bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Energy Dependence of Radiation Damage in 1-Valine
Authors: Howitt D. G. , Glaeser R. M. , Thomas G. 
Published: June 2020

In the study of radiation sensitive materials in an electron microscope a limit to resolution is imposed when the number of electrons required to record an image is greater than the number required to destroy the specimen. This limitation is conveniently expressed in the equation due to Glaeser (1973):where d is the size of the object detail, c the contrast of the object feature, f the detection efficiency of the recording device and Ncr the critical exposure, is the number of electrons in unit area which will destroy the specimen.
Fluorocitrate Neural Dystrophy of the Guinea Pig Cochlea
Authors: Spector G.J. , Carr C.D. , Kaufman Arenberg I. , Maisel R.H. 
Published: June 2020

All studies on primary neural degeneration in the cochlea have evaluated the end stages of degeneration or the indiscriminate destruction of both sensory cells and cochlear neurons. We have developed a model which selectively simulates the dystrophic changes denoting cochlear neural degeneration while sparing the cochlear hair cells. Such a model can be used to define more precisely the mechanism of presbycusis or the hearing loss in aging man.Twenty-two pigmented guinea pigs (200-250 gm) were perfused by the perilymphatic route as live preparations using fluorocitrate in various concentrations (15-250 ug/cc) and at different incubation times (5-150 minutes). The barium salt of DL fluorocitrate, (C6H4O7F)2Ba3, was reacted with 1.0N sulfuric acid to precipitate the barium as a sulfate. The perfusion medium was prepared, just prior to use, as follows: sodium phosphate buffer 0.2M, pH 7.4 = 9cc; fluorocitrate = 15-200 mg/cc; and sucrose = 0.2M.
The Production of Neuroaxonal Dystrophy in the Lateral Vestibular Nucleus of Rats by Centrifugation
Authors: Johnson J.E. 
Published: June 2020

Very little is known about the effects of altered gravitational forces on the morphology of the central nervous system. Data so far published have been at the light microscopic level. The present abstract and corresponding article (in preparation) represent initial electron microscopic observations of changes in the lateral vestibular nuclei (VL) of rats centrifuged for varying lengths of time. Several groups of rats were employed in the study. Two groups were placed on a centrifuge (4.15 g's) at weaning and removed after 4 days. One group was conceived, born and raised on the centrifuge (4.15 g's) for 1 month. Other rats were placed on at weaning and left on for up to 21 months (2.76-4.l5 g's). All the centrifuged rats were sacrificed by aldehyde perfusion immediately after removal from the centrifuge.In the rat lateral vestibular nucleus, some synaptic terminals contain spherical (S) vesicles and others flattened (F) vesicles.
Cytoplasmic Cylinders Associated with the Nucleus and Cell Wall of Marchantia Spermatids
Authors: Kreitner G. L. 
Published: June 2020

Analysis of thin sections reveals that young spermatids of the liverwort Marchantia effect considerable thickening of their cell wall over a narrow range of spermatid development. Cells of only slightly different age can be identified by wall thickness and by their appearance in separate blocks, the cells of which are synchronous. On rare occasion in one block cytoplasmic cylinders appeared singly or in aggregates of many closely arranged, parallel cylinders (Fig. 1). Their long axes follow an oblique path through the cytoplasm, and they appear to penetrate the envelope of the nucleus at one end (Fig. 3) and merge with fibrogranular material of the spermatid wall at the other end (Fig. 4).Cytoplasmic cylinders average about 100 nm in diameter and have been measured at 0.6 microns in length. Tangential sections following the length of a cylinder show that its margin is regularly contoured in this plane, but smooth in transection (Fig. 2).
Transmission Electron Microscopy of Endometrium in Women Bearing Progesterone- Releasing Intrauterine Devices
Authors: González-Angulo A. , Aznar-Ramos R. , Ruiz de Chavez I. 
Published: June 2020

The addition of natural progesterone with a continuous daily release rate to inert intrauterine devices has resulted in a lower pregnancy rate and a reduced frequency of bleeding and expulsions. Light microscopy studies on these endometria have shown a suppressed or inactive pattern in addition to inflammatory infiltrate as well as a diffuse predecidual reaction with degenerative changes in most cases. The aim of the present study is to characterize at ultrastructural level the possible modifications seen in cell organelles in both epithelium and stroma resulting from a continuous release rate of progesterone.Twenty endometrial biopsies were taken; ten at day 10 ± 2 and ten at 20 ± 2 days of the menstrual cycle. Proliferative endometrium disclosed a paucity of cell organelles and it was similar to what has been described for inert devices (2). Secretory endometrium disclosed accumulation of light and dark glycogen in the cytoplasm (Fig. 1).
Tube-Foot Ultrastructure of an Ophiuroid Echinoderm
Authors: Hajduk S.L. 
Published: June 2020

The tube-feet of asteroids and echinoids, highly extensible tubular structures expanded distally into suckers, are important in gas exchange, locomotion, feeding and sense-reception. Their ultrastructure has been thoroughly examined. The less extensible, suckerless tube feet of ophiuroids have been shown to serve the same functions, but their ultrastructure has not been examined. I report here on ultrastructural features of the tube-feet of the ophiuroid Hemipholis elongata.The wall of the tube-foot is continuous with the water vascular system. The lumen of the tube-foot contains the same spherical hemoglobin-containing cells found elsewhere in the water vascular system. The innermost layer of the wall is composed of flagellated, choanocyte-like cells which form cytoplasmic extensions into the cavity of the tube-foot (Figure 3). Attachment of these cytoplasmic extensions to the hemoglobin-containing cells has been observed. Septate desmosome cell junctions are frequently seen in this inner epithelial layer and less frequently in the surface epithelial layer.
Auto-Correlation Analysis of High-Resolution Electron Micrographs of Near-Amorphous Thin Films
Authors: Fan G.Y. , Cowley J.M. 
Published: June 2020

Many electron micrographs of thin films of amorphous materials give the impression that small ordered regions are present (Fig. 1). However, for cases where little order exists it is difficult to decide whether small regular patches are indictions of ordering or just chance occurances. In order to quantitatively characterize the degree of local ordering of nearamorphous materials from information contained in this kind of micrographs, we have developed a new method in which 2-D auto-correlation functions are obtained from small image regions and then rotated relative to each other so that similar features coincide. By summing up of these auto-correlation functions, sane statistical information of the local orderig for the whole image is obtained.Under certain limiting conditions, the intensity distribution of electron micrographs may be related directly to the projection of the charge or potential distribution of a thin film [1]. Then the 2-D auto-correlation function is equivalent to a 2-D form of Patterson Function (PF), well known in X-ray crystallography in that it represents a map of inter-atomic vectors [2]. Fran different area of the image, PFs may be similar but have mutual rotations so that when they are added together, the orientation information is lost; only the Radial Distribution Function (RDF) is obtained (fig. 4). It is therefore necessary to do sane kind of alignment before the summation.
Electron Energy Loss Spectroscopy in a 400kV Transmission Electron Microscope
Authors: Oikawa T. , Bando Y. , Hosoi J. , Kokubo Y. , Naruse M. 
Published: June 2020

Electron energy loss spectroscopy (EELS) is a powerful technique to investigate the “electron and atom interaction in specimens.” EELS, as an elementary analysis tool, has the following advantages in a higher accelerating voltage transmission electron microscope (TEM):1)Multiple scattering disturbance decreases with increasing accelerating voltage, because the mean free path of plasmon scattering decreases.2)The signal background ratio (S/B) increases with increasing accelerating voltage, because the effective cut-off angle increases.This report introduces our newly developed electron energy analyzer, the ASEA40, used for the JEM-4000EX 400kV TEM, and presents experimental results that verify its advantages.Fig.1 shows the block diagram of the ASEA40 attached to the JEM-4000EX with the ASID40 and the computer of the EDS system.
A Sampling Device For Acquisition of Negatively Stained Clinical Specimens
Authors: Bozzola John J. 
Published: June 2020

Transmission electron microscopists have used the negative staining technique for the rapid identification of viral particles in clinical samples for nearly forty years. Occasionally, it was the only laboratory procedure available until appropriate cultural or serological procedures were developed for the particular virus.Specimens for negative staining may be classified as either directly collected fluids (urine, vesicle fluid, serum, cerebral spinal fluid, tears, nasal secretions, washings from various lesions or body sites), or suspensions in physiologically balanced solutions (suspensions of disrupted cells or semisolid materials as excreta or pus). The technique for specimen preparation usually consists of depositing the fluid specimen onto a coated grid followed by the application of a drop of stain. It is also possible to mix the fluid with stain prior to deposition on the grid. Most often specimens must be collected and transported some distance over variable periods of time in order to perform the procedure. In the laboratory, trained technicians process the specimens and carefully manipulate the fragile coated grids using jeweler's forceps that often become contaminated with infectious material.
Electrostatic optics and aberration correction in the 1940s and today
Authors: Rempfer Gertrude F. 
Published: June 2020

I became involved in electron optics in early 1945, when my husband Robert and I were hired by the Farrand Optical Company. My husband had a mathematics Ph.D.; my degree was in physics. My main responsibilities were connected with the development of an electrostatic electron microscope. Fortunately, my thesis research on thermionic and field emission, in the late 1930s under the direction of Professor Joseph E. Henderson at the University of Washington, provided a foundation for dealing with electron beams, high vacuum, and high voltage.At the Farrand Company my co-workers and I used an electron-optical bench to carry out an extensive series of tests on three-electrode electrostatic lenses, as a function of geometrical and voltage parameters. Our studies enabled us to select optimum designs for the lenses in the electron microscope. We early on discovered that, in general, electron lenses are not “thin” lenses, and that aberrations of focal point and aberrations of focal length are not the same. I found electron optics to be an intriguing blend of theory and experiment. A laboratory version of the electron microscope was built and tested, and a report was given at the December 1947 EMSA meeting. The micrograph in fig. 1 is one of several which were presented at the meeting. This micrograph also appeared on the cover of the January 1949 issue of Journal of Applied Physics. These were exciting times in electron microscopy; it seemed that almost everything that happened was new. Our opportunities to publish were limited to patents because Mr. Farrand envisaged a commercial instrument. Regrettably, a commercial version of our laboratory microscope was not produced.
Extension of the “thin-crystal” condition by small crystal tilts: Why HREM images of SiC polytypes always look tilted
Authors: O'Keefe Michael A. , Radmilovic Velimir 
Published: June 2020

Both experimental and simulated high-resolution electron microscope images of silicon carbide polytypes commonly exhibit symmetry changes in thicker crystal regions compared to the perfect (projected) space group symmetry of images from thin crystals. However, the changes predicted by simulation, and those found experimentally, are quite different.High-resolution transmission electron microscope images of silicon carbide polytypes were obtained with the JEOL ARM-1000 high-resolution electron microscope in the course of an investigation into a series of metal matrix composites. Like all HRTEM images of silicon carbide, these images failed to show the correct symmetry in the thicker parts of the specimen. Changes in image symmetry as crystal thickness is increased also occur when images of silicon carbide are simulated; for example, Smith and O'Keefe simulated images of polytypes of silicon carbide for crystals oriented so that the electron beam was precisely along the <1210> direction, and found marked departure from thin-crystal symmetry at thicknesses of the order of 150Å for an electron energy of 500keV. However, the lack of symmetry in their simulated images appears to be due to the presence of many second-order terms contributing to the intensity spectra of the thick-crystal images, whereas the symmetry changes in experimental images from thicker crystals are usually of the form that preserves the thin-crystal-like contrast for one set of “twin” spots, yet smears out the contrast of the other. A typical example of this latter effect can be seen in the image of the 6H variant of SiC shown in figure 1.
Interpreting HVEM of muscle-cell impulse networks
Authors: DeCosta Paul , Cho Kyugon , Shemlon Stephen , Jun Heesung , Dunn Stanley M. 
Published: June 2020

Introduction: The analysis and interpretation of electron micrographs of cells and tissues, often requires the accurate extraction of structural networks, which either provide immediate 2D or 3D information, or from which the desired information can be inferred. The images of these structures contain lines and/or curves whose orientation, lengths, and intersections characterize the overall network.Some examples exist of studies that have been done in the analysis of networks of natural structures. In, Sebok and Roemer determine the complexity of nerve structures in an EM formed slide. Here the number of nodes that exist in the image describes how dense nerve fibers are in a particular region of the skin. Hildith proposes a network structural analysis algorithm for the automatic classification of chromosome spreads (type, relative size and orientation).
Evidence for helical structures in poly(l-olefin sulfones) by TEM
Authors: Ruben George C. , Stockmayer W.H. 
Published: June 2020

Advances in the techniques of TEM, including the preparation of ultrathin vertically shadowed platinum-carbon (Pt-C) replicas, have allowed the direct recognition of single-structural features, such as DNA , pectin helices or polysiloxane polymers. Here we report some observations on the chain conformations of serval poly (olefin sulfones). We find strong evidence for the presence of some helical conformations, which had been inferred for over a decade but could not so far be established by other methods.Unusual conformational behavior of poly(olefin sulfones) was indicated over twenty-five years ago. Dilute solutions of several poly (1-olefin sulfones), [-CH2-CHR-S02-]X, in non-polar solvents exhibited unexpectedly strong low-frequency dielectric dispersion, with relaxation times typical of rigid tumbling or of the terminal normal mode. In contrast, polysulfones made from olefins with internal double bonds show no low-frequency dielectric loss. To explain these facts, we refer to the crucial experiments of Fawcett and Fee (1982), who prepared terpolymers of 1-hexene,
Immuno-electron microscopy at sub-nanometer resolution
Authors: Steven Alasdair C. , Newcomb William W. , Booy Frank P. , Brown Jay C. , Trus Benes L. 
Published: June 2020

We have been studying the structure and assembly properties of the capsid of herpes simplex virus, type 1 (HSV-1), whose icosahedral shell (T=16) is ∽ 125 nm in diameter, has a mass of ∽ 200 MDa, and is composed of at least six protein species, ranging from 12 kDa to 149 kDa per monomer. To this end, the structures of empty and full purified capsids have been visualized in three-dimensional reconstructions from cryo-electron micrographs, at a resolution of ∽ 3.5 nm. With the intent of identifying specific structural features of the capsid in terms of particular proteins, or particular segments of these proteins, we have begun to explore the potentialities of cryo-reconstructions of capsids decorated with monoclonal antibodies.B-capsids were purified from BHK cells infected with the MP strain of HSV-1. Some material was analyzed directly by cryo-electron microscopy and image reconstruction as described. Other samples were incubated with approximately equimolar amounts of a monoclonal antibody (8F5) raised against purified VP5 (the major capsid protein, 149 kDa). The resulting precipitate was then washed with buffer to flush out unbound antibodies, and then analyzed in the same way, i.e. by observation in a Philips EM400T equipped with a Gatan 626 cryo-holder. The specificity of Mab.8F5 for VP5 was confirmed by an ELISA with purified VP5.
Distribution and function of non-histone proteins in human chromosomes
Authors: Earnshaw W.C. , Cooke C.A. 
Published: June 2020

The role of non-histone proteins in the structure and movements of mitotic chromosomes remains poorly understood. We describe here experiments aimed at characterization of the distribution of two very different classes of these proteins. The first is composed of integral components of the centromere (or primary constriction). The second class consists of proteins that we have termed “chromosome passenger proteins”. These proteins are chromosomal during most of the cell cycle, but appear to be associated with the cytoskeleton during anaphase and telophase.The centromere regions of chromosomes perform three essential functions in mitosis. (1) They form the site of attachment of the chromosomes to the mitotic spindle. (2) They contain the mechanochemical motor molecules that are responsible for the movements of the chromosomes along microtubules. (3) They regulate the pairing of sister chromatids during mitosis. The first two of these mitotic functions are properties of a disk-shaped structural specialization, the kinetochore, which is located at the surface of the centromeric heterochromatin.
The effect of cytoskeletal protein mutations on cell motility and morphogenesis
Authors: Knecht David A. 
Published: June 2020

The cortical cytoskeleton of eukaryotic cells is composed of actin filaments and a variety of associated proteins. The polymerization, depolymerization, cross-linking and bundling of these filaments, are presumed to be intimately involved in such processes as cell motility, cell adhesion and cell shape. In developing systems, all of these processes are involved in the morphogenetic mechanisms that shape tissues, organs and organisms.We are investigating the complex interactions among cytoskeletal proteins using the simple eukaryotic amoebae, Dictyostelium discoideum. Our approach is to determine the function of the components of the cytoskeleton by creating mutants lacking particular proteins, or containing specific alterations in these proteins. Mutants lacking myosin heavy chain have been created using antisense RNA and homologous gene targetting. These cells have alterations in their shape and movement, and are incapable of accomplishing normal morphogenesis. Another cytoskeletal protein is ABP-120, which is capable of cross-linking actin filaments into orthogonal arrays, leading to the formation of an actin gel in vitro. ABP-120 is found in newly formed pseudopods extended during the chemotactic respose to extracellular cAMP. Mutants lacking this protein have been created by disruption of the chromosomal gene with a transformation vector. These cells are not as dramatically affected as the myosin mutants, but have clear alterations in their motility and in the pathway of responses in the cytoskeleton that correlate with the expected function of this protein. Mutations in several other cytoskeletal genes are currently being constructed.
In situ hybridization detection of gene expression for hepatic metabolic enzymes
Authors: Cardell Robert R. , Davis Betty B. , Drake Richard L. 
Published: June 2020

Key enzymes involved in gluconeogenesis and glycolysis are uniquely distributed within the liver lobule as shown, for example, by periportal hepatocytes having higher activities and quantities of the former and pericentral cells having higher activities and quantities of the latter enzymes. In this report we describe changes in the patterns of mRNA for a key gluconeogenic enzyme, phosphoenolpyruvate carboxykinase (PEPCK), in normal rats and diabetic rats with/without insulin treatment.A 1.0 kb cDNA for rat PEPCK was subcloned into pGEM-3Z. 32P-labeled antisense and sense (control) RNA probes were produced and used for Northern blot analysis which showed that the antisense probe recognized a 2.8 kb mRNA in rat liver which corresponds to the PEPCK mRNA. The sense probe showed no affinity for mRNA from rat liver, lung or colon. 35S-labeIed antisense and sense RNA probes were prepared for in situ hybridization. These were degraded to an average length of 100-200 bases by alkaline hydrolysis. Six to 10 μm paraffin and frozen sections of rat liver were mounted on Tespa treated slides and were post-fixed in 4% paraformaldehyde in PBS for 20 min, treated with 20 μg/ml proteinase K, and further fixed in 4% paraformaldehyde. The sections were treated with acetic anhydride, dehydrated and air dried prior to hybridization. The 35S-UTP labeled RNA probes were dissolved at a final concentration of 1.0 x 105 cpm/μl in a hybridization solution with 50% formamide and used to hybridize each section at 55°C overnight under glass cloverslips. The slides were washed at a high stringency and treated with RNase A. After rinsing, the slides were dehydrated and air dried before autoradiography using Ilford K5 nuclear track emulsion. Some sections were stained in 0.02% toluidine blue and others were mounted unstained for image analysis.
HREM of superstructures in high-temperature superconductors
Authors: Marks L. D. , Tsurata C. , Theil J. , Poeppelmieir K. 
Published: June 2020

Fairly substantial interest has been aroused recently in the new wave of high temperature superconductors. The first such material discovered, La1.83Sr.17CuO4, has been reported to have a body centered tetragonal structure with a=b=.38 nm and an elongated c=1.3 nm. we have used HREM and electron diffraction on a new Hitachi H-9000 microscope at Northwestern (Cs=.9 mm, 300 kV) to analyse the structure of this material. In addition to phases which correspond to the reported structure, we have also observed phases with rather clear superstructures which correspond to a quadrupling of the unit cell, for instance Figures 1 and 2.An additional point of interest is that the material showed no indication of losing oxygen by DIET processes, despite observation of the same crystal for more than 10 hrs.