christensen R. , Brammer W. G.
Published: June 2020

The role of elastic (Bragg) scattering in relation to contrast and advanced electron microscopy of biological materials has not been investigated in the detail that is now common with inorganic crystals. It is the object of this paper to demonstrate the application of selected area diffraction, dark field imaging and low angle Fourier contrast to biological materials. Essential differences between the mechanisms of diffraction image-contrast are due to the larger lattice spacings in biological structures, which invariably result in Fourier image contrast. Crystals with spacings greater than 10Å can be expected to show Fourier contrast under normal microscope operations.

Samples of crystalline amino acids were grown by solvent evaporation on formvar coated specimen grids. Specimen grids were scanned and selected on the basis of appearance in a polarization-optical microscope (see Fig.1). All crystalline amino acids tested were extremely sensitive to damage in the electron beam.
Urinary stone analysis
Authors: Khan Saeed R.
Published: June 2020

Since crystalline composition of a urinary stone is an expression of urinary chemical conditions prevalent at the time of crystal nucleation and growth, a careful analysis of the stone and identification of constituent crystals is necessary for an understanding of the disease and the initiation of a proper medical regimen for the prevention of stone recurrence. Of the number of methods available, analytical electron microscopic techniques including scanning (SEM) and transmission electron microscopy (TEM), x-ray microanalysis (XRMA), and electron diffraction (ED) are gaining in popularity.

For SEM, the dried stone is fractured through the middle and small pieces representing different areas of the stone are mounted on a carbon planchet or an aluminum stub using a double sticky tape or graphite paint. The specimen is then sputter coated with silver, gold or gold/palladium; or coated with carbon. For morphological examination alone, the specimen can be coated with any of the available conducting substances, but for XRMA the specimen should either be examined uncoated or be coated with carbon, or with a substance whose peaks in the XRMA spectrum do not interfere with the peaks of the elements of interest.
Mass Accuracy in the STEM
Authors: Wall J. S.
Published: June 2020

The scanning transmission electron microscope (STEM) has a number of features which make it ideal for quantitative studies: 1) large acceptance angle scintillator-photomultiplier detectors for low dose dark field imaging with linear electron detection, 2) simple contrast transfer function with no oscillations, 3) cold stage for zero contamination and reduced mass loss, 4) digital scanning for accurate magnification and positioning and 5) serial readout of several signals simultaneously for direct interfacing to a computer.

For the past 10 years the Brookhaven STEM has been used for mass measurements on isolated individual molecules in freeze dried biological specimens. Interpretation of dark field STEM images is straightforward because of the clean background and linearity of the entire imaging process. Mass measurements provide a quantitative link to biochemical studies. Tobacco mosaic virus (TMV) usually is included along with the specimen of interest as a measure of the quality of the freeze drying and as a check on the microscope calibration, but is not necessary for absolute mass measurements.
Ultrastructure of Testicular Spermatozoon of the Fish Oreochromis Niloticus
Authors: Guha T. , Siddiqui A. Q. , Prentis P. F.
Published: June 2020

Tilapia, Oreochromis niloticus, is an economically important fish in Saudi Arabia. Elucidation of reproductive biology of this species is necessary for successful breeding program. In this paper we describe fine structure of testicular sperm cells in O, niloticus.

Testes from young adult fish were fixed in gluteraldehyde (2%) and osmium tetroxide (1%), both in cacodyl ate buffer. Specimens were processed in the conventional way for electron microscopy and thin sections of tissues (obtained by cutting the blocks with a diamond knife) were stained by ura- nyl acetate and lead citrate. These were examined in a Carl Zeiss electron microscope operated at 40 kV to 60 kV. Sperm cells were obtained from testes by squeezing them in cacodyl ate buffer. They were fixed in gluteraldehyde (2%) in the same buffer, air dried, gold coated and then examined in a Philips scanning electron microscope (SEM) operated at 25kV.

The spermatozoon of O. niloticus is consisting of head, midpiece and tail (Fig. 1).
Fine structure of early degenerating myofibers in the tibialis anterior of young ‘MDX’ mouse
Authors: Geissinger H.D. , McDonald-Taylor C.K.
Published: June 2020

A new strain of mice, which had arisen by mutation from a dystrophic mouse colony was designated ‘mdx’, because the genetic defect, which manifests itself in brief periods of muscle destruction followed by episodes of muscle regeneration appears to be X-linked. Further studies of histopathological changes in muscle from ‘mdx’ mice at the light microscopic or electron microscopic levels have been published, but only one preliminary study has been on the tibialis anterior (TA) of ‘mdx’ mice less than four weeks old. Lesions in the ‘mdx’ mice vary between different muscles, and centronucleation of fibers in all muscles studied so far appears to be especially prominent in older mice. Lesions in young ‘mdx’ mice have not been studied extensively, and the results appear to be at variance with one another. The degenerative and regenerative aspects of the lesions in the TA of 23 to 26-day-old ‘mdx’ mice appear to vary quantitatively.
Chlorotrifluoroethylene (CTFE) Oligomer: Effect on Livers of Fischer-344 Rats
Authors: Mattie D.R. , Chase M.R. , Kinkead E.R. , Whitmire R.E.
Published: June 2020

Chlorotrifluoroethylene (CTFE) oligomer is a nonflammable, saturated, hydrogen-free halocarbon oil with chain lengths of six to ten carbons. CTFE was seen to have a low degree of toxicity in acute toxicity tests. A subchronic study was conducted because CTFE is an excellent candidate hydraulic fluid. The objective of this electron microscopic investigation was to examine and compare the livers of male and female rats after inhalation exposure to CTFE for 90 days.

Male and female Fischer-344 rats were exposed to 0.25, 0.5, or 1.0 mg/L CTFE aerosol for 90 days, 6 h/day, 5 days/week. An equal number of control rats were exposed to air only. Following the 90-day exposure period, 10 male and 10 female rats were sacrificed from each group. A 1mm slice of the left lobe of the liver of three rats of each sex and each group was collected for transmission electron microscopic examination.
Calcium/phosphorus ratios of femurs of male and female fischer-344 rats exposed to halocarbon 27-S
Authors: Mattie D.R. , Maslanka J.J. , Flemming C.D.
Published: June 2020

Halocarbon 27-S (H 27-S) is a polymer of chlorotrifluoroethylene (CTFE). Since metabolism of CTFE yields inorganic fluoride, it was believed that H 27-S would also yield fluoride in the blood. Exposure to fluorine results in deposition in bone as calcium fluoride or fluorapatite. Deposition of fluoride in the bone matrix should result in an altered calcium phosphorus ratio (CaP). The objective of this study was to determine the CaP of femurs of male and female rats exposed subchronically to H 27-S using energy dispersive x-ray analysis techniques and to compare CaP from exposed rats with the CaP of control rats.

Male and female rats were dosed daily with 2.5 g H 27-S/kg body weight by gavage for 7 or 21 days. Rats were sacrificed at 7, 21 and 35 days (14 days after the 21 day dosing). Femurs of three rats of each sex and each group were analyzed.
Determination of ionization cross section by electron spectroscopic imaging
Authors: Simon G.T. , Heng Y.M. , Ottensmeyer F.P.
Published: June 2020

Electron energy loss spectroscopy (EELS) has become a significant technique for high resolution elemental microanalysis and mapping. Theoretically, quantitative analysis requires only one simple equation:

Eqn.(1)

where N is the number of atoms per unit area analysed; I(net)(a,δ) is the core loss intensity integrated over an energy range δ beyond the ionization edge and with a collection angle a; I(total) is the total intensity integrated beneath the whole spectrum; σ(a,δ) is the corresponding ionization cross section.

To obtain I(net) according to current convention and some theoretical justification, the simplest way of removing the background beneath an ionization edge is simply fitting at least two pre-edge measurements to the equation of I=AE-r, where I is the intensity of electrons that have energy loss E; A and r are constants to be determined from the fitted pre-edge region. Several other methods have also been derived for better accuracy in specific applications.
The use of image symmetry in the analysis of high-resolution image of grain boundaries in GaAs
Authors: Cho N.-H. , Carter C.B.
Published: June 2020

Atomic arrangements at grain boundaries in diamond-structure materials have in the past been theoretically examined most fully for the case of symmetrical interfaces. In particular, <110> tilt boundaries have been modelled in terms of a combination of units corresponding to a/2 [110] edge dislocation cores and symmetrical six-membered rings. Grain boundaries in materials with the sphalerite-structure have two different atomic arrangement for each corresponding grain boundary in the diamond-structure materials; these depend on the relative positions of group III and group V elements. Experimental studies have been carried out recently for twin boundaries, high-angle boundaries and low-angle boundaries of GaAs. This paper illustrates how the analysis of the atomic structure of grain boundaries in GaAs can be facilitated by using the symmetry of HREM images of neighboring Σ=3 coherent twin boundaries in a manner similar to that described earlier for individual stacking faults. Details of the sample preparation are described elsewhere. The orientation of the specimen was such that the electron beam was parallel to the common [110] tilt axis.
Determination of the lattice translation across {110} APBs in GaAs
Authors: Rasmussen D.R. , Cho N.-H. , Carter C.B.
Published: June 2020

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.