bluuebunny/crossref_metadata_2025 huggingface dataset:
Removing Substrate Background in TEM Microanalysis
Authors: Russ John C. , Barbi Nicholas C.
Published: June 2020

The rapid growth of interest in attaching energy-dispersive x-ray analysis systems to transmission electron microscopes has centered largely on microanalysis of biological specimens. These are frequently either embedded in plastic or supported by an organic film, which is of great importance as regards stability under the beam since it provides thermal and electrical conductivity from the specimen to the grid.

Unfortunately, the supporting medium also produces continuum x-radiation or Bremsstrahlung, which is added to the x-ray spectrum from the sample. It is not difficult to separate the characteristic peaks from the elements in the specimen from the total continuum background, but sometimes it is also necessary to separate the continuum due to the sample from that due to the support. For instance, it is possible to compute relative elemental concentrations in the sample, without standards, based on the relative net characteristic elemental intensities without regard to background; but to calculate absolute concentration, it is necessary to use the background signal itself as a measure of the total excited specimen mass.
Mammalian Bone Marrow Acetylcholinesterase
Authors: Keyhani Ezzatollah
Published: June 2020

Acetylcholinesterase (EC 3.1.1.7) (ACHE) has been localized at cholinergic junctions both in the central nervous system and at the periphery and it functions in neurotransmission. ACHE was also found in other tissues without involvement in neurotransmission, but exhibiting the common property of transporting water and ions. This communication describes intracellular ACHE in mammalian bone marrow and its secretion into the extracellular medium.
Morphometric Analysis of Portal Hepatocytes from Rats Treated with Compound 48/80
Authors: Dimlich R.V.W. , Cardell R.R.
Published: June 2020

Compound 48/80, a mast cell degranulating agent, produces marked hypotension in the rat. Thirty minutes after intravenous treatment with compound 48/80 there is a significant increase in blood-glucose with a concommitant decrease in hepatic glycogen similar to that observed in shock-like states. Electron microscopic observations of hepatocytes from rats treated with 48/80 have shown an apparent decrease in hepatic glycogen and increase in smooth endoplasmic reticulum (SER). Mitochondria in these cells seemed to contain fewer matrix granules. The present analysis was performed to quantify these observations. Since light microscopic observations of tissue from these rats revealed an apparent greater depletion of glycogen in the portal areas (unpublished observation), hepatic portal cells were analyzed in this initial study.
Techniques for Obtaining High Resolution Information about Periodic Arrays of Biological Macromolecules in the Electron Microscope
Authors: Hayward S. B.
Published: June 2020

In the past six years considerable effort has been expended in EM structure analysis of periodic arrays of biological macromolecules. Although sparked by the success of the moderately high resolution structure analysis of purple membrane J most of this work has been limited in resolution to anywhere from 30 to 15 A. Although there is much to learn out to this range of resolution, especially in three dimensions, there is a wealth of structural information awaiting us beyond it. Our ultimate goal must, of course, be information in the range of 3 A, which for proteins is enough to allow us to trace the path of the polypeptide chain. In fact, much of this information is accessible by electron microscopy, providing that the periodic arrays are ordered to this extent. However, great care must be taken to optimize all aspects of microscopy and image processing in order for structural information of a resolution close to the instrumental limitation to be obtained. Following are some of the more important factors which will determine success or failure of an attempt at high resolution imaging, in this case assumed to be of an untilted specimen. While some of these factors have been known for years by workers in the field of high resolution electron microscopy, others are problems unique to imaging biological macromolecular arrays. The recent solution of some of these problems involves the use of probability distributions to describe image phases.
Dynamical Structure Factors for Bent Organic Crystals
Authors: Moss Barbara , Dorset Douglas L.
Published: June 2020

The success of quantitative crystal structure determination from electron diffraction data requires a valid analysis of the observed intensities. Traditional X-ray crystallographic techniques rely on the kinematic scattering model. However, some organic microcrystals exhibit significant dynamical scattering from extremely thin specimens and crystal bending further complicates the observed scattering intensity. While each of these data perturbations has been studied separately, a combined calculation is important to indicate the validity of separate treatments. Solution-grown hexatriacontane, C36 H74, a long-chain hydrocarbon with the long axis (c=95.14Å) parallel to the electron beam direction exhibits significant dynamical and bend effects. It is thus a particularly difficult structure to analyse from hkO electron diffraction data. Multislice dynamical calculations for a curved crystal lattice of this material are considered.
Analysis of Adhesion Plaque Structure and Function in the Mechanism of Transformation by Rous Sarcoma Virus
Authors: Rohrschneider L.R. , Rosok M.J. , Gentry L.E.
Published: June 2020

Rous sarcoma virus (RSV) was originally isolated from a fibrosarcoma of a chicken. This virus also will efficiently infect and transform all avian cells in culture as well as most mammalian cells. The mechanism of transformation by RSV is therefore universal and this system offers an excellent opportunity to investigate the mechanism of neoplastic transformation.
Study of the Molecular Architecture of Keratin Filaments by Electron Microscopy
Authors: Aebi U. , Rew P. , Sun T.-T.
Published: June 2020

Various types of intermediate-sized (10-nm) filaments have been found and described in many different cell types during the past few years. Despite the differences in the chemical composition among the different types of filaments, they all yield common structural features: they are usually up to several microns long and have a diameter of 7 to 10 nm; there is evidence that they are made of several 2 to 3.5 nm wide protofilaments which are helically wound around each other; the secondary structure of the polypeptides constituting the filaments is rich in ∞-helix. However a detailed description of their structural organization is lacking to date.
Effect of Calcium on the Growth and Differentiation of Cultured Rat Esophageal Epithelial Cells
Authors: Gunning W.T. , Marino M.R. , Babcock M.S. , Stoner G.D.
Published: June 2020

The role of calcium in modulating cellular replication and differentiation has been described for various cell types. In the present study, the effects of Ca++ on the growth and differentiation of cultured rat esophageal epithelial cells was investigated.

Epithelial cells were isolated from esophagi taken from 8 week-old male CDF rats by the enzymatic dissociation method of Kaighn. The cells were cultured in PFMR-4 medium supplemented with 0.25 mg/ml dialyzed fetal bovine serum, 5 ng/ml epidermal growth factor, 10-6 M hydrocortisone 10-6 M phosphoethanolamine, 10-6 M ethanolamine, 5 pg/ml insulin, 5 ng/ml transferrin, 10 ng/ml cholera toxin and 50 ng/ml garamycin at 36.5°C in a humidified atmosphere of 3% CO2 in air. At weekly intervals, the cells were subcultured with a solution containing 1% polyvinylpyrrolidone, 0.01% EGTA, and 0.05% trypsin. After various passages, the replication rate of the cells in PFMR-4 medium containing from 10-6 M to 10-3 M Ca++ was determined using a clonal growth assay.
Ruthenium Red Enhancement of Surface Complex Components of Isolated and in Situ Cardiac Myocytes of Syrian Hamsters
Authors: Caceci T. , Orenstein J.M. , Bloom S.
Published: June 2020

Fibrils of widely differing sizes have been reported in association with the sarcolemma of cardiac myocytes in situ. Elements of this surface complex include 25-50 nm-thick striated collagen fibrils, 8-10 nm-thick unbanded fibrils (UFs), and fine 4-6 nm-thick glycocalyceal fibrils. In addition, glycosaminoglycans (GAGs) have been found associated with the surface complex. SEM examination of the surface of mechanically disaggregated myocytes revealed longitudinally-oriented cable-like fibers bridging the Z-band depressions. These cables are believed to correspond to the UFs seen in TEM preparations. We are currently studying the surface complex of isolated cardiac myocytes in an attempt to clarify its role in myocardial mechanics. In order to define the elements of the surface complex of these cells, and to examine their relationships to one another, we have applied the ruthenium red (RR) method of Luft.
Radioautographic Analysis of the Intralobular and Intracellular Distribution of Newly Formed Hepatic Glycogen After Injection of 3H-Galactose
Authors: Michaels J. E. , Hung J. T. , Cardell R. R.
Published: June 2020

In normal animals glycogen levels in the liver are closely related to blood sugar levels. High levels of glucose in the blood stimulate uptake of glucose by liver hepatocytes and synthesis of glycogen whereas low blood glucose levels result in breakdown of glycogen and release of glucose into the blood. After adrenalectomy and overnight fasting, liver glycogen levels in the rat are reduced to about 0.03%. The adrenalectomized rat is easily stimulated to form new glycogen by injection of a glucocorticoid hormone such as dexamethasone (DEX).
Ultrastructural Correlations between Clonal Human Tumor Colonies and in Vivo Neoplasms
Authors: Murphy M.J. , Price R.R. , Sloman J.C.
Published: June 2020

The in vitro human tumor cloning assay originally described by Salmon and Hamburger has been applied recently to the investigation of differential anti-tumor drug sensitivities over a broad range of human neoplasms. A major problem in the acceptance of this technique has been the question of the relationship between the cultured cells and the original patient tumor, i.e., whether the colonies that develop derive from the neoplasm or from some other cell type within the initial cell population. A study of the ultrastructural morphology of the cultured cells vs. patient tumor has therefore been undertaken to resolve this question. Direct correlation was assured by division of a common tumor mass at surgical resection, one biopsy being fixed for TEM studies, the second being rapidly transported to the laboratory for culture.
Ultrastructural Contributions to the Histogenesis of Pleomorphic Adenoma
Authors: Dardick I. , Nostrand A.W.P. van , Jeans Diane , Rippstein P. , Edwards V.
Published: June 2020

Hospital, Ottawa, Canada and ^Hospital for Sick Children, Toronto, Canada. Survey-type electron micrographs correlated with semithin plastic sections (Fig. 2) were used in an ultrastructural study of 24 cases of salivary gland pleomorphic adenoma in order to assess tumor cell types and their organization in cellular regions and the gradual alterations occurring with the development of myxoid areas. Such micrographs confirm the presence of two principal cell types with smaller numbers of highly organized luminal epithelial cells forming duct- or acinar-like structures and more numerous, angular, mosaically or loosely arranged tumor cells surrounding luminal type cells. As is evident in Figure 1, darker staining, angular tumor cells just external to duct luminal cells have a specific and intimate association with luminal cells through cell processes and well developed desmosomes. Despite the lack of classical features of myoepithelial cells, the organizational arrangement of the two cell types and the distinctly different cytologic features of tumor cells external to luminal epithelial cells suggests that the former cell type represents myoepithelial cells modified as a result of neoplastic induction (Figs. 1 and 2).
Cytochemical Observations on Human Breast Tumor Plasma Membranes
Authors: Lucid S.W. , Wen K.J. , Wen J.W. , Lerner M.P. , Nordquist R.E.
Published: June 2020

In order to survive in a hostile environment, tumor cells evolve a variety of defense mechanisms to counter the rejection efforts of the host. Recent data suggest that neoplastic cells release membrane fragments which resemble the intact plasma membrane. These fragments may block host cytotoxic activities and effect an active tumor excape mechanism. We now report that cultured human breast tumor cells release large amounts of membrane vesicles bearing micromaps of the cells' plasma membrane.
Glycosomes in Squamous Cell Carcinoma of the Lung
Authors: Rybicka Krystyna , Bedrossian Carlos
Published: June 2020

Alterations in glycogen content are a common feature of neoplastic cells, although no structural pattern has been thus far recognized. Cellular glycogen occurs in glycosomes; organelles composed of glycogen and proteins which include enzymes involved in glycogen metabolism. U1trastructural identification of glycosomes suggests that the study of these organelles may provide a better understanding of the function of glycogen in the cell and of the alterations associated with neoplastic transformation. Two groups of glycosomes have been recognized in cardiac cells: 1 ) acid-resistant single glycosomes which are bound to other structures and 2 ) acidlabile aggregates of glycosomes deposited free in the cytoplasm. We have sought to determine whether these two groups of glycosomes occur in squamous cell carcinoma of the lung and to identify organelles associated with glycosomes.
The Response of Testes Cells to Low Level, Single dose Helium Particle Irradiation
Authors: Philpott D.E. , Sapp W. , Williams C. , Stevenson J. , Black S. , Corbett R. , Miquel J.
Published: June 2020

Spermatogonial stem-cell survival after irradiation injury has been studied in rodents by histological counts of surviving cells. Many studies, including previous work from our laboratory, show that the spermatogonial population demonstrates a heterogeneous response to irradiation. The spermatogonia increase in radio-sensitivity as differentiation proceeds through the sequence As - Apr - A1 - A2 - A3 - A4 - In - B. The stem (As) cell is the most resistant and the B cell is the most sensitive. The purpose of this work is to investigate the response of spermatogonial cell to low doses (less than 10 0 rads) of helium particle irradiation.
Cytoskeleton and Extracellular Matrix Interactions During Sertoli Cell-Cell Adhesion in Vitro
Authors: Decker Glenn L. , Carson Daniel , Lennarz William J.
Published: June 2020

The cytoskeletal components of Sertoli cells appear to play an important role both in the maintenance of elaborate basolateral septate junctions (presumptive blood-testes barrier) and in the development and movement of germ cells into the semeniferous tubule lumen. Additionally, Sertoli cells contain numerous endocytotic vesicles, subjacent to the basal lamina, which may be involved in delivery of serum components to germ cells during maturation. Until now ultrastructural studies have been confined to semeniferous tubules or primary cultures of Sertoli cells. We have initiated studies to visualize the cytoskeleton and extracellular matrix of an established Sertoli cell line.
Freeze-Fracture Demonstration of a Suture in the Free Sporozoite of Plasmodium Berghei
Authors: Meszoely Charles A.M. , Erbe Eric F. , Steere Russell L. , Pacheco Nancy D. , Beaudoin Richard L.
Published: June 2020

The ANKA strain of Plasmodium berghei was maintained in Anopheles Stephensi mosquitoes. Free sporozoites were obtained from a homogenized suspension of mosquito thoraces and heads. They were separated from cell components on a discontinuous gradient, concentrated by centrifugation, fixed in 2% glutaraldehyde, and cryoprotected in a solution containing approximately 12.5% glycerol by volume, and 12.5% sucrose by weight in a 0.2 molar sodium phosphate buffer. The sporozoite preparation was freeze-etched for 1 minute in a modified Denton DFE-2 freeze-etch module. The replicas were photographed in stereo (10 tilt between micrograph pairs) with a JEM-100B transmission electron microscope equipped with a 60° top entry goniometer stage.
Advances in Microprobe Analysis Applied to Muscle, Nerve and Gland
Authors: Hutchinson T. E. , Johnson D. E. , Lee A. C. , Wang E. Y.
Published: June 2020

Microprobe analysis of biological tissue is now in the end phase of transition from instrumental and technique development to applications pertinent to questions of physiological relevance. The promise,implicit in early investigative efforts, is being fulfilled to an extent much greater than many had predicted. It would thus seem appropriate to briefly report studies exemplifying this, ∿. In general, the distributions of ions in tissue in a preselected physiological state produced by variations in the external environment is of importance in elucidating the mechanisms of exchange and regulation of these ions.
Periodic Extension in Optical Diffraction Analysis
Authors: Gronsky R. , Murty C.S.
Published: June 2020

Although the more traditional applications of optical diffractograms in high resolution electron microscopy are related to determining instrumental performance, a significant advantage can also be achieved with this technique in the analysis of fine microstructural detail. Optical microdiffraction utilizes a field-limiting aperture in the optical bench system to selectively obtain the diffraction spectrum of specific segments of high resolution negatives, with a considerable increase in spatial resolution. Unfortunately the diffraction effects from the sampling aperture itself often interfere with the interpretation of results
Dislocation Structures in Deformed Tin Single Crystals
Authors: Qiao G.W.
Published: June 2020

Although β-tin is a familiar metal with tetragonal structure, its dislocation structures in bulk specimens after plastic deformation or irradiation have not been reported with observations by TEM probably because of difficulties in preparing specimens and the relatively high mobility of dislocations under electron beam illumination at room temperature (T/Tm~0.7). It proved possible to prepare specimens of β-tin for TEM observation using low temperature, double-jet electro-polishing techniques using 8% perchloric acid in methanol mixture at -30 °C under 80 volts and a typical current density of 0.7 Acm-2.
Effects of Incoherent Dispersoids. Temperature, and Deformation Mode on Dislocation-Substructure Development in Ti-8A1 and Ti-10Al Alloys
Authors: O’Neal J. E. , Sastry S. M. L.
Published: June 2020

In titanium-aluminum alloys with aluminum concentrations between 10 and 20 at.%, the ordered and coherent α2 phase (based on the composition Ti3Al and having an ordered DO19 lattice structure) precipitates upon aging. Although a significant loss of ductility generally accompanies the precipitation strengthening in these alloys, it is possible to improve the roomtemperature ductility of an α2-precipitation-strengthened Ti-Al alloy by reducing the grain size and incorporating incoherent dispersoids into the lattice.
Analytical Electron Microscopy of Extraterrestrial Stratospheric Particles
Authors: Isaacs A.M. , Mackinnon I.D.R. , McKay D.S.
Published: June 2020

A NASA program to collect extraterrestrial particles from the stratosphere has resulted in a growing understanding of fine grained materials in the earth's upper atmosphere. These particles, if extraterrestrial, are refered to as interplanetary or cosmic dust. Typically they range in size from 1.0 to 50.0 urn in diameter. The cosmic dust collected within our atmosphere has several postulated origins. These origins include disaggregated comets, asteroid collisions, meteorite-planetary impacts, residual material from the formation of the solar system and interstellar dust which may be pre-solar in age. It is of interest to understand the mineralogy of these materials since this information is of direct relevance to understanding the history of the solar system. A variety of techniques have been employed in the study of several hundred particles collected thus far. Selected results from our electron microscope investigations are reported here.
Microstructure of Evaporated Dielectric Films
Authors: Kenik E. A. , Lowrey W. H. , Houston J. T.
Published: June 2020

Dielectric films are used as optical coatings in a variety of mirror and lens based optical systems. These materials are generally thin films formed by either evaporation or sputter deposition whose optical properties, perfection and damage resistance are influenced by changes in the deposition process. The present study is aimed at understanding the microstructural and microchemical state of several types of dielectric films and correlation of that state with the observed properties. Thin films of ZnS, ZnSe and ThF4 prepared in either of two different fashions have been examined: (1) free-standing films deposited on alkali halides and removed by dissolving the substrate, or (2) films deposited on thin silicon single crystals and then ion milled (from the Si side) to electron transparency. Conventional transmission electron microscopy was performed on a JEOL 120C microscope.
Analytical Electron Microscopy of Neutron-Irradiated Reactor Alloys
Authors: Thomas L. E.
Published: June 2020

Exposure to the high neutron fluxes and temperatures from 400 to 650°C in the core region of a fast breeder reactor profoundly alters the microstructure and properties of structural steels and superalloys. The development of irradiation-induced voids, dislocations and precipitates, as well as segregation of alloying elements on a microscopic scale has been related to macroscopic swelling, creep, hardening and embrittlement which occur during prolonged exposures in reactor. Microanalytical studies using TEM/STEM methods, primarily energy dispersive X-ray (EDX) microanalysis, have greatly aided our understanding of alloy behavior under irradiation.
Radiation Damage in Ceramics
Authors: Mitchell T. E. , Pascucci M. R. , Youngman R. A.
Published: June 2020

1. Introduction. Studies of radiation damage in ceramics are of interest not only from a fundamental point of view but also because it is important to understand the behavior of ceramics in various practical radiation enyironments- fission and fusion reactors, nuclear waste storage media, ion-implantation devices, outer space, etc. A great deal of work has been done on the spectroscopy of point defects and small defect clusters in ceramics, but relatively little has been performed on defect agglomeration using transmission electron microscopy (TEM) in the same kind of detail that has been so successful in metals. This article will assess our present understanding of radiation damage in ceramics with illustrations using results obtained from the authors' work.
A Tem Study of Intergranular Cracking in WC-Co
Authors: Jayaram V.
Published: June 2020

While WC-Co based alloys are extensively used in industry, there is still uncertainty as to the microscopic mechanisms that control deformation and fracture in the hard carbide phase. In this paper, observations are reported of intergranular cracking between WC grains in a fine-grained WC-Co composite. The onset of cracking is related to the operative slip systems in neighbouring grains, the grain boundary plane and the relative orientation of the two grains. Bright field imaging and micro-diffraction are used to determine these parameters.
Fine Structure of Track-Plated Au-Cu Alloy
Authors: Johnson K. A. , Staudhammer K. P.
Published: June 2020

Track plated materials offer unique mechanical properties over conventional plating techniques. The burnishing process, i.e., mechanical rubbing of the deposit during electrodeposition, produces continuous nucleation of new grains during deposition which effectively prevents large columnar grains and macroporosity. In addition, track plating produces a uniform subgrain and substructure. Earlier work was done on Au 3.6 to 33.2 at.% Cu. This work using other plating variables has resulted in significantly different microstructures.
Preparation of Transverse Sections of Oxidized Ni and Fe-Cr Alloys
Authors: Tinker M. T. , Labun P. A.
Published: June 2020

In the study of oxidation, the microstructure and microchemistry of oxide scales can readily be examined via transverse sections. This necessitates the preparation of transversely sectioned specimens that possess electron transparent oxide scales. Another method for transverse sectioning of oxidized nickel has been previously reported, These specimens were produced from techniques similar to those of Tuck, Sheng and Marcus and Katz and Evans. In this method, two oxidized metal strips are placed adjacent to each other and the strips encased within an epoxy-resin setting. The specimens are then transversely sectioned and ion-beam thinned. Unfortunately, this technique results in inadequate success rates, mostly because of the relatively fast ion-thinning of the epoxy resin.
Detachment Deformation of Polyethylene Single Crystals
Authors: Alward D.B. , Thomas E.L.
Published: June 2020

Over the years there have been a great deal of studies on polyethylene single crystals. The experimental and theoretical work has focussed on not only the structure of the crystals, but also on the way in which they deform, in an effort to understand the structure and behavior of bulk samples. Many early studies dealt with the question of degree of adjacency of fold re-entry by plastically deforming the crystals in the plane of the crystals (perpendicular to the chain axis) on a polyethylene terephthalate (PET) substrate. The number and nature of fibrils pulled across the crack were observed as a function of crack position in the crystal and orientation to the stress. This work deals with a similar but different technique to strain the crystals, called detachment deformation.
Electron Microscopic Observation of the Longitudinal Organization of Poly (p-Phenylene Terephthalamide) Fibers
Authors: Li-Sheng Li , Allard L.F. , Bigelow W.C.
Published: June 2020

The aromatic polyamides form a class of fibers having mechanical properties which are much better than those of aliphatic polyamides. Currently, the accepted morphology of these fibers as proposed by M.G. Dobb, et al. is a radial arrangement of pleated sheets, with the plane of the pleats parallel to the axis of the fiber. We have recently obtained evidence which supports a different morphology of this type of fiber, using ultramicrotomy and ion-thinning techniques to prepare specimens for transmission and scanning electron microscopy.
Symmetries and Extinction Rules in CBED
Authors: Ishizuka K.
Published: June 2020

The technique of convergent-beam electron diffraction (CBED) has been established. However there is a distinct discrepancy concerning the CBED pattern symmetries associated with translation symmetries parallel to the incident beam direction: Buxton et al. assumed no detectable effects of translation components, while Goodman predicted no associated symmetries. In this report a procedure used by Gjønnes & Moodie1 to obtain dynamical extinction rules will be extended in order to derive the CBED pattern symmetries as well as the dynamical extinction rules.
An Overview of Digital Image Processing and Recognition (Invited Paper)
Authors: Gonzalez R. C.
Published: June 2020

Interest in digital image processing techniques dates back to the early 1920's, when digitized pictures of world news events were first transmitted by submarine cable between New York and London. Applications of digital image processing concepts, however, did not become widespread until the middle 1960's, when third-generation digital computers began to offer the speed and storage capabilities required for practical implementation of image processing algorithms. Since then, this area has experienced vigorous growth, having been a subject of interdisciplinary research in fields ranging from engineering and computer science to biology, chemistry, and medicine.
Crystallization of Cu-Zr and Cu-TI Metallic Glasses
Authors: Marshall A. F. , Lee Y. S. , Walmsley R. G.
Published: June 2020

Studies of the crystallization of metallic glasses provide information concerning structure and stability of the amorphous state as well as data on metastable transitions, crystallization kinetics, and equilibrium phases. AEM techniques can prove invaluable in elucidating details of the crystallization sequence. Results are shown for Cu-Zr and Cu-Ti alloys prepared by the vapor quench technique of planar magnetron sputter deposition.
The Habit Plate Shift and the Morphology of ∝" Nitride Precipitate in ∝-Fe*
Authors: Shih Y. C. , Morris J. W.
Published: June 2020

A new phase which precipitates from a parent matrix has a size and shape which reflects its difference from parent phase. If the lattice mismatch is significant, the elastic strain energy is more important than the surface energy in determining the morphology and the preferred habit plane. The preferred habit of a tetragonal inclusion in a cubic matrix has been predicted by minimizing the elastic strain energy as from the Ktachaturyan linear elastic formula.
Fine Structure of the Crayfish Sinus Gland
Authors: Bunt Ann Heffington , Ashby Ebert A.
Published: June 2020

The sinus gland of the crayfish, Procambarus clarkii, is located on the dorsum of the eyestalk, just beneath the exoskeleton and adjacent to the medullae interna and externa optic ganglia. It functions to secrete a variety of proteinaceous hormones, including the erythrophore concentrating hormone, melanophore dispersing hormone, molt inhibiting hormone, diabetogenic hormone, distal retinal pigment hormone, and ovary inhibiting hormone.

The gland is composed of numerous neurosecretory axon terminals clustered about a branching blood sinus. The neurosecretory axons arise from cells lying some distance away from the sinus gland, in the medulla terminal is X-organ, the brain, and possibly the thoracic ganglion. The hormones are manufactured in the perikarya of these cells and transported through the axons to their terminals in the sinus gland for storage and release into the blood sinus.

Small, electron dense spherules within the axons contain the hormone secretory product. These neurosecretory granules are very similar in morphology to those reported in the sinus glands of the dwarf crayfish, Cambarellus shufeldti, the land crab, Gecarcinus lateralis, and the Mediterranean isopod, Sguilla mantis. The sinus glands of each of these crustaceans contain two size ranges of neurosecretory granules: 1500-2000A and 500-900A.
Origin of Plasma Cells in the Thymus
Authors: Trillo A. , Gonzalez A.
Published: June 2020

The origin of plasma cells in the thymus as well as in the lymphoid organs and sites of inflammation is still being discussed. Moore and Schoenberg believed that in experimentally induced inflammation they developed from both small and medium lymphocytes. Nossal and Keuning concluded that plasma cells originated from a primitive lymphocyte in lymph nodes. In the thymus they are absent during the first weeks of age, but from the sixth week on they are easily recognized even under the light microscope, and their number appears to increase during the following weeks.

In the present work we examined the corticomedullary junction area of the thymus in albino rats at progressive ages, starting at an hour after birth, and then at weekly intervals until the twelfth week. The appearance of the thymus during the first weeks is rather simple; it consists mainly of islets of undifferentiated epithelial reticular cells, surrounded by small and medium sized lymphocytes.
The Mechanism of Erythroblast Denucleation
Authors: Simpson Charles F. , Carlisle J. W. , Kling J. M.
Published: June 2020

It is not known whether loss of nuclei from erythroblasts occurs by extrusion or by karyolysis, or both. In this study, blood from anemic dogs was utilized. Dogs were anemic as a result of severe parasitism with a hematozoic parasite, Babesia canis, or were made anemic by treating them with phenyl hydrazine hydrochloride.

The mechanism of denucleation was the same in both types of anemia investigated. It was found that extrusion was the principal mechanism of denucleation from the erythroblast. However, probably karyolysis also occurred occasionally, prior to extrusion.
Electron Microscopic Study of the Nodal Tissue of Rat Heart
Authors: Baba N.
Published: June 2020

The nodal tissue of rat heart was examined following perfusion of glutaraldehyde through the coronary bed. The sinoatrial node cells are characterized by rather pale-appearing cytoplasm because myofibrils are few and scattered irregularly. The cytoplasm in addition contains some glycogen granules which are most abundant in the periphery of the cells. There are many smooth-surfaced tubular structures which have no topographical relationship to myofibrils as seen in ventricular myocytes. Many of these structures are present adjacent to cell membranes. The rough-surfaced endoplasmic reticulum is poorly developed. The cells are often connected by desmosomes. Occasionally there are cytoplasmic processes extending into the surrounding stroma, where moderate electron density is seen at the plasma membranes.

The cells of the atrioventricular node are much richer in myofibrils and, more particularly, in glycogen granules than are the cells of the sinoatrial node. The glycogen granules are scattered throughout the cytoplasm. There are fewer vesicular structures than in the cells of the sinoatrial node, but the rough-surfaced endoplasmic reticulum is very prominent. The cells are interdigitated and are connected by many desmosomes. In addition there are areas of increased electron density at the basal plasma membranes which appear connected with Z-line of myofibrils.
Intercellular Space of the Ovarian Follicles of the Rat During the Estrous Cycle
Authors: Baccarini I. M. , Glaczenski S. S.
Published: June 2020

Vaginal smears were taken daily from inbred Wistar-Furth rats to determine the stage of the estrous cycle. A total of 27 animals were sacrificed by over-anesthesia with ether and the ovaries removed surgically. In each case one ovary was used for electron microscopy and the other for histochemical studies.

The ovary for electron microscopy was placed immediately into cold 3% phosphate-buffered glutaraldehyde for 2 hours and then into 1% phosphate buffered osmic acid for 2-3 hours. The tissue was embedded in Durcupan ACM(Fluka). The sections were double stained with 50% alcoholic uranyl acetate solution and with lead citrate. The second ovary for histochemical studies was divided in half. One half was fixed in cold acetone for estimated alkaline phosphatase. The remaining tissue was fixed in 10% neutral formalin and stained with hematoxylin and eosin, PAS, Alcian blue, Gomori's trichrome, Gomori's aldehyde fuchsin for elastic tissue, and Wilder's reticulum. Follicles in various stages of development were studied. The intercellular space around the oocyte of the primordial follicle contains reticulum fibers. Bands of collagen fibers are seen between the oocyte and the single layer of cells (Figure 1). Between the basement membrane of the granulosa and theca cells in the secondary, tertiary, and graafian follicles, fibroblast-like cells with dilated cisterns are found. Amorphous material is present in the intercellular space (Figure 2).
The Fine Structure of Brunner’s Glands in the Rabbit
Authors: Leeson C. R. , Leeson T. S.
Published: June 2020

In most species, the duodenal glands of Brunner are composed of secretory cells which are mucous in character. In the rabbit the glands appear unique in that they possess two morphologically distinct cell types, mucous and serous. The glands are composed of coiled tubules which occasionally branch. The tubules are arranged in aggregates within the submucosa and they extend through the muscularis mucosa to terminate in the bases of the intestinal glands. With the light microscope, the two cell types can be differentiated clearly. Most cells are mucous in type, possess basally situated nuclei, and exhibit an apical cytoplasm which appears foamy due to the presence of crowded, pale-staining, secretory granules (Figure 1). Serous cells are present in small aggregates at the blind endings of the tubules. In hematoxylin and eosin preparations they appear densely stained, and each cell is characterized by the presence of a central nucleus, basal basophilia and an apical cytoplasm which contains discrete secretory granules.
Electron Microscopic Evidence for Membrane Bound Structures in Plant Vacuoles
Authors: Thomson W. W.
Published: June 2020

To date, most electron microscope studies of mature plant tissue have shown the vacuole to be generally devoid of internal structure except for irregular aggregates of electron dense granular material. However, after gluturaldehyde-osmium fixation, membrane bound structures are frequently observed in the vacuoles of the mesophyll cells of the xerophytic plant,Tamarix(Fig. 1). These structures are generally ovoid in shape and range in length from .5 to 1.6 μ.

Some of the membrane bound, vacuolar inclusions are bounded by two membranes which are often tightly opposed (Fig. 2, arrow). Other inclusions are bounded by a single tripartate membrane (Fig. 3). The internal organization of the inclusions consists of tubules surrounded by an electron-translucent matrix (Fig. 2 & 3). The tubules measure about 350 A in diameter and frequently extend in arrays parallel to the bounding membrane. Occasionally vesicles about 1000 A in diameter are also observed in the inclusions (Fig. 1).
Further Observations on the Virus of Epizootic Diarrhea of Infant Mice. An Electron Microscopic Study
Authors: Banfield W. G. , Kasnic G. , Blackwell J. H.
Published: June 2020

An ultrastructural study of the intestinal epithelium of mice infected with the agent of epizootic diarrhea of infant mice (EDIM virus) was first performed by Adams and Kraft. We have extended their observations and have found developmental forms of the virus and associated structures not reported by them.

Three-day-old NLM strain mice were infected with EDIM virus and killed 48 to 168 hours later. Specimens of bowel were fixed in glutaraldehyde, post fixed in osmium tetroxide and embedded in epon. Sections were stained with uranyl magnesium acetate followed by lead citrate and examined in an updated RCA EMU-3F electron microscope.

The cells containing virus particles (infected) are at the tips of the villi and occur throughout the intestine from duodenum through colon. All developmental forms of the virus are present from 48 to 168 hours after infection. Figure 1 is of cells without virus particles and figure 2 is of an infected cell. The nucleus and cytoplasm of the infected cells appear clearer than the cells without virus particles.
Comparison of RE Virus (Strain T) With the Visceral Lymphomatosis Agent
Authors: Zeigel R. F. , Theilen G. H. , Sarma P.
Published: June 2020

Theilen, Zeigel and Twiehaus, '66 and Zeigel, Theilen and Twiehaus, '66 reported biological and morphological observations on a virus which was originally derived from adult turkeys and which produced reticuloendotheliosis after inoculation into chicks, turkey poults, and Japanese quail. These publications indicated differences between the RE virus and the agent of visceral lymphomatosis. Because of the difficulty in obtaining absolutely R I F free embryos and chicks for experimental purposes, it was fortuitous that the early studies were not confused by contamination of the RE virus stock. Ultimately, during the final phases of the studies, some cultures utilized for R I F and C O F A L, tests became doubly infected. It is the purpose of this note to present further observations on the characteristics of the immature developing RE virus (budding forms) and to show the RE virus and the R I F agent, simultaneously, in the contaminated cultures.
Surface Structure of Nucleated Animal Cells: Carbon Replicas
Authors: Glaeser Robert M. , Scott Thea B.
Published: June 2020

The carbon-replica technique can be used to obtain information about cell-surface structure that cannot ordinarily be obtained by thin-section techniques. Mammalian erythrocytes have been studied by the replica technique and they appear to be characterized by a pebbly or “plaqued“ surface texture. The characteristic “particle” diameter is about 200 Å to 400 Å. We have now extended our observations on cell-surface structure to chicken and frog erythrocytes, which possess a broad range of cellular functions, and to normal rat lymphocytes and mouse ascites tumor cells, which are capable of cell division. In these experiments fresh cells were washed in Eagle's Minimum Essential Medium Salt Solution (for suspension cultures) and one volume of a 10% cell suspension was added to one volume of 2% OsO4 or 5% gluteraldehyde in 0.067 M phosphate buffer, pH 7.3. Carbon replicas were obtained by a technique similar to that employed by Glaeser et al. Figure 1 shows an electron micrograph of a carbon replica made from a chicken erythrocyte, and Figure 2 shows an enlarged portion of the same cell.
A Method for Electron Microscopic Study of Tissue Culture Cell Monolayers Grown in Tubes
Authors: Stephens R. , Schidlovsky G. , Kuzmic S. , Gaudreau P.
Published: June 2020

The usual method of scraping or trypsinization to detach tissue culture cell sheets from their glass substrate for further pelletization and processing for electron microscopy introduces objectionable morphological alterations. It is also impossible under these conditions to study a particular area or individual cell which have been preselected by light microscopy in the living state.

Several schemes which obviate centrifugation and allow the embedding of nondetached tissue culture cells have been proposed. However, they all preserve only a small part of the cell sheet and make use of inverted gelatin capsules which are in this case difficult to handle.

We have evolved and used over a period of several years a technique which allows the embedding of a complete cell sheet growing at the inner surface of a tissue culture roller tube. Observation of the same cell by light microscopy in the living and embedded states followed by electron microscopy is performed conveniently.
Autoradiographic Location of Protein Synthesized by Liver Slices
Authors: Ashley Charles A. , Peters Theodore
Published: June 2020

The location, migration, and secretory pathways followed by proteins, newly synthesized by the liver, were determined by electron microscopic autoradiography. Small (3x4x0.5 mm) slices of liver from fasted rats were incubated for 2 minutes in medium (0.1 ml per slice)containing H3-4,5-L-leucine and then transferred to medium with unlabeled leucine for further incubation. Total incubation times were 2,4,10,25,40 and 75 minutes. Control slices were incubated in medium containing labeled leucine and puromycin. Slices were fixed in 4% formaldehyde (prepared from paraformaldehyde), post-fixed in osmium tetroxide and embedded on end in Epon. Autoradiographs were prepared using Ilford L-4 and Kodak NTE emulsions. Exposure times varied from 3 to 30 weeks. Parallel experiments were performed in which the total counts per minute per milligram of liver slice at each time were determined by standard direct counting techniques. Electron micrographs (magnification approximately 5,000 X) covering a minimum area of 2,000 μ2 of liver were taken of each specimen. The number of background grains in an adjacent area of equal size was determined for each specimen.
Ultrastructural Hepatic Changes Induced by Electrocution
Authors: Schofield B. H. , Grossman I. W.
Published: June 2020

During the course of investigations of ballistic trauma-induced hepatic changes in the goat, cytoplasmic hepatic cell vacuolization was observed in those animals killed by electrocution. To determine the pathogenesis of these vacuoles six castrated Texas Angora goats (Capra hircus) were electrocuted with 60 cycle a-c, 120 ± 5 volts, wall current with a rectal electrode and tongue electrode. Three goats killed with intravenous pentobarbital served as control animals.

We consistently observed hepatic cell cytoplasmic vacuolization by light and electron microscopy in the electrocuted goats (Figure 1 and Figure 2). These vacuoles were bounded by a single smooth-surfaced membrane and a thin rim of amorphous cytoplasmic ground substance. The vacuoles occasionally distended the hepatocytes and measured up to 18μ in greatest diameter.
Synovial Microvasculature in Juvenile Rheumatoid Arthritis
Authors: Clawson C. C. , Lounberg Joyce , Good Robert A.
Published: June 2020

Several authors have placed special emphasis on the role of small vessel vasculitis in the pathogenesis of early synovial lesions of rheumatoid arthritis (RA) (1,2). Electron microscopic studies of the adult form of RA report changes in the synovial fine vessels which include: thickening of the capillary endothelium sometimes to the point of occlusion (3,4), increased numbers of cytoplasmic processes on the lumenal endothelial surface, and widening of the intra-endothelial cell spaces in arterioles and venules (3). We have compared these findings in adult RA with 17 synovial biopsies from 15 patients with the juvenile form of RA including one patient with congenital agammaglobulinemia. Biopsies from eight patients with non-arthritic joint disease were examined as controls. All tissues were fixed in 1% osmium tetroxide in Veronal-acetate buffer (pH 7. 3-7.4). for 2 hours at 0-4° C and embedded in Vestopal W. Sections were cut with glass knives on an LKB or a Sorvall MT 2 microtome and examined in a Philips 200 or RCA 3D microscope.
Some Structural Features of Metaphase Chromosomes of Mice and Men
Authors: Hoskins Godfrey C. , Hoskins Betty B.
Published: June 2020

Metaphase chromosomes from human and mouse cells in vitro are isolated by micrurgy, fixed, and placed on grids for electron microscopy. Interpretations of electron micrographs by current methods indicate the following structural features.

Chromosomal spindle fibrils about 200Å thick form fascicles about 600Å thick, wrapped by dense spiraling fibrils (DSF) less than 100Å thick as they near the kinomere. Such a fascicle joins the future daughter kinomere of each metaphase chromatid with those of adjacent non-homologous chromatids to either side. Thus, four fascicles (SF, 1-4) attach to each metaphase kinomere (K). It is thought that fascicles extend from the kinomere poleward, fray out to let chromosomal fibrils act as traction fibrils against polar fibrils, then regroup to join the adjacent kinomere.
Functional Interpretations of Mitochrondrial Structure in Tissue
Authors: Haydon G. B. , Smith S. O.
Published: June 2020

The functional state of mitochondria at the moment of fixation may be inferred from their morphological conformation. When incubated in a medium which does not support oxidative phosphorylation, isolated mitochondria have the ordinary appearance, but after incubation in a medium which supports oxidative phosphorylation such mitochondria appear condensed.

Near the surface of fresh rat heart muscle, which has been fixed in glutaraldehyde, formaldehyde or osmium tetroxide, occasional groups of mitochondria have a condensed form (Fig 1) while others have the ordinary appearance. Variations from compact to ordinary mitochondria along the tissue surface suggest that at any one time neighboring mitochondria may be in different functional states. However, all mitochondria more than ten to twenty microns from the surface of the tissue block appear ordinary suggesting that these mitochondria were all in an inactive metabolic state when fixation was completed (Fig 2). Perhaps a front of fixative solution permeates the deeper portions of the tissue and stops the oxidative phosphorylation of all mitochondria before actual fixation takes place.