bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of Scanning Transmission and Backscattered Electron Imaging in the Sem, Using Heavy Metal Stained Sections of Biological Tissue
Authors: DeNee Phillip B. , Frederickson Richard G. 
Published: June 2020

The Transmission Electron Microscope (TEM) has been used extensively for the study of biological tissues in thin section (50-100 nm). For sectioned material greater than 100 nm, the Scanning Transmission Electron Microscope (STEM) and the High Voltage Electron Microscope (HVEM) have become the only alternatives for the study of these tissues at a resolution better than that obtained with the light microscope. Recently, it has been shown(1) that tissue stained with heavy metal can be studied in the Scanning Electron Microscope (SEM) by Backscattered Electron (BSE) imaging to give results similar to those obtained with the TEM. Because BSE imaging is a method complementary to STEM, it seemed worthwhile to compare the two techniques using the same specimens and beam conditions.Direct observation of the total specimen is possible with BSE imaging without interference by grid bars. Therefore, an improved perspective of tissue-totissue structural relationships can be obtained at a resolution significantly better than that of the light microscope.
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.
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).
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.
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 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.
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.
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).