bluuebunny/crossref_metadata_2025 huggingface dataset:
Accumulation and Toxicity of Cadmium in Chironomus Thummi
Authors: Seidman L.A. , Bergtrom G. , Remsen C.C.
Published: June 2020

Heavy metal pollutants which enter aquatic ecosystems are of concern because: (1) Metals often accumulate in exposed organisms leading to biomagnification at higher trophic levels. (2) Fitness of aquatic populations may be decreased by sublethal exposures. We are investigating the mechanisms of cadmium accumulation and toxicity in daphnids (planktonic microcrustacea) and chironomid larvae (benthic dipteral. This report focuses on Chironomus thummi.
The Role of Collagen, Fibronectin, Chondronectin and Laminin in Cell Adhesion
Authors: Kleinman Hynda K. , Martin George R.
Published: June 2020

Most cells other than blood cells interact with extracellular matrices composed of various types of collagens, proteoglycans and a newly described group of glycoproteins termed the attachment proteins. Variations in the composition of the extracellular matrix determine the uniqueness of tissues, such as cartilage, bone, dermis and basement membranes. These matrices have numerous functions, including providing structural support to rigid tissues (cartilage, tooth and bone), regulating the passage of macromolecules (kidney basement membrane), and allowing tissues to stretch (blood vessels and skin). In addition, these matrices have potent influences upon the cells which populate them. The anchorage, growth, differentiation, and motility of the resident cells are all determined by their surrounding extracellular matrix. Such matrices are critically important in embryonic development, tissue organization and wound healing.
Presence of Clathrin at Adhesion Sites in Phagocytosing Macrophages
Authors: Aggeler J. , Heuser J.E. , Werb Z.
Published: June 2020

Phagocytosis of particles by macrophages may be similar to cell spreading on a substratum, in that a dense network of actin filaments appears beneath the plasma membrane in both cases. When viewed in broken-open or detergent- extracted cells, cytoskeletal filaments are observed to form focal attachments to the plasma membrane and to the cytoplasmic surface of phagosomes. Hartwig et al. have presented a model of phagocytosis in which an actin-binding protein alters the organization of subplasmalemma1 actin filaments in such a way that the plasma membrane is forced up over the particle to form the phagosome. Their evidence indicates that similar actin-binding proteins may function during cell spreading.
Stagger and Superposition in Actin Paracrystal Polymorphism
Authors: Fowler W.E. , Aebi U.
Published: June 2020

Polylysine, in the presence of KC1, induces both muscle and non-muscle actins to form paracrystals. These paracrystals, like those induced by Mg, are made up of laterally associated actin filaments; however, paracrystals induced by polylysine exhibit a polymorphism that is not observed using other paracrystal induction methods. To fully exploit the highly ordered (to at least 2.5 nm) polylysine-induced paracrystals in the three-dimensional reconstruction of the actin filament (work in progress), it is necessary to understand the basis for the observed polymorphism.
More Types of Inclusion Found in Colchicine-Treated, Cultured Rat Hepatocytes
Authors: Green I. S. , Samsonoff W. A. , Galivan J. , Fox P.
Published: June 2020

Primary monolayer cultures of hepatocytes provide a convenient model system for the study of hepatic parenchymal cell function. Recently it has been shown that colchicine toxicity to cultured rat hepatocytes can be prevented by the addition of certain hormones (glucagon, hydrocortisone and insulin) to the growth medium. Using transmission electron microscopy (TEM), we have characterized the structural properties of cultured hepatocytes treated with colchicine with and without hormone supplement.
Complex of 40S Ribosomal Subunit with Initiation Factor eIF-3
Authors: Boublik M. , Hellmann W. , Jenkins F. , Staehelin T. , Trachsel H.
Published: June 2020

Ribosomes are intracellular organelles present in all organisms as an integral part of their protein-synthesizing system. Biochemical evidence suggests that ribosomes are engaged in all phases of protein synthesis - initiation, elongation, and termination of a polypeptide chain. However, the mechanism of ribosomal involvement in any of these steps has yet to be established. At present, the most direct approach to the studies of structure-function relationship of ribosomes is by high resolution electron microscopy.
Osmiophilic Lamellated Bodies Between the Gill Lamellae of Fish
Authors: Liu K. C. , Sun G. Y.
Published: June 2020

The presence of osmiophilic, lamellated bodies in the alveolar surface of the lung and the functional importance of those bodies in faciliatating gaseous exchange have been established in animals including repitilia, avian, and mammals. According to the available literature source that similar bodies were reported in the epithelial cells of fish gills, but a more detailed study in this area is still lacking.
Analytical Electron Microscopy (AEM) of Meningeal Cells Exposed to Particulate Cobalt During Studies of Experimental Epilepsy
Authors: Frederickson R.G. , Ulrich R.G. , Culberson J.L.
Published: June 2020

Metallic cobalt acts as an epileptogenic agent when placed on the brain surface of some experimental animals. The mechanism by which this substance produces abnormal neuronal discharge is unknown. One potentially useful approach to this problem is to study the cellular and extracellular distribution of elemental cobalt in the meninges and adjacent cerebral cortex. Since it is possible to demonstrate the morphological localization and distribution of heavy metals, such as cobalt, by correlative x-ray analysis and electron microscopy (i.e., by AEM), we are using AEM to locate and identify elemental cobalt in phagocytic meningeal cells of young 80-day postnatal opossums following a subdural injection of cobalt particles.
Ultrastructural Investigation of Spontaneous Pituitary Adenomas in Aging Sprague-Dawley Rats
Authors: McComb D. J. , Beri J. , Zak F. , Kovacs K.
Published: June 2020

Investigation of the spontaneous pituitary adenomas in rat have been limited mainly to light microscopic study. Furth et al. (1973) described them as chromophobic, secreting prolactin. Kovacs et al. (1977) in an ul trastructural investigation of adenomas of old female Long-Evans rats, found that they were composed of prolactin cells. Berkvens et al. (1980) using immunocytochemistry at the light microscopic level, demonstrated that some spontaneous tumors of old Wistar rats could contain GH, TSH or ACTH as well as PRL.
Ultrastructure of the Omphalomesenteric Duct Rest in the Umbilical Cord at Term
Authors: Clark B. A. , Okagaki T.
Published: June 2020

Vestiges of the omphalomesenteric or vitello-intestinal duct and the pathologic implications attributed to these remnants have been treated in great detail by several investigators. Persistence of the omphalomesenteric duct is associated with such conditions as Meckel's diverticulum, umbilical fistula, mucosal polyps, and sinuses or cysts of the umbilicus. Remnants of the duct in the umbilical cord, although infrequent, are located outside of the triangle formed by the two umbilical arteries and the umbilical vein, are usually discontinuous and are often represented by a small lumen lined by cuboidal or columnar epithelium. This study will examine the ultrastructure of these cells.
Localization of Anionic Binding Sites in the Glomerular Basement Membrane of a Cold Water Teleost
Authors: Boyd R. B. , DeVries A. L.
Published: June 2020

The blood of the winter flounder, Pseudopleuronectes americanus, a cold water teleost, is characterized by the presence of small (3000-5000d) anionic (pI 4.1-4.5) peptides that lower the freezing point of the blood. These peptides exhibit a seasonal variation, occurring only in the winter when the fish is exposed to temperatures near or below the freezing point of sea water. The antifreeze molecule is retained by the glomerular kidney of the fish even through inulin, of comparable weight, is rapidly filtered from the blood into the urine. We have examined the glomerular filtration barrier in the winter flounder, using the electron-dense ferritins, in order to identify anionic sites that might function to conserve these peptides.
Three-Dimensional Ultrastructure of Agmenellum Quadruplicatum
Authors: Nierzwicki S. A. , Balkwil D. L. , Stevens S. E.
Published: June 2020

Agmenellum quadruplicatum is a unicellular cyanobacterium (blue-green alga) measuring ≃2.5 x 5.0 μm. The basic ultrastructural features of this organism have been characterized previously, but there have been no reports fully describing the three-dimensional organization of these features within the cell. Yet, such information would be valuable in regard to understanding the mechanism by which cell structures in cyanobacteria function. The purpose of this study, then, was to reconstruct for the first time the three-dimensional arrangement of fine structures in a cyanobacterial cell.
Cellular Effects of Herbicide Simazine on Blue-Green Algae
Authors: Mehta R.S. , Hawxby K.W.
Published: June 2020

This study is sought to compare the effects of herbicide simazine (2-chloro 4,-6-bis (ethylamino)-S-triazine) on cellular corrponents of control and the treated cells of the blue-green alga (cyanobacterium) Anacystis nidulans, which are well defined and documented. The extent to which this initial interpretation of observations are realities, must be determined by biochemical and perhaps cytochemical techniques as well.
A One-Step Method for Re-Embedding Paraffin Embedded Specimens for Electron Microscopy
Authors: Chien Kai , de Velde Robert L. Van , Ileusser Robert C.
Published: June 2020

The need to re-embed paraffin embedded material for electron microscopy is occasionally encountered in surgical pathology. The purpose of this abstract is to demonstrate a simple procedure for the retrieval of paraffin embedded tissues which eliminates rehydration, dehydration and combines deparaffinization and osmication in one step, and allows effective diagnostic interpretation of tissue lesions.
The Imaging Problem in the X-Ray Microanalysis of Matrix-Free Extracellular Spaces in Frozen-Hydrated Tissue Sections
Authors: Hall T. A. , Gupta B. L.
Published: June 2020

Quantitative X-ray microanalysis of diffusible elements is commonly practised with frozen-dried cryosections. However the contents of matrix-free extracellular spaces cannot be preserved during freeze-drying; the elements in such spaces can be analysed quantitatively only in specimens in the frozen-hydrated state. One obstacle discouraging wider use of this approach is that the low image-contrast in frozen-hydrated sections makes it difficult to identify the fields one wants to analyse. Here we shall illustrate the problem and consider several bases for coping with it.
Electron Probe Microanalysis of Frozen Hydrated Kidneys, Isolated Cells, and Cultured Cells
Authors: Lechene Claude
Published: June 2020

Electron probe microanalysis of frozen hydrated kidneys

The goal of the method is to measure on the same preparation the chemical elemental content of the renal luminal tubular fluid and of the surrounding renal tubular cells. The following method has been developed. Rat kidneys are quenched in solid nitrogen. They are trimmed under liquid nitrogen and mounted in a copper holder using a conductive medium. Under liquid nitrogen, a flat surface is exposed by sawing with a diamond saw blade at constant speed and constant pressure using a custom-built cryosaw. Transfer into the electron probe column (Cameca, MBX) is made using a simple transfer device maintaining the sample under liquid nitrogen in an interlock chamber mounted on the electron probe column. After the liquid nitrogen is evaporated by creating a vacuum, the sample is pushed into the special stage of the instrument. The sample is maintained at close to liquid nitrogen temperature by circulation of liquid nitrogen in the special stage.
Computer Simulation and Analysis of High Resolution Electron Microscope Images and Diffraction Patterns of Semiconductor Interfaces
Authors: Krakow William
Published: June 2020

In recent years there has been considerable interest in the atomic structure of transition metal silicides and the interfacial region they form with crystalline Si. This is of prime importance in increasing the understanding of the origin of Schottky barrier formation and ohmic contacts in diode applications. High resolution transmission electron microscopy (TEM) offers the potential of direct observation of atomic image detail at the interface which may be interpreted in terms of atomic position models, the diffraction process at the interfacial region and the microscope performance. To this end, it has recently been demonstrated that TEM computer image simulation experiments on the Pd2Si/Si interface could be obtained that show remarkable agreement with real microscope experiments. Also exploratory STEM microdiffraction computer simulation experiments have been performed to demonstrate space group symmetry and atomic position determination to a fraction of a unit cell dimension in Pd2Si or Si.
Defects in Heavily-Doped MBE GaAs
Authors: Carter C.B. , DeSimone D.M. , Griem T. , Wood C.E.C.
Published: June 2020

Molecular-beam epitaxy (MBE) is potentially an extremely valuable tool for growing III-V compounds. The value of the technique results partly from the ease with which controlled layers of precisely determined composition can be grown, and partly from the ability that it provides for growing accurately doped layers.
Reflection Electron Microscopy (REM) of Surface Steps & Dislocations on GaP(110) & GaAs(110)
Authors: Hsu Tung , Iijima Sumio
Published: June 2020

Reflection electron microscopy (REM) in ultra high vacuum environment with heating stage has been reported by Osakabe, et al. In this paper, we present our results in REM imaging of single steps and dislocations using commercial electron microscopes (JEM-100B and Philips-400T) under ordinary pressure (10-7 torr) and room temperature.
Spatial Resolution of Stem and EDS in an AL-GE Alloy
Authors: Twlgg M. E. , McCarthy J. P. , Fraser H. L.
Published: June 2020

As part of an effort to better understand beam broadening and its deleterious effect on the spatial resolution of x-ray microchemical analysis employing STEM and EDS, we have been studying apparent concentration profiles in the vicinity of germanium precipitates in an aluminum matrix. Because of the limited solubility of aluminum in germanium, we know that the precipitates are almost completely composed of Ge; accurate knowledge of the composition of such precipitates facilitates the modeling of the apparent concentration profiles via Monte Carlo trajectory simulations.
Energy Loss Analysis of Oxygen Microprecipitates in Silicon
Authors: Chan I.Y.T. , Carpenter R. W. , Varker C. J. , Chang L. , Demer L. J.
Published: June 2020

The morphological forms of oxygen-containing precipitates and other defects in heat-treated silicon have been the subject of a number of TEM investigations, but little direct evidence has been given for the amount of oxygen in them and their crystallography. Electron energy loss spectroscopy appears to be the most promising microanalytical method for detecting and measuring the amount of oxygen present in these small precipitates. Yang, et al have reported evidence for oxygen in large precipitates (∿lμm) in heat-treated silicon, obtained by examining EL spectra taken from precipitate pit sites in etched Si foils. We report here ELS results from small Si-0 precipitates that formed in CZ silicon wafers during post-growth heat treatment. The interstitial oxygen concentration in the as grown Si was ∿2 x 1018 cm-3. Following growth the cut wafers were given a two step anneal: (1) 16 hrs. @ 800°C in nitrogen and (2) 16 hrs. @ 1050°C in dry oxygen. Transmission specimens were made by ion beam thinning.
Crystallographic Orientation Effects in X-Ray Production from Ordered Intermetallic Alloys
Authors: Pande C. S. , Sabatini R. L.
Published: June 2020

The dependence of characteristic, electron induced, x-ray production on beam orientation in crystalline solids has been predicted theoretically and observed experimentally by many researchers. This effect is analogous to the Borrmann effect in x-rays. The plane electron wave entering the crystal generates Bloch waves with nodes or antinodes at the center of the atoms. The amplitude of the Bloch waves depends upon the orientation, resulting in a variation in current density over the unit cell with incident beam direction. This effect is important when measuring chemical compositions in thin films of alloys (ordered and disordered) by energy dispersive x-ray analysis or by energy loss analysis. It has so far been tacitly assumed that if thin film criteria is satisfied, this orientation effect is negligible (if not too close to a Bragg reflection).
The Nature of Precipitates in Cat's-Eye Chrysoberyl
Authors: Marder J. M. , Mitchell T. E.
Published: June 2020

Introduction. Chrysoberyl (Al2BeO4) is a gem quality mineral which has the olivine structure. The lattice is orthorhombic, a = 0.549nm, b = 0.942nm and c = 0.443nm, with space group Pbnm. The structure is based on a hexagonal close packing of anions with half of the octahedral interstices occupied by Al cations and one eighth of the tetrahedral interstices occupied by Be cations. Chrysoberyl can also exist in a Cat's-eye (chatoyant) variety, the reason for which is unknown and is investigated in the present paper.
Microstructural Heterogenieties in a Commercial SiC Structural Ceramic:Hraem
Authors: Skiff W.M. , Carpenter R.W.
Published: June 2020

SiC refractories made by various pressing and sintering methods may contain structural and chemical heterogenieties similar to tljiose reported for Si3N4 base refractories. Although some earlier work on SiC did not reveal second phases, other oxidation experiments showed the reaction to take place heterogeneously, leading to the supposition that such heterogenieties may be present. In this work we examine a typical commercial SiC ceramic to determine the existence of such structural irregularities.
Tem Observation of Bubbles in He-Implanted α-Fe
Authors: Follstaedt D. M. , Myers S. M.
Published: June 2020

Helium has negligible solubility in metals, but in certain materials applications it is introduced athermally. This occurs, for example, through ion implantation from thermonuclear plasmas, tritium decay, and neutroninduced transmutation. Helium may have several detrimental effects, including grain boundary embrittlement, initiation of void swelling, and trapping of hydrogen isotopes. Hence a fundamental understanding of the behavior of He in metals is important. Implantation of He into a metal at room temperature usually leads to one of two microstructural configurations. At sufficiently low concentrations. He trapping by irradiation defects dominates.
Microstructure of Neutron Irradiated β-Si3 N4
Authors: Youngman R. A.
Published: June 2020

Recent interest in the use of ceramic materials as structural components, particularly the first wall, of proposed controlled thermonuclear fusion reactors has lead to investigation of their response to neutron irradiation at elevated temperature. One such structural ceramic is Si3 N4 which undergoes very little or no swelling after a large neutron dose at high temperatures.
On The Origin of Microtwins in Evaporated thin Films of Gold
Authors: King A. H.
Published: June 2020

In a recent paper, Treacy et.al. described a novel technique for comparing bulk and surface structures of defects in thin films. They demonstrated that surface relief effects are associated with microtwins in (100) single crystal evaporated thin films and surmised that these defects are formed by deformation of the film in handling rather than by "growth accidents" during evaporation, as had been assumed previously. During the course of a project involving deformation of thin film gold bicrystals the following observations were made partly corroborating the conclusions of Treacy et.al.
In-Situ Electron Microscopy of Heterogeneous Catalysts
Authors: Gai P. L.
Published: June 2020

Selective oxidation and ammoxidation of hydrocarbons using metal oxide and supported metal particle catalysts account for a substantial portion of key industrial chemicals and are therefore, important. The selectivity and activity are critically dependent upon the changes in the microstructure of the catalysts. Origin of such changes pose important problems in heterogeneous catalysis and understanding them may provide a better insight into the catalyst performance. Applications of electron microscopy (EM) techniques are particularly useful providing additional and new information about such changes.
Sem Analysis of Clad-Ceramic Coatings after Hot Corrosion Testing
Authors: Olson C. D.
Published: June 2020

Scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDX) have been used to study protective coatings on metals. Recently much interest has been generated in regard to the suitability of clad materials for application in a dynamic hot corrosive gas system. This interest stems not only from a standpoint of corrosion reduction (durability) but also from a standpoint of economics (reduction of consumption of scarce resources). Attention, therefore, is now being given to a class of materials that are arc plasma sprayed (APS) on metals. The APS technique produces a strong bond between the substrate material and the coating. This is due to oxide film break-down of the ASP material and the metal substrate at extremely high temperatures.
Microstructure of Surface Oxide Films on a Commercial Ods Alloy
Authors: Ramanarayanan T. A. , Raghavan M. , Petkovic-Luton R.
Published: June 2020

It is well known that the presence of yttria dispersoids in aluminum containing Oxide Dispersion Strengthened (ODS) alloys significantly improve the adherence of the protective AI2O3oxide scale during high temperature oxidation. However, the exact mechanism by which this improved adherence is brought about is not well understood. As a part of an investigation to study the mechanism of oxide adherence in a ODS alloy MA956, electron microscopic analysis of the oxide and metal/oxide interface was conducted and the results of the microstructural analysis are described here.
Microanalysis of Bismuth Molybdate Phases
Authors: Lyman C. E.
Published: June 2020

Bismuth molybdates are widely used as selective oxidation catalysts. Often several phases containing Bi and/or Mo are mixed together to obtain desired catalytic properties. While selected area electron diffraction can identify individual crystalline particles, diffraction techniques usually require considerable time for developing film and analyzing patterns. X-ray emission spectroscopy can identify individual phases containing two detectable elements within a few minutes while the operator is at the microscope.
Structure Determination of Ni3MO Using Convergent Beam Electron Diffraction
Authors: Kaufmana M.J. , Frasera H.L.
Published: June 2020

During a recent study aimed at determining the effects of microstructure on mechanical properties in some experimental Ni-Al-Mo superalloys, it has become apparent that precipitation of fine phases at sites such as grain boundaries plays a critical role. One such phase that has been observed is shown in Fig. 1; using energy dispersive x-ray analysis and selected area diffraction, this phase appears to be consistent with orthorhombic Ni3MO. Fully aged Ni3MO is indeed orthorhombic1, but the development of this structure has been reported to involve a rather complicated sequence of phase transitions, which may be summarized as: short range order →DO22+Ni4MO/Ni2MO→Ni3MO (orthorhombic). Hence, it is somewhat surprising to find that tne structure of the phase in Fig. 1 is solely orthorhombic Ni3MO with none of the intermediate phases present. Therefore, convergent beam electron diffraction (CBED) was used to determine the structure through symmetry arguments, and confirm the identity of this phase.
On-Line Measurement of Foil Thickness from Convergent Beam Electron Diffraction Patterns
Authors: Bentleyt J. , Lehman G. L.
Published: June 2020

Accurate values of foil thickness are required in many materials science applications, such as for measurement of defect concentrations and for x-ray microanalysis absorption corrections. Kelly et al. demonstrated that convergent beam electron diffraction (CBED) patterns can be analyzed using a simple graphical technique to give values for foil thickness with ±2% accuracy. More recently, Allen extended the treatment to make use of both maxima and minima in the CBED disks. The technique requires a knowledge of the d-spacing of the reflection, the electron wavelength, an evaluation of the deviation parameter, si, associated with the i-th fringe in the diffracted beam disk, and the assignment of a set of constants to "index" the fringes.
Analytical Electron Microscopy of Phase Growth. In The Fe-Ni-P System
Authors: Narayana C.
Published: June 2020

Solid state precipitation by classical nucleation and diffusional growth, in binary systems, requires equilibrium partitioning of the solute between the two phases. In ternary systems where one solute diffuses much faster than the other, partitioning of the slower diffusing solute species, between the two phases, is not necessary. In Fe-X-Y alloys, where X is a slow diffusing element and Y a fast diffusing element, the growth of ferrite often occurs without any significant partitioning of element X.
Vacancy Ordering in Vandadium Carbide
Authors: Yamamoto N. , Kumashiro Y.
Published: June 2020

The ordered distribution of carbon vacancies in non-stoichiometric vanadium carbides, VC1-x with NaCI type sublattice have been studied by many authors. The cubic superlattice with a doubling of lattice parameters from the rocksalt unit cell was found at a composition of V8C7. Venables, et al. have proposed a vacancy ordering with a trigonal symmetry from a composition V6C5; Billingham et al. reported ordering with a monoclinic symmetry for the same composition. These ordering structures are sensitive to small deviation of composition from V5C5, which results in the appearance of long period ordered structures.
On Line Digital Image Analysis and Processing in HREM
Authors: Boyesa E. D. , Muggridgea B. J. , Goringe M. J.
Published: June 2020

HREM has proved to be a powerful technique with wide applications in the materials sciences, but the images even from very thin crystals are not always simple to interpret reliably. Independent knowledge of the specimen thickness, microscope aberrations and operating defocus is usually required for a proper understanding or calculation of high resolution images. Offline, images must be exhaustively matched with those computed from theoretical models incorporating a range of conditions, together with optical diffractometer analysis using a laser optical bench (ODM). This process is time consuming and does not always produce satisfactory results.
Electron Microscopy in Cytology
Authors: Sjöstrand F. S.
Published: June 2020

The electron microscope as a tool for recording structural data at the molecular or supramolecular level will be discussed, particularly in connection with the important demonstration by means of electron microscopy of membranes as the most common type of supramolecular structure in cells. Structural analysis as a technique aiming at collecting information that can shed light on the function of living systems has gained tremendously by extending the range of study to molecular and intramolecular dimensions. Correlation of structure and function will be emphasized.

Electron microscopy as applied to the analysis of the circuitry of nervous centers will be discussed.

The basic problems involved in the application of electron microscopy to biochemical problems where the biochemical technique is used to analyze problems in cell physiology will be illustrated by proper examples.

Some important prospects for future application of electron microscopy in Biology will be mentioned.
Electron Microscopy in Molecular Biology
Authors: Hall Cecil E.
Published: June 2020

The visualization of organic macromolecules such as proteins, nucleic acids, viruses and virus components has reached its high degree of effectiveness owing to refinements and reliability of instruments and to the invention of methods for enhancing the structure of these materials within the electron image. The latter techniques have been most important because what can be seen depends upon the molecular and atomic character of the object as modified which is rarely evident in the pristine material. Structure may thus be displayed by the arts of positive and negative staining, shadow casting, replication and other techniques. Enhancement of contrast, which delineates bounds of isolated macromolecules has been effected progressively over the years as illustrated in Figs. 1, 2, 3 and 4 by these methods. We now look to the future wondering what other visions are waiting to be seen. The instrument designers will need to exact from the arts of fabrication the performance that theory has prescribed as well as methods for phase and interference contrast with explorations of the potentialities of very high and very low voltages. Chemistry must play an increasingly important part in future progress by providing specific stain molecules of high visibility, substrates of vanishing “noise” level and means for preservation of molecular structures that usually exist in a solvated condition.
Electron Microscopy in the Future
Authors: Fernández-Morán Humberto
Published: June 2020

At this time of remarkable progress on all fronts, successive advances can only support the presage that we are on the threshold of a renaissance in electron microscopy. Thus, having already achieved point-to-point resolution of 2-3Å, it appears feasible to strive for the ultimate goal of direct readout of molecular and pauciatomic structures. Attainment of the requisite resolution and interpretation of phase contrast images in the range of interatomic distances would permit us to obtain significant information from the object in the hitherto inaccessible region of 1-2Å. This key domain contains such a great amount of information that achievement of 1Å resolution remains the prime objective, particularly in molecular biology.
A Comparison of the Formation and Structure of the Chromatoid Body in Two Strains of Entamoeba Histolytica
Authors: Miller J. H. , Nelson E. C.
Published: June 2020

Recent studies have shown that the chromatoid bodies of the Entamoebidae are composed primarily of RNA in a crystalline array of parallel rods, each consisting of pentagonal dodecahedra stacked linearly. These studies have been confined to Entamoeba invadens, an ameba in the intestinal tract of reptiles. Therefore, it was decided to examine the formation of chromatoid bodies in two strains of E. histolytica, the human intestinal ameba. The Laredo strain, considered by some not to be a true E. histolytica because of certain biochemical and growth characteristics, was compared to a strain isolated recently by one of us (E.C.N.). This strain was obtained from a case which exhibited classical symptoms. The morphology of this organism under light microscopy was typical of the species.

Both strains were grown in Nelson's encystment medium, fixed in glutaraldehyde and osmium, embedded in Araldite and viewed in a Hitachi HU 11-A microscope.
Parameters of Successful Tissue Freezing, Studied After Substitution at – 50°C With 70% Glycol
Authors: Pease Daniel C.
Published: June 2020

Much of the water of fresh tissue can be successfully substituted with an eutectic mixture of ethylene glycol (70%) at -50°C since this removes sufficient water to stabilize macromolecular systems. Dehydration then can be completed at subzero temperatures if it is so desired. The virtue of the method is its consistent reliability. It is also possible to add 5%. glutaraldehyde to the substitution medium and so fix the tissue as it is being dehydrated. It would appear that this obviates any gross specimen damage during dehydration. Thus it makes possible an accurate assessment of damage due to gross ice crystal formation during the freezing process itself.

Kidney and pancreatic tissues in particular have been studied after subjecting them to different sorts of freezing in an effort to determine the simplest and most reliable method that is fully effective. It appears that preparations rapidly frozen in a supercooled 70%. ethylene glycol bath at dry ice temperature (-77°C) regularly are morphologically as well preserved as comparable specimens frozen at -160°C in a Freon 22 bath, or as specimens frozen as rapidly as possible at -196°C by direct contact with a massive polished brass block kept immersed in liquid nitrogen until immediately before use. Indeed, the -77°C glycol bath was superior to the -160°C Freon 22 bath in that there was never any problem with gaseous films forming protective envelopes, and it was superior to pressing specimens against the -196°C block in that there was no mechanical deformation of the tissue. The effect iveness of 70% glycol at -77°C as a quenching bath has been further demonstrated by studying liver, cartilage and brain.
Electron Microscopy of Radiation Induced Cellulose Graft Polymers
Authors: Goynes Wilton R. , Carra Jarrell H. , Blouin Florine A.
Published: June 2020

High energy irradiation produces unique reactions in cellulose. Radiation induced reactions between vinyl polymers and cellulose fibers produce vinyl-cellulose copolymers which retain a fibrous nature and exhibit desirable properties acquired from the grafted polymer. These include increased elongation, toughness, and thermoplasticity, improved abrasion, and not resistance, and decreased permanent set. The nature and extent of such improvements are dependent not only on the amount of graft polymer formed, but also on its location within the fiber. Electron microscopy has been used to investigate the location and distribution of the graft polymer. Polyacrylonitrile, polystyrene, (poly)methyl methacrylate, and polyvinyl acetate were used for grafting. It was found that distribution of the grafted polymer was dependent on such factors as type of polymer solvent used, cellulose-polymer ratio, functional groups present in the fibers, irradiation dosage used, and whether post irradiation polymerization or simultaneous polymerization was employed. Location of the graft polymer is determined microscopically by applying solvents for cellulose and for the graft polymer to the grafted fibers or their ultrathin cross sections. That portion of the section which is insoluble in either solvent is accepted to be grafted copolymer.
Transmission and Scanning Electron Microscopy of Cryptobiotic Cytoplasm
Authors: Humphreys W. J. , Hayes T. L. , Pease R. F. W.
Published: June 2020

Sections of dessicatedArtemiacysts fixed by glutaraldehyde and post fixed by osmium tetroxide (Fig. 1) reveal the protoplasmic mass of the cyst to be covered by a mildly electron dense cuticle (c) about .1μ thick. Between the cuticle and the shell (s) is an electron transparent layer about 2μ thick. The bulk of the shell, which is about 3.8μ thick, is spongy in texture with much of its volume made up of interconnecting vacuoles. This shell material is bound externally by a layer about 0.67μ thick containing many rod-shaped, electron transparent cavities oriented with their long axes roughly normal to the shell's outer surface. These cavities are not open to the shell's outer surface or to the larger cavities of the spongy layer. The surface of the shell, that abuts the extracuticular layer, is lined by an electron transparent inner layer (il) about 90mμ thick. At high magnifications an electron dense line is seen just medial to both surfaces of this inner layer. Fig. 2 shows the cytoplasm following fixation in the dessicated state. Recognizable constituents are: intercellular membranes (cm) intracellular membranes (im), yolk particles (y) and mitochondria (m). Lipid particles in close association with mitochondria were also seen in other micrographs. Figs. 3 and 4 show the fractured surface of an unfixed dessicated cyst as it is seen with the scanning electron microscope.
Freeze-Fracture Replication in the Ultrastructure of Blue-Green Algae
Authors: Leak L. V.
Published: June 2020

Electron microscopic observations of freeze-fracture replicas of Anabaena cells obtained by the procedures described by Bullivant and Ames (J. Cell Biol., 1966) indicate that the frozen cells are fractured in many different planes. This fracturing or cleaving along various planes allows one to gain a three dimensional relation of the cellular components as a result of such a manipulation. When replicas that are obtained by the freeze-fracture method are observed in the electron microscope, cross fractures of the cell wall and membranes that comprise the photosynthetic lamellae are apparent as demonstrated in Figures 1 & 2.

A large portion of the Anabaena cell is composed of undulating layers of cytoplasm that are bounded by unit membranes that comprise the photosynthetic membranes. The adjoining layers of cytoplasm are closely apposed to each other to form the photosynthetic lamellae. Occassionally the adjacent layers of cytoplasm are separated by an interspace that may vary in widths of up to several 100 mu to form intralamellar vesicles.
Aggregation Studies: MR and MA With Poxvirus
Authors: Sharp D. G. , Kim Kwang Soo
Published: June 2020

The only instrument that gives direct information about virus-cell interaction at the individual particle level is the electron microscope. The counting of virus particles sedimented from dilute suspension for electron microscopy showed first that rather few of them produce plaques. Soon it was shown that the quality factor (Q=PFU/particles) was not a constant. It changed during the repeated passages required for adaptation of a virus to growth in a new host cell. More recently changes in Q have been observed when changes are made in the state of aggregation of the virus particles. These changes, their measurement and their meaning are the substance of this paper.

Virus particles sedimented from dilute suspension fall upon a flat surface producing a pattern that shows coincidence pairs, triplets, etc., produced by chance falling together of separate particles. The number of these is small and it can be calculated. Aggregation in excess of this amount is true aggregation. It is the actual state of the virus particle population that encounters the cells of the monolayer on which plaques appear. From electron micrographs the frequency Ni of groups containing i particles is determined together with the total number of particles.
Electron Microscopy of the Hemagglutinin of Infectious Bronchitis Virus
Authors: Nazerian K. , Cunningham C. H.
Published: June 2020

Infectious bronchitis virus (IBV) does not cause hemagglutination unless modified by trypsin, or ether or selectively eluted from diethylaminoethyl (DEAE)-cellulose.

The virus in allantoic fluid is spherical averaging 110 mμ in diameter (Figure 1) and has club shaped spikes or projections on the surface. When treated with 1% trypsin for 30 minutes at 56° the virus is capable of hemagglutinating fowl erythrocytes. This treatment removes the spikes from the surface of the virus (Figure 2) and destroys an inhibitor of hemagglutination activity in allantoic fluid. It is not known whether changes on the surface of the virus are necessary or destruction or alteration of the inhibitor molecule by trypsin is adequate for induction of hemagglutination by IBV. The latter, however, is necessary since normal allantoic fluid inhibits the already induced hemagglutination activity of the virus.

Treatment of the virus with ether removes the spikes and partially disrupts the virion (Figure 3) but no rosette-shaped particles are released, although such a treatment induces the hemagglutination activity of the virus (1).
Crystalline Arrays of Foot-and-Mouth Disease Virus in Tissue Culture Cells
Authors: Breese S.S. , Graves J.H.
Published: June 2020

The formation of crystalline arrays of foot-and-mouth disease virus (FMDV) particles in swine kidney tissue culture cells has been examined in greater detail following the initial report of strain A119 in pig kidney cell line cultures, PK15. In the present experiments, FMDV strains recently isolated from field outbreaks in Argentina (A1, O2 and C3 CANEFA) were inoculated into primary swine kidney tissue cultures and samples at suitable intervals for embedding, sectioning and electron microscopy.

The three strains of FMDV were stored at -20°C as the sixth bovine kidney tissue culture passage of original tongue tissue suspension. Immediately prior to use, they were inoculated into bovine kidney cultures and 1 ml of infected cell suspension was used in each swine kidney prescription bottle. After l/2 hr incubation at 37°C, 5 to 10 ml of maintenance medium was added and the bottles stored at 37°C. At intervals of 90 min, 3, 4, 5 and 6 hr after inoculation, bottles were processed for electron microscopy. Fluids were removed and the cells gently scraped from the glass into a few ml of Sorenson’s buffer at pH 7.2. Fixation was in 1% glutaraldehyde followed by 2% osmium tetroxide, dehydration, and embedment in epon. Sections were examined in an RCA-EMU-3-G microscope.
Electron Microscopic Studies of Virus Associated With L1210 Leukemia
Authors: Chopra H. C. , Schidlovsky G. , McBride T.
Published: June 2020

Lymphocytic leukemia L1210 was orignially induced in female DBA mice by painting the skin surface with 0.2% methylcholanthrene in ethyl ether. It is continuously passed in DBA, C57bl/c and BDF mice by inoculating ascites cells intraperitoneally, intramuscularly or subcutaneously. It is commonly used for biochemical studies as well as for assays of chemotherapeutic agents.

Our electron microscopic studies demonstrated a virus with morphological characteristics peculiar to both type B and C virus particles. Cells of ascitic fluids, spleen, lymph nodes, thymus and bone marrow of leukemic mice revealed the presence of groups of intracytoplasmic A particles (Fig. 1) identical to those seen in mouse mammary tumors. Some cells also revealed intracisternal A particles identical to those in plasma cell tumors.
Recent Studies on a Murine Leukemia Virus Grown in Tissue Culture
Authors: de Tkaczevski L. Z. , de Harven E. , Friend C.
Published: June 2020

Despite extensive studies, the correlation between the morphology and pathogenicity of murine leukemia viruses (MLV) has not yet been clarified. The virus particles found in the plasma of leukemic mice belong to 2 distinct groups, 1 or 2% of them being enveloped A particles and the vast majority being of type C. It is generally believed that these 2 types of particles represent different phases in the development of the same virus. Particles of type A have been thought to be an earlier form of type C particles. One of the tissue culture lines established from Friend leukemia solid tumors has provided the material for the present study. The supernatant fluid of the line designated C-1A contains an almost pure population of A particles as illustrated in Figure 1. The ratio is, therefore, the reverse of what is unvariably observed in the plasma of leukemic mice where C particles predominate.
In Situ Electron-Microprobe Analyses of Tissue Cultures Grown on Glass
Authors: Landstrom D. K. , Johnsson-Hegyeli R. I. , Hegyeli A. F.
Published: June 2020

The electron microprobe has found several applications in medicine and biology. These were recently reviewed by Tousirnis. He and others have shown it to be useful for the localization of Ca, P, Fe, Ag, Zn, Cr, and Sn in normal and diseased tissues. The majority of these studies were conducted on histological sections, several cells thick, with the cells cut in different planes, and overlapping one another.

This paper reports on the analysis of cells grown in a horizontal monolayer. The cells are left intact, and are analyzed on the coverslip on which they are grown. L-929 fibroblasts and KB carcinoma cells were grown on 10 x 50-mm Bellco glass coverslips in Leighton tubes. The culture medium was Hanks' Basal medium of Eagle, supplemented with penicillin, streptomycin, and 10 percent calf serum. The cultures were incubated at 37 C in a horizontal position for periods up to 3 days. They were then fixed with absolute methanol for 10 seconds, washed with several changes of distilled water, and dried. The cultures were prepared for analysis by vacuum deposition of 100 A of elemental carbon.
Electron Microscope Studies on Phosphatase Activities in the Malphighian Tubules of Grasshopper
Authors: Yasuzumi G.
Published: June 2020

Activities of such phosphatases as thiamine pyrophosphatase (TPPase), glucose-6-phosphatase (G6Pase), and adenosine triphosphatase (ATPase) were observed in the Malpighian tubules of grasshopper, Atractomorpha bedeli Bolivar, which were fixed for 15 to 30 minutes in 1 per cent glutaraldehyde adjusted to pH 7.2 with Na-cacodylate buffer. Small slices of fixed specimens were incubated for 15 to 30 minutes at 37° C in the Wachstein-Meisel medium containing G6P or ATP, or in the Novikoff-Goldfischer medium containing TPP together with lead nitrate. They were postfixed for 1 hour in 1 per cent osmium teroxide buffered to pH 7.2 with Veronal-acetate buffer. Some specimens were incubated in substrate-free media as controls. Pinal reaction products of TPPase and G6Pase are.demonstrated in Figures 1 and 2 in low magnification. Localizations of the reaction products of TPPase, G6Pase and ATPase activities are depicted in Table 1.
Ultrastructural Studies of Human Erythrocytes Following Exposure to Hemolytic Agents
Authors: Minick O. T. , Jibril A. O. , Volini F. , Kent G.
Published: June 2020

Ultrastructural studies were carried out in human erythrocytes following exposure to a number of agents known to affect the cellular membrane; these included Retinol, p-chloromercuribenzoate (pCMB), Iodoacetate (IAc) and Neuraminidase.

Erythrocytes treated with retinol revealed two types of inclusions, electron lucid and electron opaque bodies (Fig. 1). The latter often protruded from the surface and were mostly associated with the membrane, while the former more often were within the cell, away from the cell membrane. That both types of bodies could be truly intracellular in location was shown by serial sections. Addition of ferritin to the incubation medium and its appearance in electron lucid bodies indicated a pinocytosis-like process as mode of formation of the latter structures (Fig. 2). The electron dense bodies, by contrast, appeared to represent membrane alterations occasionally causing surface invagination.
Unusual Intranuclear Structures in Chick Sympathetic Neurons
Authors: Masurovsky E. B. , Benitez H. H. , Murray M. R.
Published: June 2020

Recent light- and electron microscope studies concerned with the effects of D2O on the development of chick sympathetic ganglia in long-term, organized culture revealed the presence of rod-like fibrillar formations, and associated granulofibrillar bodies, in the nuclei of control and deuterated neurons. Similar fibrillar formations have been reported in the nuclei of certain mammalian CNS neurons; however, related granulofibrillar bodies have not been previously described. Both kinds of intranuclear structures are observed in cultures fixed either in veronal acetate-buffered 2%OsO4(pH 7. 4), or in 3.5% glutaraldehyde followed by post-osmication. Thin sections from such Epon-embedded cultures were stained with ethanolic uranyl acetate and basic lead citrate for viewing in the electron microscope.