bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Use of Styrenes as Embedding Media for Electron Microscopy
Authors: De-Lamater Edward D. , Johnson Eric , Schoen Thad , Whitaker Cecil 
Published: June 2020

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.
Scanning and Transmission Electron Microscopic Evaluation of Parathyroid Glands
Authors: Capen C. C. , Fetter A. W. 
Published: June 2020

Parathyroid glands of normal animals were composed of groups of chief cells surrounded by a continuous basement membrane and fine collagen fibers (Fig. 1). Scanning electron microscopy demonstrated chief cells to be arranged into spheroidal or ovoid groups interconnected by collagen fibers (Fig. 2). Tubular profiles of capillaries were intimately applied to the surface of the spheres.Present evidence indicates that the parathyroids contain a single type of secretory cell concerned with the elaboration of one hormone. Chief cells interpreted to be in an inactive stage of the secretory cycle predominated in most species. Organelles other than mitochondria were poorly developed and numerous lipid bodies were present. Active chief cells occurred less frequently and had well developed organelles concerned with protein synthesis and packaging of secretory products.Secretory granules were readily demonstrated within chief cells. They were more numerous in active than inactive chief cells. The granules were small, ranging from 100-300 μ in greatest diameter, surrounded by a closely applied limiting membrane, and composed of fine dense particles. The granules moved peripherally and the limiting membrane fused with the plasma membrane of the cell.
Fine Structure of the Ultimobranchial Gland in the Chick
Authors: Chan A. S. 
Published: June 2020

Although the ultimobranchial gland of the chick has been shown to contain large amounts of calcitonin relatively few reports have been published on its fine structure. In the present study, the ultrastructure of the chick ultimobranchial gland, with emphasis on the cells which appear to be the producers of the hormone, will be examined. Ultimobranchial glands were obtained from twenty 2-week-old chicks and fixed in glutaraldehyde followed by osmium tetroxide.The gland is composed of aggregate of cords and clusters of cells interspersed with variable numbers of cyst-like cavities. Two parenchymal cell types, namely, light and dark cells can be recognized (Figs. 1,2,3). Epithelial cells, varying from columnar to cuboidal, line the cavities of the cysts.Light cells form the majority of the cell types (Fig. 1). The cytoplasm is characterized by the presence of membrane-limited secretory granules, measuring from 100 to 350 mμ in diameter. The contents of the secretory granules vary in electron density from moderate to extreme (Figs. 1,2). Secretory granules are distributed randomly in the cytoplasm although some are lined near the cell membrane.
Cytoplasmic Structures in Insect Granular Hemocytes
Authors: Hagopian M. 
Published: June 2020

Femoral segments from the metathoracic leg of the freshly molted cockroach nymph, Leucophaea maderae, were removed and were prepared for electron microscopy. The femoral cuticle with underlying epidermal cells encloses muscle, nerves, tracheae, tracheoles, and the hemocoel. In the insect open circulatory system the hemocoel contains hemolymph and hemocytes. Some of the known functions of insect hemocytes are phagocytosis, encapsulation, melanization, Wound healing, coagulation and possible transformation into other tissues. Previous studies of the agranular and granular hemocytes however lack the fine structure that is helpful in determining cellular function.The several different types of granular hemocytes have a general elliptical appearance, large nucleus, and prominent cytoplasmic granules. The most abundant type of granules are the membrane-bounded, roughly spherical, opaque inclusions which average about 1 to 2μ in diameter. These dense inclusions resemble vertebrate melanosomes. Other granules with an organized substructure are reminiscent of the vertebrate premelanosomes (Figs. 1, 2). In certain planes of section the premelanosome-like granules reveal that the internal configurations are microtubules which measure about 250A in diameter.
Isolated Plasma Membranes of Sea Urchin Eggs
Authors: Inoue S. , Preddie E. C. , Guerrier P. 
Published: June 2020

From electron microscope studies of thin sections the sea urchin egg is known to be surrounded by the peripheral membrane system which is made up of the outer coat (vitelline membrane), which elevates from an egg surface after fertilization and becomes a part of the fertilization membrane, and the plasma membrane. In these experiments an effort has been made to isolate plasma membranes of sea urchin eggs and these isolated membranes were observed in the electron microscope.The vitelline membrane of the eggs from the sea urchin Strongylocentrotus purpuratus was at first digested away by the treatment with 0.02% trypsin in 0.01 M Tris-HCl buffer (pH 8.0) for 5 minutes at 28°C. The plasma membranes were then isolated according to the method of Song et al. which was used for the isolation of rat liver plasma membranes. The vitelline membrane-free eggs were gently homogenized in 10-3 M NaHC03 (pH 7.5) and freed membranes were collected by centrifugation over a discontinuous sucrose gradient preparation.
Modification of Pyrrolizidine Toxicity by Altering Hepatic Microsomes
Authors: Allen J. R. , Carstens L. A. 
Published: June 2020

The pyrrolizidine alkaloid, monocrotaline is capable of producing necrosis, megalocytosis, carcinogenesis and veno-occlusive disease of the liver. Kidney lesions include glomerular hyalinization, necrosis of afferent arterioles and disruption of the arterial walls. Capillary occlusion by fibrin and platelet thrombi and hypertrophy of the smooth muscle cells in the small muscular arteries of the lung precede the development of pulmonary hypertension. The means by which this alkaloid produces the above mentioned lesions has not been clarified. Butler et. al. have reported that pyrrole metabolites are capable of causing pulmonary and hepatic lesions similar to monocrotaline. In the presently reported study it is shown that the enhancement (phenobarbital) or inhibition (chloramphenicol) of microsomal enzymes is instrumental in determining the magnitude of the lesions and the survival rate of animals.Male, Sprague Dawley rats were divided into 6 groups and received monocrotaline, phenobarbital, phenobarbital-monocrotaline, chloramphenicol, chloramphenicol-monocrotaline, and physiological saline (Table 1). Rate of gain was reduced and 50% of the animals in the phenobarbital-monocrotaline group expired within 14 days following the injection of monocrotaline.
Experimental Amyloidosis Induced by Immune Complex
Authors: Kawaoi A. 
Published: June 2020

Numbers of immunological approach have been made to the amyloidosis through the variety of predisposing human diseases and the experimentally induced animals by the greater number of agents. The results suggest an important role of impaired immunity involving both humoral and cell-mediated aspects.Recently the author has succeeded in producing amyloidosis in the rabbits and mice by the injections of immune complex of heat denatured DNA.The aim of this report is to demonstrate the details of the ultrastructure of the amyloidosis induced by heterologous insoluble immune complex. Eleven of twelve mice, dd strain, subcutaneously injected twice a week with Freund's complete adjuvant and four of seven animals intraperitonially injected developed systemic amyloidosis two months later from the initial injections. The spleens were electron microscopically observed.
Microcraters in Lunar Samples
Authors: McKay David S. 
Published: June 2020

Introduction. Samples of rock, mineral, and glass fragments returned by Apollo 11 and 12 contain a variety of microcraters which were formed by the impacts of small projectiles. The craters are especially prominent in some of the small glass spherules and related forms.Crater types. It is possible to classify these microcraters on the basis of morphology as seen by the scanning electron microscope. Type I microcraters (Figure 1) show the following characteristics:A. A glassy central area is present which has been melted by the impact. This glass is primarily material from the target but may also contain melted projectile material. The central area is normally very smooth and may or may not have a smooth raised lip.
Computer Enhancement of Electron Micrographs
Authors: Nathan Robert 
Published: June 2020

The digital computer with associated video camera scanner equipment can be used in conjunction with the microscope's best performance to give improved and ultimately perhaps atomic resolution. Examples of computer application emphasize space photography where the computer enhancement methods originated. The following operations evolved as a result of working with television images: geometric correction, photometric correction, random noise removal, periodic noise removal, scan-line noise removal, and modulation transfer function ,(MTF) correction (compensation for attenuation of spatial high-frequency components).Other examples include the enhancement of a micrograph of negatively stained catalase, a micrograph of some microtubules and a video recording of indathrene olive. In a crystal, because of its periodicity, improvement can be obtained in the signal to noise ratio by translating and superimposing the image upon itself.
Computer Synthesis and Filtration of Electron Micrographs of Simple Molecular Objects
Authors: Welton T. A. 
Published: June 2020

A flexible computer program for the IBM 360/91 gives us the capability of synthesizing fairly realistic electron micrographs in the form of computerproduced transparencies which have all of the essential features of actual electron-exposed emulsions. We can control the assumed properties of the illuminating electron beam, the contents of the object plane, the electron optical properties of the objective and magnification system, and the properties of the detector system (emulsion). Statistical error (noise) can be realistically introduced. The resulting transparencies give very striking visual evidence concerning the quality of the information obtainable about simple molecular (DNA) samples under various interesting assumptions.As presently operating, we can conveniently place up to three complete periods of the double helical DNA structure (100.8 Å) in the object plane. The object is assumed to repeat indefinitely with a rectangular unit cell, so that a discrete Fourier series can be used. The Fourier coefficients of the image wave (just after sample passage) are computed from the known atomic coordinates.
Stereoscopic Analysis of Dislocation Distributions from Electron Micrographs
Authors: Thomas L. E. , Cuddy L. J. 
Published: June 2020

The use of stereo pairs of electron micrographs for quantitative analysis of defect structures offers several advantages over methods which use single micrographs: stereoscopic viewing aids in comprehending complicated 3-dimensional structure. Defect densities can be measured locally, i.e. as a function of depth in the specimen rather than as an average over the foil thickness. The depth definition afforded by 3-dimensional viewing largely eliminates problems of image overlap. The depth dimension can be measured from the micrographs. In this paper, stereo techniques for analyzing dislocation distributions will be discussed along with results obtained using high voltage electron micrographs of very thick foils.Although the practice of electron stereomicroscopy with diffraction contrast images is not yet widespread, the technique is not difficult. Two different views of the same specimen detail are obtained by tilting the specimen between exposures. With diffraction contrast, the operating reflection and Bragg deviation must be kept the same so that any differences in the position and appearance of the defect images is due to the change in viewpoint.
Phase Contrast in Electron Microscopy
Authors: Johnson H. M. , Parsons D. F. 
Published: June 2020

Phase shifting of scattered or non-scattered waves into antiphase with respect to each other has provided the most advantageous optical contrasting technique for light microscopy. Analogously, attempts have been made in electron microscopy to achieve phase contrast, both in-focus and out-of-focus. Results have been complicated by lens aberrations, power supply instabilities, interpretation of defocused images and, in the case of lattice images, by the question of the actual imaging mode.Defocus contrast has been further complicated by lateral displacement of dark field images from the corresponding bright field image as commonly observed with inorganic crystals (e.g. MgO). By means of image plane detectors (Fig. 1) the defocus contrast variation of polystyrene latex spheres (P.S.L.) (Fig. 2) has been related to the lateral shift of dark field images arising from carbon-carbon nearest neighbor scattering. Lateral displacement arises from defocusing and from spherical aberration at focus (resulting in the variation of in-focus contrast for different microscopes used without an objective aperture).
Effects of Reserpine on Abdominal Paraganglia at the Fine Structural Level
Authors: Mascorro J.A. , Yates R. D. 
Published: June 2020

Past investigations with the electron microscope have established the presence of two cell types in the abdominal paraganglia. Type I (glomus or chief) cells exhibit numerous cytoplasmic granules similar to the catecholamine containing ones of the adrenal medulla whereas Type II (sustentacular or supporting) cells lack such granules and send thin cytoplasmic processes partially or completely around clusters of Type I cells. Mascorro and Yates speculated that the granules of Type I cells might contain catecholamines. The present research was undertaken to determine if the amine depleting drug reserpine affected the fine structure of the cytoplasmic granules.Eight white mice 10-18 days old were used for these experiments. Three of the animals received two subcutaneous injections of reserpine (2.5 mg/ kg) and. were sacrificed 48 hours after the onset of treatment. All animals were prepared for light and electron microscopy by perfusion with 2% glutaraldehyde in 0.1 M phosphate buffer followed by additional fixation in 1% osmic acid.
Ultra-structural Changes Induced in the Heart by In-vitro Perfusion
Authors: Schowengerdt C. G. , Basom C. R. , Wolf G. L. 
Published: June 2020

Veterans Administration Hospital, Cincinnati, Ohio 45219 Departments of Surgery, Anatomy, and Laboratory Animal Medicine, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45219Dilute blood or plasma was used to perfuse mongrel dog hearts for 20-27 hours. The hearts were maintained with a Bramson membrane oxygenator at a pO2 of 200-250 mm.Hg and a pCO2 of 28.2-42.0 mm.Hg on a Belzer-Truman pump at 20-52 pulsations per minute. Warm ischemia time with excision of the heart averaged 6.6 minutes. The perfusate pressure was an average of 70/30 mm.Hg (systolic/diastolic) at a temperature of 12 to 20 degrees C. Of the various factors tested for functional preservation, a warm ischemia time of less than 20 minutes, a perfusate temperature of 12 to 15 degrees C., and a pressure of more than 40/15 mm.Hg were found to be most essential for preservation of functional viability. Functional viability was determined by the capacity of the heart to sustain rhythmic co-ordinated contractions following defibrillation.
Biochemistry and Morphology of Fragmented Sarcoplasmic Reticulum
Authors: Peter J. B. , Fiehn W. , Dunn Robert F. 
Published: June 2020

The function of the sarcoplasmic reticulum (SR) is well defined, but much confusion exists about the role of the SR in the contraction-relaxation cycle of slow-twitch muscles. Fragmented SR (FSR) was isolated from different guinea pig muscles. The muscles were classified as fast-twitch-red, fast-twitch-white or slow-twitch-intermediate according to their contractionrelaxation times and the histochemical characteristics of the component fibers.The kinetics of calcium accumulation showed no difference between FSR from fast-twitch-red or fast-twitch-white muscles, and the yield of FSR (expressed as mg vesicle protein per gram of muscle) was the same. By contrast the amount of FSR obtained per gram of slow-twitch-intermediate muscle was only half as high. Likewise, the maximal amount of calcium that could be stored in the presence of oxalate by FSR from slow-twitch-intermediate muscles was only half that of FSR from fast-twitch muscles.
Morphological Maturation in Myeloproliferative Virus
Authors: James Arnold Wm. , Soule Herbert D. , Northup N. E. 
Published: June 2020

Myeloproliferative virus (MPV) grows abundantly with high virulence in a stable cell line, MCF-6 and well in short-term BALB/c mouse embryo tissue culture infected from MCF-6. MPV was partially purified from culture supernatant by ultracentrifugation, fixed in buffered 3% glutaraldehyde followed with buffered 1% OSO4, embedded in Epon, sectioned and stained with lead and uranium. Cells from MCF-6, embryo cultures, and leukemic mice infected with cell-free MCF-6 supernatant were prepared similarly, or according to Hirsch and Fedorko.All preparations contain MPV profiles resembling the C particles found associated with murine leukemias, avian leukoses, and Rous sarcoma. MPV buds from the outer surface (Fig.2) or, rarely, into cytoplasmic vesicles of the host cell and retains the empty-centered, concentric form commonly considered to be that of immature C particles until at least a short time before separation.
Three Dimensional Fourier Analysis of the Ribonucleoprotein Particle (Ribosome) Helix of Entamoeba Invadens
Authors: Lake James A. , Slayter Henry S. 
Published: June 2020

Cysts of Entamoeba Invadens contain large ordered arrays of closely packed helices which absorb strongly in the ultraviolet. The helices consist of small, approximately spherical particles about 250Å in diameter. Several lines of evidence have indicated that they may be ribosomes. We shall refer to these particles as ribosomes in this paper.DeRosier and Klug (1) have demonstrated that it is possible to reconstruct a three dimensional object from two dimensional projected images, i.e. micrographs, provided that sufficient views, of individual molecules are available. A single view (micrograph) of one ribosomal helix provides many views of individual ribosomes.
Nuclear Inclusions Found in Endometrium Medroxyprogesterone Acetate Therapy
Authors: Roberts D. K. , Powell L.C. , Busby Nola 
Published: June 2020

Medroxyprogesterone Acetate is currently under clinical evaluation for use as a contraceptive agent. At the University of Texas Medical Branch in Galveston, Texas, 1,065 females in the reproductive age group have been given this agent. Intramuscular injections of 150 mgm in depot form have been given at three month intervals. The experience involves over 14,000 woman months of successful contraception.Concurrent with this large study, endometrial biopsies have been taken on sixty selected patients and categorized at 5-day intervals so that a minimum of three biopsies at each time period were included. These biopsies were submitted to light and electron microscopic evaluation. Preliminary evaluation of this biopsy series has revealed unusual nuclear inclusions at the ten and fifteen day post-injection interval (Figure 1.).
Comparative Morphology of Intercellular Bridges Between Developing Germ Cells of the Ovary
Authors: Ruby J. R. , Dyer R. F. , Skalko R. G. , Gasser R. F. , Volpe E. P. 
Published: June 2020

An electron microscope examination of fetal ovaries has revealed that developing germ cells are connected by intercellular bridges. In this investigation several species have been studied including human, mouse, chicken, and tadpole (Rana pipiens). These studies demonstrate that intercellular connections are similar in morphology regardless of the species.Basically, all bridges are characterized by a band of electron-dense material on the cytoplasmic side of the tri-laminar membrane surrounding the connection (Fig.l). This membrane is continuous with the plasma membrane of the conjoined cells. The dense material, however, never extends beyond the limits of the bridge. Variations in the configuration of intercellular connections were noted in all ovaries studied. However, the bridges in each individual species usually exhibits one structural characteristic seldom found in the others. For example, bridges in the human ovary very often have large blebs projecting from the lateral borders whereas the sides of the connections in the mouse gonad merely demonstrate a slight convexity.
Two Developments - A Superconducting Microscope Conversion and A Precision High Voltage Divider
Authors: Worsham R. E. , Mann J. E. , Richardson E. G. , Ziegler N. F. 
Published: June 2020

Two elements in the chain of development for a 500 kV high resolution microscope have been completed for initial experimental evaluation. They are a conversion of a Siemens Elmiskop I to use a superconducting objective lens and a 150 kV precisely regulated accelerating supply.The superconducting microscope, shown in Fig. 2 is designed as an optical bench for proving the cryostat, lenses, stage mechanism, and other parts prior to the design of a superconducting column for 500 keV. The lens as shown in Figs. 1 and 2 mounts on the removable bottom plate of the 7-liter helium vessel. The vessel is supported and can be clamped rigidly by the four sets of G-10 epoxy-glass posts. Radiation Shields I and II are concentric with the helium vessel. They are cooled by the boil-off helium vapor to about 30 and 130°K, respectively. All electrical leads are carried into the helium vessel through the four symmetrically located vents. Cooldowns from 77°K requires about 30 liters of liquid helium and the boil-off rate is 0.3-0.5 1/HR at either 4.2 or ∼ 1.8°K.