bluuebunny/crossref_metadata_2025 huggingface dataset:
Light and ultrastructural studies of renin granules in methacrylate and epon embedded kidneys
Authors: Tausch J.H. , Moore J.D. , Barsoum N.J. , Gough A.W. , Sturgess J.M.
Published: June 2020

The juxtaglomerular apparatus (JGA) is a distinct morphofunctional unit in the kidney and the main constituent cells are modified smooth muscle cells called juxtaglomerular (JG) cells. JG cells, located within the sleeve of afferent arterioles of glomeruli, are characterized morphologically by secretory granules. The granules contain renin, an enzyme of the reninangiotensin-aldosterone system that regulates blood pressure and electrolyte balance. The purpose of this report is to describe plastic embedding and staining procedures used to study renin granules by light and electron microscopy in a rat experimental model.

The rats were orally administered enzyme inhibitors that induced hypertrophy and hyperplasia of JG cells resulting in increased storage and synthesis of renin granules. At necropsy, thin transectional slices of renal cortex were collected and specimens for light and ultrastructural examination were taken from adjacent cortical tissue in each rat. For histology, 2 mm thick slices of kidney were fixed in neutral buffered formalin.
Stannous fluoride treatment of acid-etched caries-like lesions of enamel: A scanning electron microscopic study
Authors: John Hicks M. , Silverstone Leon M. , Gantt David G. , Flaitz Catherine M.
Published: June 2020

Although fluoride levels become elevated in sound enamel following a topical fluoride treatment, the caries-preventive effect of fluoride is thought to be due primarily to the role of fluoride in remineralization of clinically undetectable enamel lesions and hypomineralized enamel. During lesion formation, redistribution of fluoride from the enamel surface to the subsurface demineralized enamel occurs. This results in a surface zone with a relatively low fluoride content. In order to maintain an intact surface zone over a carious lesion, it may be necessary to replenish the fluoride levels with an exogenous fluoride source. By acid-etching the lesion surface, a more reactive surface is made available for fluoride interaction. In addition, porosities and etching patterns may be created, allowing for bonding of a caries-resistant resin material to the lesion surface. The purpose of this study was to determine the integrity of the caries-like lesion surface following acid-etching and subsequent stannous fluoride treatment (SnF2).
Morphometric analysis of the effects of phosphorus and chromium on a diatom
Authors: Lazinsky Diane , Sicko-Goad Linda
Published: June 2020

Nutrients, particularly phosphorus, may influence, and in some cases, mediate toxicity effects of heavy metals on algae. Further, heavy metal and phosphorus uptake can be coupled and the metal may be incorporated into polyphosphate bodies thereby reducing the amount of metal available to intracellular sites. A series of experiments was designed to evaluate the effects of chromium on a diatom and to determine if these effects are modified by the phosphorus status of the cell.

A cultured diatom, Cyclotella aff. meneghiniana was the test organism and was grown in WC medium at 20°C. The experimental regime consisted of control cells with the following phosphorus status: phosphorus deficient, phosphorus sufficient, and an overplus of phosphorus which was achieved by placing cells in phosphate free medium and then adding double the standard amount of phosphorus. Hexavalent chromium at a concentration of 0.2 μg-at/L was added to each of the above phosphorus categories. The addition of chromium to the overplus cells occurred before overplus and following the period of overplus.
Observation of Oxidation and Reduction Process of Nb Oxides at Atomic Level Resolution
Authors: Iijima Sumio
Published: June 2020

By using a high resolution electron microscopy we studied planar, linear and point defects occurring in some oxides, particularly Nb and its ternary oxides. In those studies, the image formation of the crystal defects is based on the phase contrast and is different from that of the conventional method (using the diffraction contrast). The electron micrographs of crystals taken under some strict imaging conditions showed roughly distributions of electrostatic potentials in the crystals and the positions of individual metal atoms were resolved. Justification of this intuitive interpretation of the image contrast is provided under some conditions by theoretical calculation of the image using a weak phase object approximation.
High Resolution Scanning Microscopy—What Next?
Authors: Crewe A. V.
Published: June 2020

The current status of high resolution scanning microscopy is probably well enough known that it needs little elaboration. Perhaps it is sufficient to say that resolving power can be achieved which is equal to that of the conventional microscope, that contrast is very high, and that a variety of forms of contrast are available which make use of both elastic and inelastically scattered electrons. The one weakness of the scanning microscope of which we are aware is that it is not as efficient as the conventional microscope for phase contrast or obtaining diffraction information.
Lattice Imaging of Spinodal Alloys
Authors: Gronsky R. , Okada M. , Sinclair R. , Thomas G.
Published: June 2020

Spinodal decomposition in alloys has previously been studied1 by x-ray diffraction and conventional T.E.M., techniques which are used to reveal the wavelengths of the early stage composition modulations through diffracted intensities averaged over a large specimen area. The present paper describes recent progress on DIRECT detection by the lattice imaging technique of the localized variations in lattice parameter characteristic of spinodal decomposition. As in previous studies of ordered alloys this application of lattice imaging avoids the necessity of interpreting severe fringe distortions associated with lattice defects.
Electron-Metallographic Identification of Retained Austenite in Steels
Authors: Narasimha Rao B. V. , Koo J. Y. , Thomas G.
Published: June 2020

Recently it has been discovered by electron microscopy that even in medium carbon steels (Mf≳200°C) small quantities of interlath retained austenite (γ) is present in as-quenched structures. It is speculated that this small quantity of retained γ can have a profound influence on the mechanical properties of steel. This austenite is severely deformed and in most cases the amount is so small that detection by x-ray analysis becomes impossible. However, sophisticated electron microscopic techniques involving careful selected area diffraction, bright field and dark field imaging can unequivocally establish the presence of such small quantities of austentite. Extremely useful morphological and microstructural information on the austenite can also be obtained from the electron metallography.
Examination of Fracture Interfaces in Silicon Nitride
Authors: Tighe Nancy J.
Published: June 2020

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.
Electron Microscope Study of the Effect of Substrate Metal Dislocation Structure on the Structure of Electrodeposited Nickel
Authors: Gundiler I. , Murr L.E.
Published: June 2020

The role of dislocations on crystal growth was first introduced by Frank and an extensive treatment of the theory was developed by Burton, et al. The growth parameters pertaining to electro-crystallization have been defined, and theories on the mechanism and kinetics of electrodeposition have been developed. The formation of spirals and pyramidal growth patterns are both explained by the screw-dislocation mechanism. Two dimensional nucleation on displacement-free surfaces and step-bunching mechanisms have also been suggested.

Although a surface-diffusion-to-dislocation-steps mechanism for electrocrystallization is generally accepted, the effect of dislocation structure and density in the substrate on the microstructure of electrodeposited metals has not been systematically studied.
Clustering and Fluctuation Characteristics of Carbon Films Observed in Darkfield Electron Microscopy
Authors: Brakenhoff G. J.
Published: June 2020

It is possible to determine in darkfield EM the relative mass of, for instance, biological particles. The method is based on the linear relationships, first in darkfield EM between mass and the electron intensity scattered by it, and second between electron intensity and the photographic density in the micrograph. Limitations are set by the background structure present in thin carbon supporting films. Although films without structure (i.e. graphite lamellae, 2)) could be used, this seems not practicable for day to day biological application, hence this investigation of the more common carbon films.

The darkfield mass determination method was modified to obtain particle mass distributions by computer. The micrographs are scanned by a densitometer on a network of (in this case) 50x50μm measuring grid and the density values are put on magnetic tape.
Studies of the Adsorption and Diffusion of Single Heavy Atoms on Light Element Substrates Using the STEM
Authors: Parker N. W. , Isaacson M. , Langmore J. P.
Published: June 2020

Recent advances in dark field high resolution transmission electron microscopy have made possible the observation of individual atoms on thin sub-strates of low atomic number, e.g., Refs. 1-5. Studies at atomic resolution of high atomic number adatoms chemisorbed to low atomic number substrates could be of potential value in obtaining an improved understanding of surface catalysis, chemisorption, characterization of surface structure and the earliest stages of thin film nucleation and growth.
Factors Affecting Practical Performance of the STEM at High Voltages
Authors: Strojnik A.
Published: June 2020

In addition to limited electron source brightness, lens aberrations and the diffraction limitation, which, taken together, represent a fundamental limit of the point-to-point resolving power of a STEM at voltages above 100 k V (at low voltages the use of the field emission gun simplifies the situation somewhat), there are a number of instrumental and/or operational defficiencies that contribute to the gap between the theoretical and practical performance. In fixed beam instruments, operating at up to 100 kV the practical resolution equals the theoretically expected resolving power for suitable specimens. At higher voltages this is not true anymore, mainly due to (i) mechanical instabilities, (ii) electrical instabilities, and (iii) larger aberration coefficients of objective lenses. Exposure times being almost two orders of magnitude longer in the STEM than in TEM at HV, the requirements concerning the electrical and mechanical stabilities become even more severe for STEM.
Reflection Electron Microscopy
Authors: Højlund Nielsen P. E. , Cowley J. M.
Published: June 2020

Reflection electron microscopy was widely used before 1960 for the study of surfaces. For the imaging diffuse scattered electrons was applied. For avoiding a severe foreshortening the surface was illuminated and viewed at fairly large angles. That resulted in a large energy spread of the scattered electrons so the resolution was limited to about 500Å due to chromatic aberration. Since such a resolution could be achieved more readily in scanning microscopes, the method was abandoned. However for single crystal surfaces the situation is entirely different. If the surface can be maintained reasonably clean, strong diffraction spots can be obtained and the energy spread in the diffracted beam is usually small; thus the imaging of the surface can be performed in a manner similar to the dark field imaging of a thin crystalline specimen.
Fringe Field Effects in a Symmetric Magnetic Spectrometer
Authors: Kosiara A.
Published: June 2020

The energy loss of fast electrons in their interaction with biological macromolecules is of considerable interest. For this reason we have investigated a high resolution electron spectrometer to be attached to a scanning transmission electron microscope. For the design of the spectrometer we have considered a uniform field, window frame magnet with appropriately curved pole boundaries to correct median plane aberrations at one specific electron kinetic energy E.
Characteristics and Application of Temperature-Field Emitters
Authors: Tamura N. , Goto T. , Harada Y.
Published: June 2020

On account of its high brightness, the field emission electron source has the advantage that it provides the conventional electron microscope with highly coherent illuminating system and that it directly improves the, resolving power of the scanning electron microscope. The present authors have reported some results obtained with a 100 kV field emission electron microscope.

It has been proven, furthermore, that the tungsten emitter as a temperature field emission source can be utilized with a sufficient stability under a modest vacuum of 10-8 ~ 10-9 Torr. The present paper is concerned with an extension of our study on the characteristics of the temperature field emitters.
A High Vacuum Emission Chamber for Scanning Electron Microscopy
Authors: Bottoms W.R. , Haydon G.B. , Anderson L. J.
Published: June 2020

The performance of modem commercial electron optical systems is normally limited by the quality of the electron source and this area of the instrument invariably consumes the greatest portion of the maintenance time required by the equipment. The development of a “clean” high vacuum system for the emission chamber, of electron beam apparatus can offer the possibility of improved resolution as well as lower maintenance requirements. Among the benefits of an improved vacuum in the electron source region are increased filament life, and compatibility with high brightness in the emission chamber. One cost effective method for providing an improved vacuum environment for the electron source region on existing equipment is to replace the emission chamber with another which is provided with its own clean pumping system.
Diffraction Fine Structure and Contrast from Octahedral Voids in Nickel
Authors: Sprague J. A.
Published: June 2020

It is a well-recognized fact that planar interfaces, such as stacking faults and domain boundaries, can produce fine structure in an electron diffraction pattern consisting of satellites surrounding the main transmitted and diffracted beams. In some recent work, fine-structure darkfield images have been used to selectively study faulted dislocation loops lying on a specific set of lattice planes. It has been shown both theoretically and experimentally, however, that similar diffraction fine structure can be produced by the inclined faces of wedge-shaped crystals. The original work on these effects was done on wedges formed by the faces of MgO crystals and those formed by inclined twin boundaries in metals. The theory can be equally applied to internal "vacuum wedges" in metals formed by the faces of polyhedral cavities, such as the truncated octahedral voids observed in irradiated nickel.
Optical Properties of HVEM Accelerators
Authors: Strojnik A. , Scholl J.W. , Bevc V.
Published: June 2020

The electron accelerator, as inserted between the electron source (injector) and the imaging column of the HVEM, is usually a strong lens and should be optimized in order to ensure high brightness over a wide range of accelerating voltages and illuminating conditions. This is especially true in the case of the STEM where the brightness directly determines the highest resolution attainable. In the past, the optical behavior of accelerators was usually determined for a particular configuration. During the development of the accelerator for the Arizona 1 MEV STEM, systematic investigation was made of the major optical properties for a variety of electrode configurations, number of stages N, accelerating voltages, 1 and 10 MEV, and a range of injection voltages ϕ0 = 1, 3, 10, 30, 100, 300 kV).
Dynamical Scattering in Crystalline Biological Specimens. II. The Domain of Validity for Different Approximations
Authors: Jap Bing K. , Glaeser Robert M.
Published: June 2020

Unlike other complex dynamical scattering approximations, the phase object approximation and the higher order phase object approximation give an invertible relationship between the projected object potential and the transmitted wave function. These two approximations therefore offer an attractive solution for correcting the dynamical scattering effects in electron micrographs. There is, however, only a limited domain in terms of resolution, specimen thickness and electron energy in which the approximations are valid. We have evaluated the domain of validity for each approximation, using the criteria discussed in part I.

The multislice formulation of Cowley and Moodie was used as our point of reference to calculate the 'exact' diffracted wave function of organic crystals. Anhydrous Cytosine crystal and 'DISOPS' (Disodium 4-Oxypyrimidine-2-sulfinate Hexahydrate) were used as our test objects.
A New Method for Single Atom Specimen Preparation
Authors: Chiu W. , Glaeser R. M. , Prussin S.
Published: June 2020

A reliable method of confirming that one is able to produce single atom images in high resolution electron microscopy is to make a comparison of the number of atoms per unit area that is seen by the electron microscopic observations and the number per unit area as determined by a separate experimental technique of high accuracy. This report presents a method of preparinga specimen composed of a low distribution of gold atoms (ca. 1 atom/104 Å2) sandwiched between two ultra-thin carbon films, and also a method of measuring the gold atom density in the specimen by neutron activation analysis.

The specimen was prepared by evaporation onto a freshly cleaved mica substrate in a vacuum evaporator, as shown in Figure 1. One side of the vacuum chamber was used to prepare a thin carbon film according to the method of Williams and Glaeser (1972), and the other side was used to evaporate the gold atoms from a molybdenum strip, which had a micro-quantity of gold deposited on a 1 cm2 surface area from a previous evaporation.
Lattice Images at θ’ Precipitates in Al-3%Cu Alloy
Authors: Phillips V. A.
Published: June 2020

As part of a high resolution electron microscopic study of the precipitation sequence at 130°C in aluminum - 3% copper alloy, we studied G. P. [1], G. P. [2] or θ”, and θ’ precipitates by the lattice imaging technique. This approach proved valuable for phase identification and distinction. Examples of cros sed-lattice and c-plane lattice images at θ’ platelets will be presented here.

Slices were spark cut nearly parallel to {001} from a melt-grown single crystal of aluminum -3.0 wt. % copper, previously solution treated at540°C and water quenched. Slices were aged at 130°C in argon and hand ground. Discs were chemically, electrolytically or in one case ion thinned, and examined at 100 kV in a slightly modified Philips EM 300 microscope.

In the aluminum-copper system, the intermediate phases (G. P. zones and θ’) separate parallel to cube matrix planes, so that the slice orientation chosen resulted in two sets of platelets being parallel and one set normal to the beam.
Stereoscopic Methods in TEM
Authors: Thomas L. E.
Published: June 2020

The use of stereoscopy to characterize three-dimensional structures observed by TEM has become widespread since the introduction of instruments operating at 1 MV. In its emphasis on whole structures and thick specimens this approach differs significantly from conventional methods of microstructural analysis based on three-dimensional image reconstruction from a number of thin-section views. The great advantage of stereo derives from the ability to directly perceive and measure structures in three-dimensions by capitalizing on the unsurpassed human ability for stereoscopic matching of corresponding details on picture pairs showing the same features from different viewpoints. At this time, stereo methods are aimed mainly at structural understanding at the level of dislocations, precipitates and irradiation-induced point-defect clusters in crystal and on the cellular level of biological specimens. 3-d reconstruction methods have concentrated on the molecular level where image resolution requirements dictate the use of very thin specimens.

For the most part the stereo methods used in TEM are direct and unsophisticated. Stereo pairs of micrographs are taken by tilting the specimen to record two views of the same structural features from viewpoints ten or so degrees apart.
Metaphase Chromosomes in the Scanning Proton Microscope
Authors: Escovitz William H. , Fox Timothy R. , Levi-Setti Riccardo
Published: June 2020

Radiation damage of biological specimens has become a great concern of scientists in high resolution microscopy. Although modern refinements have pushed the ultimate resolution of microscopes below 5Å, specimen damage and preparation techniques have thwarted the realization of this resolution in biological molecules near their natural states. Because Scanning Transmission Ion Microscopy (STIM) with protons is thought to be much more damaging than electron microscopy, critics have doubted the applicability of proton microscopy to biological research, especially at high resolution. As a first step in exploring proton-beam induced damage in biological material, whole-mount chromosomes have been imaged at low resolution by proton microscopy for the first time. After prolonged proton irradiation, the same chromosomes were examined by Conventional Transmission Electron Microscopy (CTEM).

Figure 1 is a bright-field proton micrograph of a chromosome obtained from human peripheral lymphocytes. The specimen, prepared by Dr. H. M. Golomb, is unstained and critical-point dried.
Studies of the Crystalline Yolk Complex from Xenopus Laevis
Authors: Collins M.L. , Ohlendorf D.H. , Banaszak L.J.
Published: June 2020

Yolk platelets isolated from oocytes of Xenopus laevis contain a lipoprotein-phosphoprotein complex arranged in highly ordered microcrystals. The dimeric lipoprotein, lipovitellin, contains about 20% lipid and is complexed with two molecules of a smaller, highly phosphorylated protein, phosvitin. It has been possible to obtain both x-ray data and electron images of the negatively stained lattice. We are trying to use these two approaches to derive a model for the lipovitellin-phosvitin complex. To do this, it has been necessary to: 1) correlate the parameters obtained from x-ray measurements with those from negatively stained lattices, and 2) determine the number of molecules in the unit cell.

The x-ray data from wet native crystals indicated an orthorhombic unit cell with dimensions a = 88.5, b = 174.8, and c = 198.9 Å (Ref. 1). Lyophilized native, and wet and lyophilized uranyl acetate stained crystals also produced similar x-ray powder photographs. The cell dimensions of lyophilized uranyl acetate stained crystals were a = 82.6, b = 159.8, and c = 180.4 Å.
Hepatitis A Antigen in Liver, Bile and Stool
Authors: Jackson D.R. , Hoofnagle J.H. , Schulman A.N. , Dienstag J.L. , Purcell R.H. , Lorenz D. , Barker L.F.
Published: June 2020

Using immune electron microscopy Feinstone et. al. demonstrated the presence of a 27 nm virus-like particle in acute-phase stools of patients with viral hepatitis, type A, These hepatitis A antigen (HA Ag) particles were aggregated by convalescent serum from patients with type A hepatitis but not by pre-infection serum. Subsequently Dienstag et. al. and Maynard et. al. produced acute hepatitis in chimpanzees by inoculation with human stool containing HA Ag. During the early acute disease, virus like particles antigenically, morphologically and biophysically identical to the human HA Ag particle were found in chimpanzee stool. Recently Hilleman et. al. have described similar particles in liver and serum of marmosets infected with hepatitis A virus (HAV). We have investigated liver, bile and stool from chimpanzees and marmosets experimentally infected with HAV. In an initial study, a chimpanzee (no.785) inoculated with HA Ag-containing stool developed elevated liver enzymes 21 days after exposure.
SEM Study on the Etiology of Pseudofolliculitis Barbae
Authors: Bernstein E. O. , Kairinen E.
Published: June 2020

Pseudofolliculitis barbae (PF) is a dermatological disorder affecting approximately 50%. of black men who shave. The disease is characterized by ingrown hairs and attendant papules, pustules or vesicles ("razor bumps") which can occur over the entire beard area but which are most prevalent in the submandibular region. While it is generally accepted that the disease is of biological origin, PF appears to be triggered by shaving which in turn leads to the immediate cause of the disorder, ingrown hair formation. However, differences of opinion exist as to the basic etiology of PF--that is, how ingrown hair formation occurs in certain individuals and not others. Therefore a comparison of the skin, hair and post-shave beard hair regrowth patterns of "normal" and PF-prone black and white men by scanning electron microscopic (SEM) examination of polyethylene replicas was undertaken to determine the causes of ingrown hair formation.
The Effect of Experimental Endolymphatic Hydrops (ELH) on the Endolymphatic Sac (ELS) in the Lemon Shark: An SEM Study
Authors: Kaufman Arenberg I. , Rauchbach E. , Murray J.P. , Spector G.J.
Published: June 2020

The role of the endolymphatic sac (ELS) in the pathogenesis of endolymphatic hydrops (ELH) or Meniere's disease is considered of great importance. An experimental model of ELH, the histopathologic correlate of Meniere's disease, has been utilized to study the effect of excess endolymph and endolymphatic hypertension on the inner ear of the lemon shark (Negation brevirostris). This study investigates the changes which occur to the ELS when the ELH is produced either by cautery of the external endolymphatic duct (ELD) orifice or by ligature of the external ELD after 6 weeks to 6 months postoperatively. All specimens (n = 4 normal n = 6 cautery hydrops, n = 4 ligature hydrops) were routinely prepared for SEM by the critical point method of Smith and Finke and photographed at 20 KV on a Cambridge Stereoscan Mark II. The normal intermediate portion of the ELS shows multiple rugae or folds and true villi (Fig. 1) to increase surface area for the resorbtion of endolymph.
Transmission Electron Microscopy of the Brenner Tumor. Contribution to the Histopathogenesis
Authors: accarini I.M. B
Published: June 2020

The histogenetic interpretation of the Brenner tumor remains obscure, despite the many contributions that attempts to explain their origin.

Six human ovaries containing islands of Brenner tumors were studied by histologic procedures and by the electron microscope; special stains, PAS, Oil red 0, toluidin blue and Wilder reticulum were also used. Fresh tissue was fixed in 3% glutaraldehyde, embedded in Epon, stained with Uranyl-acetate, Lead citrate and viewed in RCA E.M. The islands of tumor were located in the cortex, in the stroma or in the deep medulla; they were classified in developing, well developed, and degenerated one, depending upon the comparison of the histologic findings with the ultrastructure of the cytoplasmic organelles. These islands were set in a dense fibrous tissue in the stroma. In one case, the tumor was in the periphery of an ovarian fibroma developed in the ovarian cortex.

The ultrastructure of the cells were identical, except for the different degree of degeneration, noted in some cells.
cis—Dichlorodiammineplatinum (II) and its Effect on Microfilaments in Mammalian Cells
Authors: Aggarwal S.K. , McAllister P.
Published: June 2020

The regression of various tumors after cis-dichlorodiammineplatinum (II) (cis-Pt (II) treatment has been suggested to be mediated through mitotic inhibition and enhancement of the immune system. Present study illustrates the possible action of cis-Pt (II) on microfilaments and their role in the prevention of cytokinesis.

Sarcoma-180 ascites cells in culture were treated with cis-Pt(II) (5ppm; 2 μg/ml) for intervals of 15, 30, 60 and 120 minutes. Controls were incubated in culture medium without cis-Pt (II) . Both the treated and non-treated cultures were then glycerinated and incubated with heavy meromyosin (HMM) (Ishikawa, et al., 1969. J. Cell Biol., 43, 312). Heavy meromyosin was prepared from myosin (Lowery, et al., 1969, J. Mol. Biol., 42, 1) using trypsin as inhibitor. Cell cultures treated with cis-Pt(II) for 30 minutes were also transferred to fresh medium containing 25μg/ml cytochalasin B and 1% dimethyl sulfoxide (DMSO) for 2-24 hours.
Influence of Vagotomy on Duodenal Fat Absorption
Authors: Lamb James C. , Nopanitaya Waykin , Shinoda Brian A.
Published: June 2020

This study was undertaken to evaluate the effect of unilateral cervical vagotomy on duodenal fat absorption in rats. Increase in fecal fat has been reported following vagotomy. This study demonstrates changes in the duodenal absorptive cell of rats fed vegetable oil when their vagus nerve was previously sectioned on the right side of the neck.

Female white rats of a Wistar strain weighing approximately 300 gm were either vagotomized or underwent a sham operation two weeks before tissues were removed for study. The animals were fasted for 48h then fed 2ml Wesson oil through an intragastric feeding tube. One hour later the animals were sacrificed and a segment of the duodenum was removed and processed for transmission electron microscopic analysis.

U1trastructural findings in the duodenal epithelial absorptive cells of the sham-operated, oil-fed controls (Fig. 1) were similar to those previously reported.
Ultrastructure of Proliferative Ileitis in Hamsters-Intestinal Amyloidosis
Authors: Jourden Martin G. , Kim James C. S. , Williams Christine S. F.
Published: June 2020

Proliferative ileitis in hamsters is one of the unique diseases characterized by dehydration, diarrhea, and emaciation. It has been repeatedly found as a major obstacle by those making use of this species in long term research projects. Intensive light microscopic studies have already been conducted; cellular hyperplasia, along with goblet cell hypoplasia and inflammatory changes were observed. Even though non-specific viral agents and other bacterial organisms have been recovered, the overall etiology still remains unknown.

Since ultrastructural studies of this problem had not been made, we have examined the ileum of two sick hamsters in hopes of elucidating the etiology and other accompanying ultrastructural changes. The control preparation was found to have numerous, tall microvilli of uniform height and size (Fig. 1). Cytoplasmic organelles, as well as the junctional complexes and desmosomes, were clear and distinct. Numerous mitochondria of various size and shape were found in the underlying region of the brush border (Fig. 2).
Biogenic Amine Identification by Analytical Electron Microscopy
Authors: Wood Joe G. , Harling David
Published: June 2020

X-Ray microanalysis with the analytical electron microscope (AEM) can be a valuable tool in studying the nervous system. This instrument can identify heavy metal reaction products developed to localize specific biogenic amines (BAs). The reaction involves the formation of an isoquinoline derivative between the unsubstituted BA and glutaraldehyde. This isoquinoline reacts with a chromate salt and the Cr is incorporated into the reaction product.

Tissues used in these studies were cat adrenal medulla and monkey median eminence. All tissues were fixed in 4% glutaraldehyde plus 1% sodium molybdate in 0.2 M sodium cacodylate buffer (pH 7.2) for two hours. Tissues were then incubated in a potassium dichromate preparation (pH 4.1) in the same cacodylate buffer. Following incubation, tissues were treated overnight in 4% paraformaldehyde in the cacodylate buffer. Subsequently, alternate blocks were treated with 1% osmium tetroxide. Thin sections were examined in the JEOL-100C Electron Microscope equipped with a goniometer stage, scanning attachment and a Kevex detector/multichannel analyzer system, utilizing a specimen-to-detector distance of less than 20mm.
Morphological Basis for the Photomechanical Response in the Photoreceptors of the Vertebrate Retina
Authors: Adomian Gerald E. , Sjöstrand Fritiof S.
Published: June 2020

The photoreceptors In certain vertebrate retinas respond mechanically to light. This photomechanical response may Involve extensive changes In cell length. These changes are localized within the myoid region of the inner segment. The responses of rod and cone receptor cells to light are reciprocal. In darkness, the cone myoid Is extended, while that of the rod is shortened. In light, the situation is reversed. The machinery responsible for this intriguing phenomenon has not been elucidated. Therefore, the objective of the present study was to Investigate the morphological basis for myoid elongation and shortening.

Retinas from a hybrid of Ictalurus melas and Ictalurus nebulosus were prepared for electron microscopy after varying degrees of light adaptation. Six maximally light adapted animals, four semi-adapted animals, and four maximally dark adapted animals were analyzed quantitatively.

Myoids from the shortened receptor cells generally consisted of a supranuclear region which measured approximately four and seven microns In diameter and about nine and five microns in length, In rods and cones, respectively.
Photoelectron Microscopy of Biomembranes: Observation of External Photoemission from Spinach Chloroplasts
Authors: Dam Rudy J. , Lesch George H. , Deamer David W. , Griffith O. Hayes
Published: June 2020

Understanding the detailed structure and function in biological membranes is a current problem in molecular biology. Ultrastructural studies, based on the ability to discriminate chemically different sites on the membrane surface, would provide crucial data relevant to a number of questions. This paper describes a promising microscopic technique, based on the photoelectric effect, which has this capacity. A sample is irradiated with UV light above the photoelectric threshold, and the resulting photoelectrons are accelerated and focused by conventional electron optics. Figure 1 illustrates schematically the technique of photoelectron microscopy (PEM) in comparison with two more familiar techniques, fluorescence microscopy and transmission electron microscopy (TEM). Efforts to utilize the photoelectric effect to study biological surfaces were begun in this laboratory in 1968 and the initial images of organic surfaces and a mammalian tissue are described by Griffith et al. We report here the first photoelectron image of plant organelles.
SEM of the Cecal Morphology in the Domestic Chicken
Authors: Witlock Dale R.
Published: June 2020

McNab stated that the cecum may play a nutritional role when normal modes of digestion in the small intestine are impaired. Calhoun on the basis of light microscopic studies indicated that the cecal villi resemble those found in the small intestine. The scanning electron microscope (SEM), with increased resolution, depth of focus, and sampling power; which affords a three dimensional image was the ideal tool for reexamining the morphology of the cecal mucosa.

Tissue was removed from four areas of the ceca of 8 White Leghorn cockerels 2 weeks old. Area A, the cecal neck region, Area B, the portion where the neck widens to form the pouch, Area C, the mid-cecal pouch region and Area D, 3-5 mm from the blind end of the ceca. This tissue was fixed (2% glutaraldehyde in 0.2M cacodylate-HCl, pH 7.4), ethanol dehydrated and critical point dried. Freeze fractured material was prepared by the methods of Humphreyset al. The dried specimens were mounted on stubs and coated with gold palladium.
Scanning Electron Microscopy of Endocardial Surface of Right Atrium in Mice
Authors: González-del-Pliego Margarita , Miguel Salazar  , Alfredo Ferra-Velasco
Published: June 2020

The development of the scanning electron microscope (SEM) has added increasing knowledge to the structure of the various organs, giving us a new dimension to the study of their constituents. Although there are few studies on cardiac tissue using the SEM, these are mainly oriented to describe the myocardial cytoplasmic elements and the myocardial cell surface.

Interested in our laboratory in cardiac microcirculation, one of the studies in progress is the openning of the arterioluminal and Thebesian vessels into the cardiac cavities. In the present communication we describe the endocardial surface of the right atrium in mice with particular emphasys on the foraminula of vessels openning into the atrium by using the scanning electron microscope.

Right atria from mice were fixed immediately after death in 2.5% cacodylate buffered-glutaraldehyde, pH 7.4 for 3 hrs at 4°C and dehydrated in a graded series of acetone.
Non-Specificity of a “Selective” Stain for Sarcoplasmic Reticulum in Cardiac Cells
Authors: Sybers H. D. , Gann M. K.
Published: June 2020

The development of a selective staining procedure for cardiac sarcoplasmic reticulum has been reported and should be of great value in studies of pathologic conditions in which the sarcoplasmic reticulum may be altered. To be useful for this purpose, however, it must be reliably reproducible and specific enough so that other membrane systems are not stained, resulting in misinterpretation. We have applied the procedure of Waugh and Sommer in the study of rabbit heart and have found excellent visualization of the interstitial spaces and transverse tubular system, however, staining of the sarcoplasmic reticulum did not occur. The hearts were fixed with 1.6% glutaraldehyde in 300 mOsm cacodylate buffer, pH 7.2, for 5 min. by retrograde coronary artery perfusion via an aortic cannula. The perfusion was then switched to 0.05 M Tris (pH 7.6) in sodium chloride (total mil1iosmolarity = 300). After 5 min., the perfusion was switched to Tris containing 100 mg% 3-3' Diaminobenzidine tetrahydrochloride (DAB) and 0.01% hydrogen peroxide for 20 min.
Low Temperature Beam Damage to Biological Specimens in the Electron Microscope
Authors: Ramamurti K. , Crewe A. V. , Isaacson M. S.
Published: June 2020

It is now well recognized that serious limitations to resolution of details obtainable in biological specimens are imposed by the damage inflicted on the specimen by the electron beam. Several techniques, such as minimal exposure and signal averaging, have been proposed to overcome these limitations (see Ref. 1 for brief discussions and further references to literature). However, it would be clearly desirable to minimize the damage itself. A promising approach appears to be to cool the specimen to cryogenic temperatures.

It should be emphasized that we do not expect any significant change in the primary damage rate of individual molecules, but we may hope that fragmentation would be reduced which would in turn, reduce the rate of mass loss, and secondary damages.

Several studies with cooled specimens have been reported, but most of the results seem to be incluclusive and some of them even mutually contradictory.
Preparation of Frozen-Dried Tissue for Transmission Electron Microscopy: A Simple and Dependable Method
Authors: Terracio Louis , Coulter David
Published: June 2020

An inexpensive and dependable method for freeze-drying biological tissue for transmission electron microscopy has been developed. Reproducible results can be attained if the following procedure is carefully followed.

1) The primary components for the freeze-drier are shown assembled in figure 1. Preheat the 1000 ml pumping chamber containing 5 Å molecular sieve for at least 12 hours at 150° C. Connect the isolation valve to the chamber, close the valve, and stopper the flask with a #8 Neoprene stopper. Supporting the chamber with a ring stand clamp, place it in a Dewar filled with liquid nitrogen and allow it to equilibrate. Connect the drying chamber to the isolation valve and set it up in another Dewar without liquid nitrogen. Remove the #7 Neoprene stopper with its thermometer and specimen block and suspend it apart from the drying chamber with a ring stand clamp. The bulb of the thermometer is not tightly positioned in the specimen block at this time but is about ” above it.
Trimethyllead Acetate as a DNA Backbone Stain for Electron Microscopy
Authors: Kosiara A. , Douglass K. , Beer M.
Published: June 2020

In the process of developing electron microscopic techniques for sequencing DNA it has become clear that in addition to selective heavy metal labeling of the bases it will be necessary to label the phosphate backbone as well. We have studied the suitability of trimethyllead acetate as a backbone label for high resolution electron microscopy of DNA.

The binding of the trimethyllead ion to acetate was studied by acid-base titration and DC conductivity, while the binding to DNA was determined by equilibrium dialysis. Most measurements were done in solutions of low ionic strength, approximating the conditions for staining reactions.

Defining the equilibrium constants,

and choosing Kaand Kbto fit the titration curve we obtain the experimental values given in Table I.

The conductivity of PbMe3Ac was measured in water and in 50%, dioxane. The data were analyzed according to the method of Fuoss and the results are given in Table I.
Depletion and Reconstitution of Active E. Coli Ribosomes
Authors: Boublik M. , Hellmann W. , Jenkins F.
Published: June 2020

Correlations between structure and function of biological macromolecules have been studied intensively for many years, mostly by indirect methods. High resolution electron microscopy is a unique tool which can provide such information directly by comparing the conformation of biopolymers in their biologically active and inactive state. We have correlated the structure and function of ribosomes, ribonucleoprotein particles which are the site of protein biosynthesis. 70S E. coli ribosomes, used in this experiment, are composed of two subunits - large (50S) and small (30S). The large subunit consists of 34 proteins and two different ribonucleic acid molecules. The small subunit contains 21 proteins and one RNA molecule. All proteins (with the exception of L7 and L12) are present in one copy per ribosome.

This study deals with the changes in the fine structure of E. coli ribosomes depleted of proteins L7 and L12. These proteins are unique in many aspects.
Fundamental Studies of Bacterial Leaching Using Bio-Physical Techniques of Transmission Electron Microscopy
Authors: Berry V.K. , Murr L.E.
Published: June 2020

The role of microorganisms and their reaction with minerals are comparatively newer research areas in the general area of chemical mining, and have considerable scope of further development. The most commonly studied reactions of this type have been associated with microorganisms characterized as Thiobacillus thio-oxidans and Thiobacillus ferroxidans. These microorganisms have the ability to oxidize heavy metal sulfides and elemental sulfur to water soluble sulfates; and ferrous iron to ferric iron.

The attachment location of biological microorganisms on minerals has not been reported in the literature as it relates specifically to biogenic metallurgical processes, although an attempt to describe the mode and character of bacterial attachment has been made by some workers. In the current investigation, a thermophillic microbe previously described by Brierley and Brierley and suggested to have a relationship with Sulfolobus was used. This microorganism exhibits an intracellular retractile body un-like Sulfolobus.
Trophozoites of Pathogenic Naegleria: Scanning Electron Microscope Study
Authors: Julio Martinez A. , Clifford Nelson E. , Fultz Doris G. , Geeraets Ragnit
Published: June 2020

Scanning electron microscopy (SEM) can serve as a valuable supplement to transmission electron microscopy (TEM) in the study of pathogenic protozoa. Details of overall form and structure of surface and organelles which may have a role in pathogenicity may be revealed. TEM studies on Naegleria have contributed much to understanding the extraordinary virulence of this ameba, but some remaining questions may be resolved by SEM. This report describes a technique which has proven useful in preparing SEM specimens. Naegleria ameba trophozoites adhere strongly to the surface on which they are growing. In culture tubes, amebae will multiply on the wall. Naegleria tends to grow from the top of the fluid downward and may multiply until a solid monolayer develops. If a strip of plastic film is introduced, the growth on the strip can be observed by direct microscope viewing through the wall of the tube.
Studies on the Pellicular Complex of the Exocrythrocytic Merozoites of the Avian Malarial Parasite (Plasmodium lophurae)
Authors: Meszoely C. A. M. , Beaudoin R. L. , Erbe E. F. , Steere R. L.
Published: June 2020

Plasmodium lophurae grown in monolayers of cells derived from turkey brains was freeze-fractured after fixation in 1.25% gluteraldehyde. The fixed material was placed in an ascending series of glycerol buffer until a 40% concentration was reached. This preparation was then frozen and fractured at -190°C under vacuum. Both fracture surfaces of the specimen were simultaneously shadowed and carbon coated to obtain complementary replicas. The replicas were studied with the JEM 100-B transmission electron microscope.

Previous studies on stained ultrathin sections of the merozoites of mature schizonts show the merozoite to be surrounded by two membranes and an innermost microtubular system. In addition to this pellicular system of the merozoites, the entire schizont is surrounded by a loose limiting membrane. Our studies revealed splitting of the two membranes enclosing the exoerythrocytic merozoite. This resulted in the presence of four fracture faces, each with its own distinct topography.
Synchrony of Digestion of SV40 DNA by Exonuclease III Determined by EM
Authors: Wu Ray , Ruben G. , Siegel B. , Spielman P. , Jay E.
Published: June 2020

A method for determining long nucleotide sequences of double-stranded DNA is being developed. It involves (a) the synchronous digestion of the DNA from the 3' ends with EL coli exonuclease III (Exo III) followed by (b) resynthesis with labeled nucleotides and DNA polymerase. A crucial factor in the success of this method is the degree to which the enzyme digestion proceeds synchronously under proper conditions of incubation (step a). Dark field EM is used to obtain accurate measurements on the lengths and distribution of the DNA molecules before and after digestion with Exo III, while gel electrophoresis is used in parallel to obtain a mean length for these molecules. It is the measurements on a large enough sample of individual molecules by EM that provides the information on how synchronously the digestion proceeds. For length measurements, the DNA molecules were picked up on 20-30 Å thick carbon-aluminum films, using the aqueous Kleinschmidt technique and stained with 7.5 x 10-5M uranyl acetate in 90% ethanol for 3 minutes.