bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron Cytochemical Study of Corneal Epithelial Repair After Carbon Dioxide Laser Damage
Authors: Tsou K. C. , Severdia J. , Stuck B. , Beatrice E.
Published: June 2020

Investigation of laser damage to the eye relies mainly on electron microscopy because of the limitation of the amount of tissue available for such study and the low level of damage that is discernible only under the electron microscope (1). Previously, we showed that functional damage to Rhesus monkey cornea epithelium by carbon dioxide laser could be studied with cytochemical methods adaptable to electron microscopy (2). The present paper reports repair of corneal epithelium in Rhesus monkey, following treatment by carbon dioxide laser.

Rhesus monkey corneas were divided into three sections: the damaged area in the center (Area 1), the adjacent area (Area 2), and the area next to the sclera region (Area 3). The tissues were fixed in 3% glutaraldehyde in 0.25 M sucrose overnight for NADH diaphorase (2) and Mg++-ATPase (3) study, and postosmicated with 1% Os04in cacodylate buffer. Lasing effect could not be seen visually after 24 hrs.
Ultrastructural Aspects of Ependymal Cells Covering the Feline Area Postrema
Authors: Klara P.M. , Brizzee K.R.
Published: June 2020

Recent ultrastructural examination of the feline area postrema (AP) demonstrated that the ependyma that covers this circumventricular organ shows several morphological characteristics that distinguish it from typical mural ependyma. Cat AP ependyma lacks the cilia present on the surface of typical mural ependyma but has numerous microvillar projections. The apical portions of AP ependyma are connected by zonula adherentes while maculae occludentes,which characterize mural ependyma,are not obvious. Subcellular organelles present in AP ependyma include: mitochondria, inclusion bodies, Golgi and endoplasmic reticulum of both rough and smooth varieties. While all of these organelles are normally present in mural ependyma, cat AP ependyma sometimes displays a whorled type array of endoplasmic reticulum.
An Aortitis of Knots Caused by a Besnoitia-Like Agent
Authors: Simpson C. F. , Woodard J. C. , Forrester D. J.
Published: June 2020

An epizootic among knots (Calidrus canutus)on the Gulf coast of Florida was characterized by considerable mortality. From a histologic study of birds that died, it was concluded that the etiologic agent of the disease was an encysted sporozoan parasite closely associated with the endothelium of the thoracic aorta. The parasitized aortas were examined with the electron microscope in order to characterize the agent involved.

In 1 μm sections of plastic embedded artery examined with the light microscope, it was observed that the etiologic agent was a multinucleated cyst which was closely associated with, or attached to, the luminal aspect of the aorta. The cyst consisted of four layers (Fig. 1). The most internal layer was a central area of vacuolization which contained a round body. The second most peripheral layer contained several nuclei.
Scanning and Transmission Electron Microscopy of the Endometrium in Women with Ovarian Dysgenesis (Turner'S Syndrome)
Authors: González-Angulo A. , Armendares-Sagrera S. , Ruíz de Chávez I. , Marquez-Monter H. , Aznar R.
Published: June 2020

It is a well documented fact that endometrial hyperplasia and adenocarcinoma may develop in women with Turner's syndrome who had received unopposed estrogen treatment (1), as well as in normal women under contraceptive medication with the sequential regime (2). The purpose of the present study was to characterize the possible changes in surface and glandular epithelium in these women who were treated with a sequential regime for a period of between three and eight years. The aim was to find organelle modifications which may lead to the understanding of the biology of an endometrium under exogenous hormone stimulation. Light microscopy examination of endometrial biopsies of nine patients disclosed a proliferative pattern; in two of these, there was focal hyperplasia. With the scanning electron microscope the surface epithelium in all biopsies showed secretory cells with microvilli alternating with non secretory ciliated cells. Regardless of the day of the cycle all biopsies disclosed a large number of secretory cells rich in microvilli (fig.l) with long and slender projections some of which were branching (fig. 2).
Electron Microscopic Studies of Gerbil Testis After Vasectomy
Authors: MAJUMDAR S. K. , KALENSCHER FRED
Published: June 2020

Ultrathin sections made from bilaterally vasectomized as well as bilaterally sham-operated Mongolian gerbils (Meriones unguiculatus) were examined and compared under an electron microscope in order to determine whether vasectomy has any effect upon the fine structure of the testis. The whole testes were removed and placed in Karnovsky's fixative for one hour. After this period the testes were diced into small pieces and fixed for an additional hour in the same fixative. After rinsing in distilled water and postfixed for one hour in OsO4, the tissues were embedded in Epon 812. The sections were stained with uranyl acetate-lead citrate and examined on a Philips Model 201 transmission electron microscope. Shamoperated testis exhibited normal structure of germ cells.
Retinal Fixation Studies on Rat Eyes to be Flown on Russian Satellite #782
Authors: Philpott Delbert E. , Corbett R. , Turnbill C. , Black S.
Published: June 2020

The distribution of the various organs and tissues from a limited number of rats to be flown on Kosmos #782 made it necessary for us to relinquish perfusion which has worked so well in earlier investigations and adapt to another method of tissue fixation. Ultrastructural observations are dependent upon complete and excellent fixation and eyes could only be obtained after decapitation and enucleation. In addition: (1) The entire retina had to be fixed with a minimum loss of tissue, (2) The retina had to survive a prolonged fixation period for collection and return to the USA, (3) The operation had to be as simple as possible for others to perform, and (4) The fixative had to preserve the hard sclera and adjacent soft retinal tissue.
Ultrastructural Alterations in Sinusoidal Endothelial Fenestrae as a Result of Hypoxia
Authors: Nopanitaya Waykin , Brown Raeford E. , Grisham Joe W. , Carson Johnny L.
Published: June 2020

Mammalian endothelial cells lining hepatic sinusoids have been found to be widely fenestrated. Previous SEM studies (1,2) have noted two general size catagories of fenestrations; large fenestrae were distributed randomly while the small type occurred in groups. These investigations also reported that large fenestrae were more numerous and larger in the endothelial cells at the afferent ends of sinusoids or around the portal areas, whereas small fenestrae were more numerous around the centrilobular portion of the hepatic lobule. It has been further suggested that under some physiologic conditions small fenestrae could fuse and subsequently become the large type, but this is, as yet, unproven.

We have used a reproducible experimental model of hypoxia to study the ultrastructural alterations in sinusoidal endothelial fenestrations in order to investigate the origin of occurrence of large fenestrae.
Human Enamel Replication
Authors: Dockum Norman L. , Dockum John G.
Published: June 2020

Ultrastructural characteristics of fractured human enamel and acid-etched enamel were compared using acetate replicas shadowed with platinum and palladium. Shadowed replications of acid-etched surfaces were also obtained by the same method.

Enamel from human teeth has a rod structure within which there are crystals of hydroxyapatite contained within a structureless organic matrix composed of keratin. The rods which run at right angles from the dentino-enamel junction are considered to run in a straight line perpendicular to the perimeter of the enamel, however, in many areas these enamel rods overlap, interlacing and intertwining with one another.
Fine Structure of Planarian Neuroglial Cell
Authors: Morita Michio , Best Jay Boyd
Published: June 2020

The species of the planarian Dugesia dorotocephala was used as the experimental animal to study a neuroglial cell in the ventral nerve cord. Animals were fixed with 3% buffered glutaraldehyde solution and postfixed with 1% buffered osmium tetroxide.

The neuroglial cell is multipolar, expanding into three or four cytoplasmic processes with many daughter branches. Some neuroglial processes are found to extend perpendicular to the longitudinal nerve fibers, whereas others are seen to be parallel to them. The nucleus of the neuroglial cell is irregular in shape and frequently has a deep indentation. Convex portions of the nucleus seem to be related to the areas from which cytoplasmic processes are extended. Granular endoplasmic reticulum (Fig. 4), Golgi body (Fig. 2), mitochondria (Figs. 1 and 2), microtubules (Fig. 4), and many glycogen granules are observable in the electron dense neuroglial cytoplasm. Neuroglial cells are also observed to contain various sizes of phagosomes and lipids (Fig. 2).
Cell Junctions in the Hepatopancreas of the Isopod, Armadillidium Vulgare
Authors: Gonzalez Marcia Vega
Published: June 2020

An ultrastructural study of the hepatopancreas of the terrestrial isopod, Armadillidium vulgare, indicates that morphological change in intercellular membrane apposition parallels functional differention of cells. In the isopod the midgut is structurally and functionally represented by the hepatopancreas. Each of the four lobes of this structure is histologically differentiated into regenerative, transitional and glandular regions, which progress from the distal to the proximal end respectively, and then connect through ducts to the hindgut.

The distribution of cellular organelles is similar in all cells of the regenerative region. Plasma membranes of adjacent cells are separated by a distance of 160 A, (fig. 1). There is no indication of specialized membrane apposition such as junctional complexes or gap junctions. The cell membranes do not exhibit infoldings or extensive convolutions.
Fixation of the Crystalline Style of Bivalve Molluscs (Anodonta Sp.) for Scanning Electron Microscopy
Authors: Ingham E.
Published: June 2020

In the digestive tract of certain bivalves such as oysters and mussels, a structure known as the crystalline style functions as a grinding mechanism for the breakdown of large food particles. The style is located in the posterior portion of the bivalve stomach where it is extruded from the style sac and slowly rotated across the interior of the stomach. It grinds against a hardened portion of the stomach wall known as the gastric shield. The rotation of the style serves to draw the contents of the stomach through this organ, thus taking the place of any musculature that would otherwise be necessary. In several of the species that produce this structure, the style is re-absorbed when the bivalve is not feeding. This has lead to the proposal that the style serves as a nutrient source in starvation condition as well as an organ for maceration. The style is extruded again when food is available, incorporating in its structure the first food particles to enter the stomach.
Visualization of Surface-Associated Nucleic Acid in Tumoricenic Cells Using Ultrathin Frozen Sections and Platinum-Pyrimidine Complexes
Authors: Aggarwal Surinder K.
Published: June 2020

Platinum-pyrimidine complexes have been used as sole electron-dense stains for electron microscopy on number of mammalian cells (1-3) . They are selective for areas rich in nucleic acids and stain the cellular chromatin, ribosomes and nucleolus. Tumorigenic cells exhibit special binding on the plasma membrane surface in the form of dense patches; normal cells do not. Solid tumor biopsy samples from animals and humans show similar patches but only in malignant tissues. Various enzymatic studies suggest that the electron-dense patches are DNA with neuraminic acid involved in the binding. Autoradiographic studies using H3-thymidine confirms the presence of surface- associated DNA.

Swiss Webster mice bearing ascites sarcoma-180 tumor are given intraperitoneal injection of 7. 0 μ c of tritiated thymidine in 0. 5 ml sterile 0. 85% NaCI on day 5 of the tumor implant.
Normal Rat Urinary Bladder: Developmental Variations in Surface Contour
Authors: Malick Linda E.
Published: June 2020

Since rats, hamsters and mice are commonly used for testing potential carcinogens, a study of the normal surface structure of urinary bladder epithelium of different age animals was undertaken to provide a basis of comparison for long term studies of animals with experimentally treated bladders. Scanning electron microscopy (SEM) provides a unique opportunity to rapidly detect and map out altered cell surfaces.

Healthy albino rats from the 17th day of gestation to 7 months of age were anesthetized. The abdominal cavity of each animal was opened and the urinary bladder perfused in situ with 2.5% buffered glutaraldehyde, pH 7.4.
Fenestrations in Normal and Oxidant-Exposed Alveolar Walls in the Lungs of Exercising Squirrel Monkeys.
Authors: Bils Robert F.
Published: June 2020

The significance of the lung alveolar pores of Kohn has been discussed in great detail. Though not proven conclusively, the assumed function of these pores or fenestrations is that of collateral ventilation in the event of airway obstruction (1). Boatman and Martin (2) concluded that the alveolar pores in the dog lung were lined with alveolar epithelium, and that many of the alveolar pores had epithelial junctions on one or both sides of the pores.

Squirrel monkeys were exposed to 0.6 ppm ozone for 4 hours per day for 4 days with intermittent exercise in a rotating cylinder. Following standard procedures for processing the lung tissues for TEM and SEM (3), alveolar walls of exposed and control animal lungs were studied. Pathological lesions were focal and centroacinar involving both the terminal bronchioles and alveoli. Normal alveolar wall fenestrations (Pores of Kohn) were seen in the control tissues, but they were significantly increased in number and size after exposure 4 days consecutively.
Morphometry Evaluation & Ultrastructure of the Lungs of Rats Exposed to Low Levels of Ozone
Authors: Boatman E.S.
Published: June 2020

Ozone (O3) is one of the principal oxidants formed in polluted air. It is a highly reactive gas which readily attacks biological tissues to give rise to a diversity of changes, both marked and subtle. The effects of prolonged exposure to low concentrations of O3 on the function and structure of the lungs is a subject of considerable interest and speculation.

This study is concerned with the functional, structural and morphometric changes in the lungs of rats exposed to 0.45 ppm of 03 for 6 hrs/day, 5 days/ week for up to 10 weeks.

Lungs were fixed at a constant distending pressure of 25 cm of water with 0.1M sodium cacodylate buffered 1.5% glutaraldehyde pH 7.4 for 18 hours, sliced transversely and post fixed in buffered 1.0% osmium tetroxide. Tissue slices from left and right lungs were embedded in epoxy resin, sectioned at l.0μ and stained with azure II methylene blue.
Alteration of Mitochondria in Oxythiamine-Induced, Acute Thiamine Deficiency in the Mouse
Authors: Watanabe Itaru , Scarpelli Dante G.
Published: June 2020

Acute thiamine deficiency was produced in mice by the administration of oxythiamine, a thiamine analogue, superimposed upon a thiamine deficient diet. Adult male Swiss mice (30 gm. B.W.) were fed with a thiamine deficient diet ad libitumand were injected with oxythiamine (170 mg/Kg B.W.) subcutaneously on days 4 and 10. On day 11, severe lassitude and anorexia developed, followed by death within 48 hours. The animals treated daily with subcutaneous injections of thiamine (300 μg/Kg B.W.) from day 11 through 15 were kept alive. Similarly, feeding with a diet containing thiamine (600 μg/Kg B.W./day) from day 9 through 17 reversed the condition. During this time period, no fatal illness occurred in the controls which were pair-fed with a thiamine deficient diet.

The oxythiamine-treated mice showed a significant enlargement of the liver, which weighed approximately 1.5 times as much as that of the pair-fed controls. By light and electron microscopy, the hepatocytes were markedly swollen due to severe fatty change and swelling of the mitochondria.
Gallstone Ultrastructural Analysis
Authors: McConville R.L. , McConville B.E.
Published: June 2020

A detailed knowledge of the structure of gallstones is important since the gallstones contain a record of those changes in the tody which influence the function of the liver and the gallbladder, and since 15-20 million people in the United States alone, suffer from the disease (l), investigations leading to a “better understanding of the disease is a worthwhile endeavour.

A study of one of the most common categories of gallstone is reported here:- a mixed stone of cholesterol and calcium carbonate from a multiple deposit. This was a small (approx. 0.8 cm. diameter) off-white, spherical stone with a heavily pigmented centre. The stone was prepared and analysed using the scanning electron microscope (S.E.M.) together with energy dispersive X-ray analysis in the manner used for urinary calculi (2).
Rapid Chemical Dehydration of Mammalian Tissues for Scanning Electron Microscopy using 2 ,2-Dimethoxypropane
Authors: Maser Morton D , Trimble John J.
Published: June 2020

Muller and Jacks used 2,2-dimethoxypropane (DMP) as a dehydrating agent for biological specimens prior to embedment, ultrathin sectioning, and examination by transmission electron microscopy. Acidified DMP reacts endothermically with water to produce methanol and acetone. Muller and Jacks demonstrated excellent fine structural preservation in a variety of specimens dehydrated with DMP.

We have used the same method, prior to critical point drying, to prepare specimens for scanning electron microscopy (SEM) . Portions of the trachea, small intestine, and kidney from a laboratory mouse killed by cervical dislocation were fixed for 16 hours in cold 3% glutaraldehyde in 0.1 M phosphate buffer, pH 7.2.
Preservation of the Glycocalyx and Mucin Granules by Rapid Dehydration and Embedding
Authors: Hess R. A. , Thurston R. J. , Kilburn K. H.
Published: June 2020

The polysaccharide-containing glycocalyx (1) found on the external surface of cells is difficult to preserve and usually requires special stains for observation with the electron microscope. Ito (2) demonstrated filamentous material lining intestinal microvilli. The bronchiolar epithelium has also been shown to have a mucopolysaccharide layer (250 Å thick) (3). Such structures are considered to be part of the cell membrane, rather than components of mucin produced by the goblet cells (2). This investigation showed that rapid dehydration and embedding preserved mucopolysaccharides and glycoproteins of mucin granules and the glycocalyx for ultrastructural evaluation.
Preparative Techniques for Sem Examination of a Smooth Plastic Fabricated for use as a Blood-Handling Surface
Authors: Kurusz M. , Mumaw V.R. , O'Bannon W. , Donachy J.H. , Pierce W.S.
Published: June 2020

Efforts are underway to develop a left ventricular assist pump and total artificial heart for use in patients with end-stage cardiac disease. The blood-handling material in both devices is a smooth elastomer of the segmented polyurethane family that has excellent mechanical, chemical, and biological properties when used in animal studies. However, a persistent problem with any artificial blood-handling device is activation of the coagulation system and the development of thrombo-emboli.

Scanning electron microscopy was used to evaluate the microtopography of the plastic surfaces for baseline information and to compare the effects of different fabrication techniques upon surface finish prior to implantation of assist devices in bovines. Defining surface smoothness is difficult, but it is believed that thrombo-resistant surfaces must not have any defects larger than the diameter of blood platelets (2-4μm).
UHV In-Situ Electron Microscopy of thin Film Growth
Authors: Yagi K. , Takayanagi K. , Kobayashi K. , Honjo G.
Published: June 2020

An ultra-high vacuum (UHV) electron microscope was constructed for special purpose of in-situ studies of thin film growth and some experimental results have already been published (1). Here, recent results are described.

1. Au/graphite (nucleation and growth mode). Growths of Au in a dendritic shape at 150°C were observed on graphite. The dendritic morphology was said to be characteristic of the Au growth on UHV cleaved graphite (2). We cleaned an air cleaved surface by heating in UHV EM (10-8 torr) for 20 minutes prior to the Au deposition. The dendritic shape growth in Fig. 1, therefore, indicates that the graphite surface became clean with the present heat treatment and that the in-situ studies were done under clean conditions.
Anisotropic Membranes as Substrates for Sem
Authors: Turnbull Thomas P. , Bowers W. F.
Published: June 2020

Until recently the prime purposes of filters have been to produce clear filtrates or to collect particles from solution and then remove the filter medium and examine the particles by transmission electron microscopy. These filters have not had the best characteristics for scanning electron microscopy due to the size of the pores or the surface topography. Advances in polymer chemistry and membrane technology resulted in membranes whose characteristics make them versatile substrates for many scanning electron microscope applications. These polysulphone type membranes are anisotropic, consisting of a very thin (0.1 to 1.5 μm) dense skin of extremely fine, controlled pore texture upon a much thicker (50 to 250μm), spongy layer of the same polymer. Apparent pore diameters can be controlled in the range of 10 to 40 A. The high flow ultrafilters which we are describing have a surface porosity in the range of 15 to 25 angstrom units (0.0015-0.0025μm).
Image Simulation of Dislocation Loops
Authors: Ohr S. M.
Published: June 2020

Computer simulation of image contrast is a useful tool in the identification of lattice defects observed in the electron microscope. In order to obtain high quality simulated micrographs, it is necessary either to consume a considerable amount of computer time or to have the micrographs processed through special photographic devices. In this paper, we describe a numerical scheme by which half-tone simulated images of dislocation loops can be constructed with efficient use of computer time and without special photographic handling.

We have solved the Howie-Whelan two-beam dynamical equations by the extrapolation method of Bulirsch and Stoer which has been shown to be about six times faster than the Runge-Kutta method. The method evaluates the transmitted and diffracted intensities at the bottom surface of the foil as a function of step size. The final solution is obtained by forcing the convergence of this sequence of solutions to the limit.
Dynamic Dark-Field Electron Microscopy
Authors: Haydon G.B. , Crane R.A. , Zercher C.R.
Published: June 2020

Dynamic dark-field electron microscopy as described here provides capabilities not present with other methods. An annular ring of any selected diameter is used to illuminate the specimen. Diffraction rings selected by the objective aperture are integrated photographically to produce the dark-field image.

All methods of dark-field electron microscopy eliminate the incident illumination from the image and utilize only a selected portion of the scattered electrons and each has its limitations (1):

1. Movement of the objective aperture off of the optical axis introduces spherical aberation which increases as the 4th power of the distance from the axis.

2. Tilting the beam either mechanically or electrically allows only those electrons scattered in one direction to be imaged.
Some Observations on the Adsorption of Heavy Atoms on Carbon Substrates
Authors: Isaacson M. S. , Kopf D. , W. Parker N. , Utlaut M.
Published: June 2020

In previous papers we have shown that the use of the atomic resolution STEM to study adsorption of heavy atoms on light element substrates could be of potential value in surface science. We indicated that we had undertaken a program to determine to what extent that was true and that one particular measurement we were attempting was to measure adatom-adatom spacing distributions. In this paper we would like to present some further results and also discuss the general validity of our approach.

At present, our specimens are made by depositing 5 μl of a 10-4 - 10-5 M solution of a heavy-atom-containing molecule onto a thin carbon film. The drop is allowed to sit for about 20 seconds and then pipetted off the film. This results in the heavy atoms being deposited within a molecule and so if the molecule remains intact, the preferential spacings between heavy atoms which may be observed could be dependent upon the molecule.
A Field Emission Probe Forming System with a Magnetic Pre-Accelerator Lens
Authors: Pei Kuo Huei , Siegel Benjamin M.
Published: June 2020

A field emission electron probe forming system with a magnetic preaccelerator lens has been developed.

The magnetic lens has been designed using computer optimization for best compromise between high lens quality, ease of tip manipulation and tolerable power dissipation of the exciting coil. Figure 1 shows the configuration of the magnetic lens and the field emission tip assembly. The optical properties of the magnetic lens are plotted in Figure 2.

The performance of the magnetic pre-accelerator lens was evaluated with a prototype electron optical bench developed by Veneklasen. It consists of a two cylinder accelerator, a magnetic transfer lens and a projector lens followed by a razor blade assembly for measurement of the spot size and the beam current.
Use of Stem Convergent Beam Electron Diffraction Patterns for Foil Thickness Determination
Authors: Rao Prakash
Published: June 2020

A knowledge of the specimen foil thickness to a considerable degree of accuracy is vital to any quantitative microstructural measurement such as dislocation density, precipitate particle number density, or defect cluster number density in irradiated materials. Several techniques have been used in the past with varying degrees of accuracy and success. These include the use of the trace method (with a slip trace, stacking fault or grain boundary), counting extinction contours in a wedge shaped crystal, or stereomicroscopy when there are defects intersecting the foil surface or identifiable material on these surfaces. All of these techniques are seldom accurate to within ±10%. More recently, intensity oscillations observed in convergent beam diffraction patterns have been used to determine foil thicknesses with a considerably greater degree of accuracy.
Electron Metallography Methods Applied to Studies of Recovery and Recrystallization in Rolled Tantalum Single Crystals
Authors: Johnson D. H. , Snyder W. B.
Published: June 2020

Recovery and recrystallization studies of deformed tantalum single crystals show widely varying recrystallization behavior. Image analysis methods, utilized to quantitatively characterize changes, are described; advantages in precision, reproducibility, and operator time were realized over conventional methods. The data obtained compared well with previous data for niobium.

Dislocation densities were measured by placing bright field micrographs in the scanner of an image analyzing microscope; the contrast was adjusted to differentiate the dislocations; and their area fraction (total line length) measured directly. The projected line length, A, of dislocations was corrected to total line length by multiplying by a shape factor. Foil thickness, t, was determined by counting thickness fringes from the edge of the perforated hole.
Aperture Dependence of Resolution and Beam Transmission in High-Voltage Tem of Thick Biological Specimens
Authors: Fotino Mircea
Published: June 2020

In standard transmission electron microscopy the image is formed by electrons scattered both elastically and inelastically within the specimen. Their relative contributions to the image quality are determined by electron energy, specimen thickness and vertex half angle a of the collection cone defined by the objective aperture.

The cross sections for scattering into a given angle decrease as the electron energy increases to the MeV region (1), and the accompanying increased preponderance of the elastic component results in improved resolution in the image of thin objects.

In most biological applications of high-voltage electron microscopy the usual thickness range (0.25-5.0 μn) is such that plural scattering within the specimen becomes the dominant factor for resolution and contrast (e.g.(2)). In particular, increased fractions of electrons are removed from the transmitted beam by scattering outside the collection cone.
Reduction of Specimen Contamination in Electron-Beam Instruments
Authors: Lehmpfuhl G. , Smith P. J.
Published: June 2020

Specimens being observed with electron-beam instruments are subject to contamination, which is due to polymerization of hydrocarbon molecules by the beam. This effect becomes more important as the size of the beam is reduced. In convergent-beam studies with a beam diameter of 100 Å, contamination was observed to grow on samples at very high rates. Within a few seconds needles began forming under the beam on both the top and the underside of the sample, at growth rates of 400-500 Å/s, severely limiting the time available for observation. Such contamination could cause serious difficulty in examining a sample with the new scanning transmission electron microscopes, in which the beam is focused to a few angstroms.

We have been able to reduce the rate of contamination buildup by a combination of methods: placing an anticontamination cold trap in the sample region, preheating the sample before observation, and irradiating the sample with a large beam before observing it with a small beam.
Ratings of New Films for the High-Voltage Electron Microscope and the Radiation Damage Incurred in Taking Typical Biological Electron Micrographs
Authors: Vernon King Murray , Parsons Donald F.
Published: June 2020

Radiation damage to biological specimens being examined in the electron microscope inevitably restricts the amount of information that can be gathered. This problem is especially severe in the high-voltage electron microscope (HVEM), where the relatively low sensitivities of existing photographic materials entail inordinately long exposures to specimens to the beam that cause enhanced radiation damage, in spite of early hopes that this instrument would alleviate the radiation-damage problem.

We have reported studies of the sensitivities and resolutions of commercial and experimental photographic materials for use with 1-MeV electrons. In the present study, we have chosen certain photographic materials as representing typical films used for electron microscopy or as possessing a favorable combination of sensitivity and resolution for biological electron microscopy, and we have followed the course of impairment of image quality as a selected area of a typical specimen is subjected to ever larger radiation doses.
Dislocation Structures in Titanium
Authors: Fujishiro S.
Published: June 2020

Titanium alloys are important materials for aerospace applications in wide temperature ranges, i.e., from cryogenic to elevated temperatures. Since most commercial alloys are used in near alpha phase (h.c.p.) compositions, it is very important to understand the deformation behavior of Ti at those temperature ranges. In particular, in recent years, the critical resolved shear stresses in major slip systems such as basal, prismatic and pyramidal planes have been one of the most crucial topics in titanium metallurgy. Furthermore, the existence and abundance of dislocations with the c + a Burgers vector in the latter two slip systems became controversial and of great interest for engineers who process the alloys for hardware products. Proving the existence of such dislocations requires very elaborate procedures in which one should establish a two beam condition on two independent planes, both of which belong to the <1123> zone axis, and also observe if the dislocation contrasts disappear on those two planes but not on the rest of the planes which do not contain the same zone axis.
Climb and Glide Dislocation Sources in Quenched Aluminum Alloys
Authors: Westmacott K. H.
Published: June 2020

Concentric dislocation loops are observed frequently in slowly quenched aluminum alloys (for a review see 1). In Al-Cu alloys containing Si as an impurity the loops are found to lie in ﹛1ll﹜ planes in configurations that have been inferred to arise from the operation of Frank-Read glide sources. On the other hand, in Al-Mg and Al-Si alloys detailed analysis has shown that the loops form by dislocation climb in the manner proposed by Bardeen and Herring. Recent work has shown that all multiple loop configurations in Al and its alloys have a common origin, and result from dislocation nucleation and/or vacancy condensation in the vicinity of inclusion particles (2). These processes occur to relieve the large compressive strains which are generated in the lattice around the misfitting particle.
Transmission Electron Microscopy Studies of Crystal Lattice Growth in Atomic Resolution
Authors: Hashimoto H. , Kumaol A. , Ono A. , Watanabe E. , Endoh E.
Published: June 2020

The present authors showed that the image of single atoms in Th-pyromellitate molecules and Th02 small crystals supported on graphite films could be observed in the dark field transmission electron microscopic images with tilted illumination (TDF image). The achievement of the observation of single atoms can be attributed not only to the high contrast of the dark field image but also to the two times higher resolution of the TDF image than that of the bright field image with axial illumination.

Using the TDF image method, the growth process of small ThO2 crystals formed by the electron irradiation in the vacuum has been studied.

Th - pyromellitate of 10-4 mol which was placed on graphite flakes was observed by JEM 100-C electron microscope with an objective lens of spherical aberration coefficient Cs = 0. 7 mm. Objective aperture and illumination tilt angles were 9 x 10-3 rad and 16 x 10-3 rad respectively .
Preliminary Observations of Electron Irradiation Damage in Short-Range Ordered Ni4Mo
Authors: Sinclair R. , Gelles D. S. , Thomas G.
Published: June 2020

Short-range order (SRO) in a solid solution is an inherently stable state. It is a highly localised phenomenon, with atomic correlations rarely extending more than a few unit cells and which is difficult to study and interpret by conventional methods. It has been invoked as one of the possible causes of low swelling rates during irradiation of specific alloys. This idea is currently gaining some foundation especially as swelling has been found to be low in Cu 15%A1 and Ni4Mo, both of which are well-known SRO alloys.

The present experiments are aimed at evaluating the behaviour of SRO Ni4Mo (produced by quenching from above the critical ordering temperature) in an irradiation environment. For this purpose, thin foils, prepared by electropolishing 3mm. discs in dilute H2S04 at room temperature, were examined in a JEOL high voltage electron microscope operating at lMeV (i.e. above the threshold displacement energy for both Ni and Mo).
Identification of Minerals by Electron Diffraction
Authors: Lally J. S. , Lee R. J. , Szirmae A.
Published: June 2020

The employment of electron microscopy to monitor the concentration of particles in air and water samples is now an established method in environmental research. A large amount of effort has been expended on improving methods of specimen preparation and particle counting techniques; however, identification procedures using electron diffraction have not been developed to the same extent. Often, identifications are based on visual assessment of what is loosely called "a characteristic diffraction pattern." This may be an acceptable method when the mineral phases to be identified come from a known source (such as a chrysotile asbestos operation) but are not generally useful when minerals in air and water might come from a variety of sources. The methods to be described here have evolved from the normal identification procedures using standard stereograms of minerals (which is perfectly adequate provided not more than 3 or 4 possible structures are to be tested) into a systematic computer search of large numbers of different crystal structures as possible solutions to a given diffraction pattern.
Void-Lattice Formation in Natural Fluorite by Electron Irradiation
Authors: Murr L.E.
Published: June 2020

The production of void lattices in metals as a result of displacement damage associated with high energy and heavy ion bombardment is now well documented. More recently, Murr has shown that a void lattice can be developed in natural (colored) fluorites observed in the transmission electron microscope. These were the first observations of a void lattice in an irradiated nonmetal, and the first, direct observations of color-center aggregates. Clinard, et al. have also recently observed a void lattice (described as a high density of aligned "pores") in neutron irradiated Al2O3 and Y2O3. In this latter work, itwas pointed out that in order that a cavity be formed,a near-stoichiometric ratio of cation and anion vacancies must aggregate. It was reasoned that two other alternatives to explain the pores were cation metal colloids and highpressure anion gas bubbles.

Evans has proposed that void lattices result from the presence of a pre-existing impurity lattice, and predicted that the formation of a void lattice should restrict swelling in irradiated materials because it represents a state of saturation.
Identification of Faults in Asbestos Minerals and Application to Pollution Studies
Authors: Seshan K. , Wenk H.-R.
Published: June 2020

Asbestos fibre texture occurs in various mineral groups (e.g. chrysotile, crocidolite, tremolite, grunerite, tourmaline) and it has been established that at least chrysotile is carcinogenic. We are investigating various aspects of the asbestos structure, with transmission electron microscopy (TEM) (1) in order to develop methods for unequivocal asbestos identification using minute samples and also to determine defects responsible for the fibre structure in these minerals which often occur as large, we 11-developed single crystals.

In order to do this, we have started by investigating clinoamphibole asbestos such as tremolite Ca2Mg5[Si8O22] (OH, F)2 and crocidolite Na2 (Mg, Al, Fe3+, Fe2+) (Si8O22) (OH, F )2 , from California localities. In crocidoli te - asbestos we observed a high density of very narrow microtwins parallel to the fibre axis [001] (Fig. 1). They are often only 50-100Å wide. Diffraction patterns display the typical twin arrangement of spots and although preliminary contrast experiments are not yet conclusive the twin plane appears to be (100).
Structure of Al-Hf Films
Authors: Smith P. J. , Howard J. K. , Chu W. K. , Lever R. F.
Published: June 2020

The structure of Al-Hf thin films, before and after annealing, has been studied by transmission electron microscopy. A 7000-Å layer of aluminum was evaporated, at a pressure of 5 x 10-7 Torr, onto a silicon wafer that had 5000 Å of thermal SiO2 on top. Onto the aluminum layer, with no break in the vacuum, a 1700-Å. layer of hafnium and then a 1000-Å layer of aluminum were deposited. The resulting three-layer structure was used to determine how different atomic ratios of Al and Hf influence the phases formed.

After 4 hr of annealing at 400 C in a dry nitrogen atmosphere, the upper part of the film was found to be composed of grains of Al3Hf (ZrAl3-type), about 700 Å in diameter (Fig. 1). The reaction appeared to be complete in the upper layer; none of the relatively large Al grains, 2000 Å in diameter, that had been present in the as-deposited sample were found.
A Study of Gaseous and Organic Inclusions in Copper Electrodeposit by Transmission Electron Microscopy
Authors: Nakahara S. , Staudinger A.
Published: June 2020

It was recently shown(1)that gaseous and organic inclusions in electrodeposits can he detected "by transmission electron microscopy (TEM) using a through-focus imaging technique. In this study, we have investigated the sites for incorporation of inclusions and their spacial distribution in copper electrodeposit by TEM.

A copper film was electrodeposited on an annealed OFHC copper sheet in a sulfate electrolyte (200 g/l CuSo4-5H2O, 50 g/l H2So4) containing 5 M Mol./l O-phenanthroline as an organic additive. Plating was carried out at room temperature and at a current density of 5 MA/cm2.

In order to detect gaseous and organic inclusions, all copper deposits were examined in overfocussed as well as underfocussed conditions. In each case, stereo-pairs(2)were obtained. Figures 1 and 2 show stereo-pairs of the deposited copper film taken in overfocussed and underfocussed conditions, respectively.
Acid Phosphatase Localization During Wound Healing in the Rabbit Lens
Authors: Unakar N.J. , Binder L.I. , Reddan J.R. , Harding C.V.
Published: June 2020

Some of the changes that precede the initiation of cell division in the injured and cultured lens have been reported. Studies from other laboratories indicate that acid phosphatase may play a key role in tissue repair. The ocular lens provides a unique system to study this phenomenon in an avascular tissue. Histochemical studies at the level of the light microscope indicate the presence of acid phosphatase which is primarily confined to the peripheral region of the rabbit lens epithelium. However, no information regarding the localization of acid phosphatase in mechanically injured rabbit lenses is available. This investigation was undertaken to ascertain the presence and localization of acid phosphatase following mechanical injury to the central anterior region of the lens.
Mineral Localization During Bone Formation: Secondary Ion and Electron Probe Microanalyses
Authors: Tousimis A. J.
Published: June 2020

Normal mammalian mineralization process results in the formation of hydroxyapatite crystallites and with their subsequent incorporation in the bone matrix. This very important biological phenomenon has attracted the attention of investigators from many disciplines and has been the subject of numerous studies during the past century. The initial stages of bone formation can be observed at the epiphyseal plate. This avascular tissue consists of specialized cells (chondrocytes) which originate at the epiphysis (upper part of schematic Fig. 1) and align themselves in columns filling the thickness of the plate. The chondrocytes secrete the major components of their surrounding matrix which keeps them in relatively straight rows from the epiphyseal to the diaphyseal regions. The epiphyseal is arbitrarily, divided into proliferation, maturation, and mineralization (capillary infiltration level) zones.
Mitochondrial Granules and Dehiscence of the Intercalated Disc in Cobalt Cardiomyopathy
Authors: Sekhri K.K. , Alexander C.S. , Nagasawa H J. , Derr R.F.
Published: June 2020

It is now well established that cobalt was the primary etiologic agent in the “Beer Drinkers” cardiomyopathy which assumed epidemic proportions in recent years. The authors previously reported certain significant ultrastructural alterations in the liver and heart of cobalt treated rabbits. The present report confirms as well as extends the earlier findings on this subject.

Ten rabbits were administered subcutaneously with a daily dose of 2.5 to 25 mg/kg of cobaltous chloride for 11-13 days. The control group of six rabbits received an equivalent dose of 2. 2% sodium chloride solution. The treated rabbits lost about 20% of their body weight and on sacrificing revealed flabby hearts, frequently with pericardial edema.
Steel Knive Sectioning of Epon Blocks as Applied to the Study of Muscle
Authors: Davidowitz Jacob , Pachter Bruce , Brady Gloria , Breinin Goodwin M.
Published: June 2020

Fully cured epon blocks are readily sectioned at 20 to 40 microns by ordinary steel knife on a sliding microtome. Groups of ten or more serial sections may be conveniently mounted on a polystyrene slide with a thin layer of epon cured onto the section surfaces. This serves both to stabilize and clear the sections for light microscopy. The sections are sandwiched between the slide and polished polyethylene during the epon curing, after which the polyethylene peels off leaving the sections adhering to the slide. Without such stabilization, the sections tend to warp with time. Single sections may be freed from the slide and cemented onto support blocks for further sectioning by ultramicrotome.
Chronic Laser Exposure Effects on Rabbit Retina
Authors: Silver Burton B. , Lawwill Theodore
Published: June 2020

Dutch-belted 1 to 2.5 kg anesthetized rabbits were exposed to either xenon or argon laser light administered in a broad band, designed to cover large areas of the retina. For laser exposure, the pupil was dilated with atropine sulfate 1% and pheny lephrine 10%. All of the laser generated power was within a band centered at 5145.0 Anstroms. Established threshold for 4 hour exposures to laser irradiation are in the order of 25-35 microwatts/cm2. Animals examined for ultrastructural changes received 4 hour threshold doses. These animals exhibited ERG, opthalmascopic, and histological changes consistent with threshold damage.

One month following exposure the rabbits were killed with pentobarbitol. The eyes were immediately enucleated and dissected while bathed in 3% phosphate buffered gluteraldehyde.
Cytoplasmic Organization in the Receptor Cells of the Crista Ampullaris
Authors: Dunn Robert F.
Published: June 2020

Receptor cells of the cristae in the vestibular labyrinth of the bullfrog, Rana catesbiana, show a high degree of morphological organization. Four specialized regions may be distinguished: the apical region, the supranuclear region, the paranuclear region, and the basilar region.

The apical region includes a single kinocilium, approximately 40 stereocilia, and many small microvilli all projecting from the apical cell surface into the lumen of the ampulla. A cuticular plate, located at the base of the stereocilia, contains filamentous attachments of the stereocilia, and has the general appearance of a homogeneous aggregation of fine particles (Fig. 1). An accumulation of mitochondria is located within the cytoplasm basal to the cuticular plate.
Regression of Sarcoma-180 after cis-Dichlorodiammineplatinum (II) : A Fine Structural Study
Authors: Sodhi Ajit
Published: June 2020

Sarcoma-180, a transplantable tumor in Swiss White mice regresses completely after a single intraperitoneal injection of cis-Dichlorodiammineplatinum (II). Fine structural studies before and after cis (Pt (NH3)2C12) treatment show certain morphological changes indicative of possible mechanisms involved in the tumor regression. The mitotic activity of tumor cells is inhibited soon after platinum injection possibly due to its interaction with DNA. Appearance of plasma cells (Fig. 1) and lymphocytes within the tumor mass after a 4-6 days period of platinum treatment indicates a possible enhancement of the immune system. The plasma cells display a well developed RER and a typical nuclear morphology. Further studies on spleen of both treated and control animals show an increase in the number of plasma cells after about 5 days of platinum treatment (Fig. 2).

The increase in the lymphocytes and the plasma cells indicates an immune system at the cellular level as these antibody producing cells directly come in contact with the Sarcoma-180 cells. Also the double diffusion method on agar plates indicates the enhanced humoral antibody production against Sarcoma-180 as opposed to the controls.