bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of Computers in Electron Microscopy
Authors: Fisher M. , Lee R. J. , McCarthy J. J. 
Published: June 2020

During most of the fifty years since the invention of the electron microscope, the primary hands-on operating role of the microscopist has been scanning specimens, selecting, and recording fields/features of particular interest. Now, microscopy is entering a new era. The advent of microcomputers and microprocessors is about to modify the customary role of microscopists.The new technology will enable them to respond to a growing need for more quantitative data than can be generated by conventional methods based on manual control of data acquisition and processing.During the last 20 years, attention was devoted to the physics of image formation in terms of electron-solid interactions, interference phenomena, and lens performance. During this same period, considerable effort was also put into elucidating the specific nature of many newly discovered structures including crystal defects, interfaces, membranes, second phase particles, and numerous other perturbations of the specimen “matrix.” Sophisticated mathematical descriptions of image contrast, i.e., intensity as a function of position, are now available to predict the appearance of most structures of interest.
Dual Column Wafer Inspection SEM
Authors: Buchanan Robert 
Published: June 2020

With the trend in the semiconductor industry towards smaller and smaller IC structures, there is a growing requirement for visual inspection systems with resolution beyond that of the optical microscope. Further requirements are that wafers up to 6" can be handled, and that any part of the wafer be viewed at normal incidence and tilted at angles up to about 60° with a provision for rotating the specimen about the center of the field of view. The system must neither contaminate the wafer, nor damage it in any way.General purpose scanning electron microscopes have found limited application in wafer inspection for a number of years. These instruments, however, have satisfied only some of the requirements listed above. In particular, the requirement to tilt large wafers to angles as high as 60° has required operation at long working distances with resultant poor image resolution, especially at low accelerating voltage. A further major limitation has been the inability to rotate the wafer about the center of the field of view at all viewing locations.
Morphologic Evidence Suggesting that Bacteria Producing Choriogonadotropin-Like Factor are Revertants of Intracellular Cell-Wall-Deficient Variants
Authors: Acevedo H.F. , Pardo M. , Campbell-Acevedo E.A. , Slifkin M. , Domingue G.J. , Koide S.S. 
Published: June 2020

Bacteria capable of synthesizing and incorporating in their cell membranes a material with immunological, physicochemical, and in vitro and in vivo biological properties similar to those of the human trophoblastic hormone, chorionic gonadotropin (CG), have been isolated from human tissues and urine. The findings are of great biological importance since to date, each one of the strains of bacteria demonstrating the capability to express the CG-like material was isolated from a patient with clinical cancer, and also because it is the first demonstration of biosynthesis of a biologically active “glycoprotein hormone-like” material by procaryotes.In order to establish if morphologic and/or ultrastructural differences exist between a bacterium that synthesizes CG-like material (CG-producer) and those that do not, transmission electron microscopy studies have been done in eight strains of CG-producers. There were five strains of Staphylococcus epidermidis and single strains of Staphylococcus simulans, Streptococcus faecalis, and a bacterium tentatively identified as aerobic “coryneform-like.”
Morphology and Ultrastructure of Mastigocladus Laminosus
Authors: Nierzwicki S. A. , Maratea D. , Balkwill D. L. , Mehta V. B. , Stevens S. E. 
Published: June 2020

Mastigocladus laminosus is a filamentous cyanobacterium (blue-green alga) with a complex morphology. It is the only thermophilic cyanobacterium known to fix atmospheric nitrogen. Relatively little is known of the detailed morphology and ultrastructure of this organism, especially in regard to its nitrogenfixing abilities. The purpose of this study was to characterize the morphology and ultrastructure of M. laminosus, using SEM and TEM respectively.The complex morphology of M. laminosus is shown in Fig. 1. Young filaments had a diameter of ∼2.2 μm and consisted of relatively uniform, rod-shaped cells. The uniformity of these filaments was interrupted only by the occasional appearance of heterocysts (nitrogen-fixing bodies) about 4 μm in diameter (not shown). As young filaments elongated and aged, the older sections increased in diameter to 10-12 μm. Their cells became rounder and less uniform with respect to size and shape. Branches often formed in the older sections, giving rise to new young filaments.
Structure of Freeze-Fractured, Deep-Etched F-Actin
Authors: Ruben G.C. , Allen N.S. , Travis J.L. 
Published: June 2020

High resolution electron microscopic images of F-actin, which had been rapidly frozen, freeze-fractured and deep-etched, have been compared with conventional negatively stained images. Our methods permit the stereoscopic visualization of native actin filament substructureF-actin, prepared by the method of Spudich and Watt (1) was dialized against 2 mM MgCl2and 5 mM Tris at pH 7. F-actin was then negatively stained (1% uranyl acetate at pH 4.5) on 10 nm carbon films (2) or frozen on Balzer's gold pedestals in liquid propane at -190°C. After placing the specimen in a Balzer's 300 freezing microtome, both electron beam guns were out-gassed for two minutes at a current setting of 5. During this process the knife arm (-196°C) covered the sample. The specimen was freeze-etched for 3 minutes at -97°C under the knife arm. Then the sample stage was cooled (-120°C) for two minutes (5xl0-7torr) before the Pt-C was evaporated at a 45° angle to a preset thickness of 2.5 and 2.9 nm on a QSG quartz crystal thin film monitor.
A Scanning Electron Microscopy Study of the Structure of Human Mitotic Chromosomes
Authors: Adolph Kenneth W. 
Published: June 2020

The organization of the fundamental 200-300A chromatin fibers in metaphase chromosomes has been investigated by various techniques of electron microscopy. Thin sectioning studies have suggested that a primary mode of fiber packaging is a radial distribution of loops. In these sectioning studies, the arrangement of fibers was observed by adjusting the concentration of divalent cations (Mg2+, Ca2+) in resuspension buffer to slightly expand the chromosomes and separate the fibers. Scanning electron microscopy has now been applied to obtain information about the surface organization of isolated chromosomes. As with thin sectioning, the degree of expansion of the chromosomes was controlled in a defined and reproducible manner by adjusting the concentration of divalent cations.Chromosomes were prepared from metaphase-arrested suspension cultures of HeLa cells. The isolation buffer contained 50 mM NaCl, 5 mM HEPES pH 7.4, 5 mM MgCl2, 0.5 mM CaCl2, 0.1 mM PMSF, and the mitotic cells were disrupted in a Dounce homogenizer with the aid of detergents.
Freeze Fracture Morphology of Some Synthetic and Naturally Occurring Triacylglycerols
Authors: Rigler Mark W. 
Published: June 2020

The technique of freeze fracture works well for studying intact lipids since conventional dehydration and resin embedding steps for thin sectioning may extract enormous quantities of lipid. It would be advantageous to the investigator who utilizes freeze fracture as a method to be able to identify lipid droplets in preparations of natural or commercially contrived food stuffs, as well as, tissue preparations. The following questions may arise in such studies: a) what type morphological features are present, if any, b) what effect does saturation vs unsaturation have on morphology, and c) is it possible to predict structure on the basis of natural vs synthetic triacylglycerol (TG)?Emulsions of oils were prepared by sonicating mixtures of 10% gum arabic (pH 7.10) and the sample oil (2:1 w/w). Sonicates were cryoprotected with 30% glycerol and fractured at -120°C in a Balzers 360M freeze etch unit.
Element Fluxes in Ischemic Mouse Brain Nuclei
Authors: Mehard C. W. , Akers G. D. , Breeze R. , Ignelzi R. J. 
Published: June 2020

Cerebral edema resulting from cerebral ischemia is an unsolved problem of modern medicine. Perturbations, such as restricting cerebral blood flow, results in severe disturbances in the distribution of Na, K and other inorganic ions and organic molecules between extracellular and intracellular compartments and correlates with ischemic brain swelling (Ignelzi, 1980; Ignelzi and Wickham, 1980). The technique of x-ray microanalysis (STEM-EDS) has permitted us to èvaluate in vivo compartmental element fluxes which occur prior to and during ischemic insult. We report here the preliminary studies on element shifts from mouse brain cortical nuclei under anoxic-ischemic conditions.Cerebral cortex tissue from Swiss-Webster mice was rapidly dissected and frozen at zero time “control” (within 15 seconds) and at four minutes of ischemia. Tissue pieces (1 mm3) were placed on small wooden dowels and rapidly frozen by plunging into an isopentane slush cooled by liquid nitrogen.
The Function of Calmodulin in the Regulation of Smooth Muscle Actomyosin
Authors: Harts home D. J. , Persechini A. 
Published: June 2020

It is known that the contractile activity of all muscle types is regulated by the intracellular concentration of Ca2+ and further it is accepted that the actomyosin systems in these cells contain regulatory proteins which can sense the level of available Ca2+ and cause the muscle to either contract or relax. In skeletal and cardiac muscle this role is fulfilled by the troponintropomyosin complex. However, in smooth muscle the identity of the regulatory components is the subject of controversy. The most popular theory is based on the phosphorylation of the myosin molecule: in the phosphorylated state the Mg2+ -ATPase activity of myosin is activated by actin, whereas in the dephosphorylated state no activation occurs. The alternative theory, proposed by Ebashi and his colleagues, is that regulation is achieved by a thin filament-based regulatory complex, termed leiotonin.Calmodulin is involved only with the phosphorylation scheme and it was shown that the myosin light chain kinase is composed of two subunits, an apoenzyme of molecular weight approximately 100,000 daltons and the regulatory protein, calmodulin. The molar stoichiometry is 1.
Cytochemistry and Electron Microscopy: ACYL Hydrolase and Transferase Reactions
Authors: Barrnett Russell J. , Higgins Joan A. 
Published: June 2020

The use of enzyme cytochemistry with electron microscopy depends on the compromise solution of combining the rigid requirements of both fields. The ability to make the combination has limiting as well as definitive conditions.In illustration of some of the above problems, thiol substituted carboxylic acids should be satisfactory substrates for the demonstration of carboxylic acid esterase activities with Pb++ as the capture reagent. However, utilizing thioacetic acid which is hydrolized by acetylcholinesterase, sites of hydrolysis other than those of carboxylic acid esterases (not affected by the usual inhibitors of esterase activity) are revealed. Among these sites are synaptic vesicles of the myoneural junction, and endoplasmic reticulum and mitochondria of a variety of cells. Contrary to expectations, thiobutyric acid was not split by serum cholinesterase but it, as well as longer chain substrates (thiohexanoic and thio-octonoic acids), was also hydrolysed by enzymes in mitochondria and in the endoplasmic reticulum.
Electron Microscopic Radioautography: The Sites of Nuclear RNA Synthesis in Early Embryonic Cells
Authors: Karasaki Shuichi 
Published: June 2020

The relationship between RNA synthesis and ultrastructural organization of chromatin fibrils was examined in the interphase nuclei of the sea urchin embryos (Arbacia punctulata). The embryos at various stages of development were treated for 1 or 3 hours in sea water with 50 μC/ml of 3H-5-uridine. The samples were fixed in OSO4 or glutaraldehyde (GTA) and embedded in Epon or glycol methacrylate (GMA). Radioautographs were made by applying a thin film of Ilford L4 emulsion directly from an expandable wire loop to thin sections mounted on grids. Following exposure of 10 to 20 weeks, they were developed in Microdol-X or physical developer.In the cleavage and early blastula embryos, each interphase nucleus contains diffusely distributed chromatin and shows only very low incorporation of 3H-uridine into RNA (Fig.1). During these periods, many nucleolus-like bodies occur within the nucleus although they are not labeled with the isotope.
Electron Microscopy of Foot-and-Mouth Disease Virus Crystals and Ferritin-Tagged Antibodies
Authors: Breese S. S. 
Published: June 2020

The interaction of ferritin-tagged antibodies with crystals of foot-and-mouth disease virus (FMDV) has been examined with a homologous and a heterologous antibody. Methods for crystal formation in primary swine kidney cells have been established on a more reproducible basis.The FMDV strain used in these experiments, A1, had been stored at -20°C as the sixth bovine kidney cell passage from the original bovine tongue tissue suspension. It was subsequently inoculated into primary swine kidney cultures for two more passages. The preparation used to inoculate cultures for the experiments reported here was therefore designated BK6PK2. Two-tenths ml of this virus passage was inoculated into each drained prescription bottle. After incubation at 37°C for 90 min, 5-10 ml of maintenance medium was added and the bottles returned to the incubator. Five to six hr after infection, the cell sheets were examined for cytopathic effect.
One-Step Release of DNA Rings From Polyoma Virions
Authors: Vasquez C. , Kleinschmidt A. K. 
Published: June 2020

A tightly packed regularly coiled DNA ring is assumed to be present inside the polyoma virion. Applying the “one-step” technique of nucleic acid extraction from virions while being adsorbed to a protein monolayer, we studied the configurational changes of the DNA.Intact polyoma virions were mixed with DFP-trypsin (100μg/ml) and spread onto a subphase of a mixture of urea and sodium perchlorate (6M and 2M, or 3M and 1M respectively), at pH 8.2 and room temperature. After spreading the film, aliquots were transferred to grids at different periods of time, and the DNA stained by acetonic uranyl acetate.The length distribution of the DNA molecules measured from electron micrographs is shown in Fig. 1. The number of twists present at different times after spreading were also counted. At 12 minutes, with 3M urea and 1M sodium perchlorate in the subphase, the DNA was found to be 85% supertwisted (Fig. 2); 12% was opened to rings, and 3% existed as linear filaments.
Phosphotungstic Acid As An Electron Stain
Authors: Pease Daniel C. 
Published: June 2020

Under certain conditions phosphotungstic acid (PTA) can be used as an effective electron stain for demonstrating polysaccharide moieties in tissue sections. There it selectively combines with the glycoproteins of basement membranes, the mucoid layers associated with brush borders, the mucus of goblet cells, the chondroitin sulfate of cartilage matrix, glyco-gen, and “glycocalyces” in general. The initial published investigation indicated that an acid environment was essential for this specificity, but the effect of pH was not systematically explored.Rib cartilage of newborn rats was chosen for a detailed study of the effects of pH on PTA staining, particularly to provide ancillary information on the formation, secretion and deposition of chondroitin sulfate. Cartilage was prepared without chemical fixation by “freeze-substitution” with 70% glycol, or by “inert dehydration” with glycol at room temperature. Dehydrated material was embedded in prepolymerized hydroxy-propyl methacrylate without an intermediate solvent.
Selective Staining of Acid Mucopolysaccharides By Ruthenium Red
Authors: Luft J. H. 
Published: June 2020

Ruthenium red is one of the few completely inorganic dyes used to stain tissues for light microscopy. This novelty is enhanced by ignorance regarding its staining mechanism. However, its continued usefulness in botany for demonstrating pectic substances attests to selectivity of some sort. Whether understood or not, histochemists continue to be grateful for small favors.Ruthenium red can also be used with the electron microscope. If single cells are exposed to ruthenium red solution, sufficient mass can be bound to produce observable density in the electron microscope. Generally, this effect is not useful with solid tissues because the contrast is wasted on the damaged cells at the block surface, with little dye diffusing more than 25-50 μ into the interior. Although these traces of ruthenium red which penetrate between and around cells are visible in the light microscope, they produce negligible contrast in the electron microscope. However, its presence can be amplified by a reaction with osmium tetroxide, probably catalytically, to be easily visible by EM. Now the density is clearly seen to be extracellular and closely associated with collagen fibers (Fig. 1).
Comparison of Cholesterol Extraction from Tissues During Processing for Electron Microscopic Radioautography
Authors: Hedley-Whyte E. Tessa , Uzman Betty G. 
Published: June 2020

Radioautographic studies of lipid metabolism with the electron microscope have been limited by the large losses of lipid which occur during the usual dehydration and infiltration procedures. In this study different methods of processing tissue for electron microscopic radioautography have been compared with respect to the extraction of cholesterol-1, 2-3H from labeled mouse liver and nerve.In all methods primary fixation had been in 10% formalin for several months followed by washing overnight. Post-fixation for one hour in Dalton's chrome osmium and staining in 1% uranyl acetate in 10% formalin resulted in small but constant losses. Four methods were assessed: 1) graded acetone dehydration with propylene oxide and epon-araldite mixture infiltration, 2) exposure to 0.5% digitonin in 50% ethanol for 1 hour before post-fixing in osmium followed by procedure 1, 3) Durcupan embedding, and 4) limited dehydration followed by embedding in an epon:araldite mixture (modified Idelman).
Freeze-Etching Simplified
Authors: Steere Russell L. 
Published: June 2020

Freeze-etching, as a tool in the preparation of biological specimens for electron microscopy, has seen relatively little use since it was introduced in 1957. The involved procedure, originally described, and, until recently, the cost of special equipment, must certainly have played a part in the failure of freeze-etching to become a commonly used technique. Efforts to solve some of the problems have resulted in the development of a modified freeze-etching module that can fit on nearly any vacuum evaporator and will permit the production of good specimens by an unskilled technician in less than one-half hour.The freeze-etching module (Fig. 1) consists of a collar (A) with two opposing hollow tubes supported by small collars so that the specimen end of the specimen tube (D) can rotate within the rotatable cold shroud (F).
Stellate Cells in the Pituitary Gland of the Salamander
Authors: Cardell Robert R. 
Published: June 2020

The fine structure of five cell types in the pars distalis of the salamander [Notophthalmus (Triturus) viridescens viridescens] pituitary gland has been described. Four of these possess characteristic secretory granules (figure 1) and apparently they are involved in the synthesis and secretion of pituitary hormones. The other cell (Cell type #5 or “stellate cell”) does not possess characteristic secretory granules (figures 1 and 2) and they show a morphology which does not suggest a secretory function. The present report extends the observations on the fine structure of the stellate cell and considers, in addition, the distribution of this cell throughout the pars distalis.The stellate cell displays many slender, cytoplasmic extensions which penetrate between the secretory cells (figure 1). These extensions contact processes from other stellate cells and desmosomes are found at the points of contact. Moreover, desmosomes are frequently located between the stellate cells and the secretory cells (figure 2). Thus, the stellate cells are not only linked to each other throughout the pars distalis, but to each secretory cell as well. Stellate cell processes contact the outer basement lamina of the pericapillary space and often such processes follow the contour of the basement lamina for considerable distances. They do not penetrate, however, into the pericapillary space.
The Morphology of the Pecten Oculi and the Conus Papillaris
Authors: Dunn R. F. 
Published: June 2020

In this study, the pecten of the house finch, and the conus of the gecko, Eublipharis, were utilized. The structure of the house finch pecten resembled that of the pigeon. The capillary endothelium is characterized by an extensive luminal and abluminal system of plasma membrane plications (Fig. 1, LP and AP). The luminal ridges vary in length from 1.3 - 2.9μ, and are 40-90 mμ in width. The luminal and abluminal plications are separated by the narrow, rather dense endothelial cytoplasm which contains free ribosomes and dense mitochondria in addition to granular cytomembranes. The abluminal ridges are generally shorter, and rest on a basement membrane. Many of the pecten surface capillaries are separated from the vitreous by only a short distance of about 1μ. In other regions the capillaries are surrounded by pigmented cells, which contain smooth surfaced, very osmiophilic granules up to 1.6μ in diameter, a few smaller, irregularly shaped granules and the usual compliment of cytoplasmic organelles (Fig. 2).In sharp contrast to the pecten, the endothelium of the conus is relatively smooth and lacks any surface foldings as well as any fenestrations (Fig. 3). The endothelial basement membrane is separated from that of the pigment cell by a variable extracellular connective tissue space containing many collagen fibrils. The pigment cells contain melanin granules similar to those of the pecten (Fig.4).
Turbomolecular Pumped Electron Microscopy of Rubella Virus (In BHK Celis)
Authors: Taylor A. B. , Cole G. C. , Holcomb M. A. , Baechler C. A. 
Published: June 2020

An aliquot from a continuous fermenter culture of baby hamster kidney cells (BHK-21 Clone PD-4) (Wistar) maintained in Ca free Eagle's Basal Medium containing 2% Kaolin adsorbed fetal calf serum was planted in spinner flasks at 300,000 cells per ml, total volume 600 ml. After equilibration for one day at 35°C to insure that cells were in log phase, the culture was infected with the M-33-AGMK25 BHK-219 strain of rubella at an input multiplicity of about 6 TCID50 per cell. The virus was identified with specific rubella antiserum.Preliminary experiments had shown that such cultures would reach a peak or plateau HA titer of approximately 1:64, 24 hrs after inoculation and would continue to yield virus for 6 to 12 days. One hundred ml aliquot harvests were withdrawn daily and the culture was returned to volume with growth medium and incubation continued. The harvested cells were spun down rapidly at 2500 rpm per 15 mins., fixed in 3.7% gluteraldehyde in Ca free phosphate buffer saline, and post fixed in osmium tetraoxide. After dehydration, the cells were embedded in Epon 812 and cured approximately 20 hrs at 60°C.