bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Transitions in Escherichia coli Ribosomal RNAs as Visualized by Dedicated STEM
Authors: Wall J.S. , Maridiyan V. , Tumminia S. , Hairifeld J. , Boublik M. 
Published: June 2020

The high contrast in the dark-field mode of dedicated STEM, specimen deposition by the wet film technique and low radiation dose (1 e/Å2) at -160°C make it possible to obtain high resolution images of unstained freeze-dried macromolecules with minimal structural distortion. Since the image intensity is directly related to the local projected mass of the specimen it became feasible to determine the molecular mass and mass distribution within individual macromolecules and from these data to calculate the linear density (M/L) and the radii of gyration.2 This parameter (RQ), reflecting the three-dimensional structure of the macromolecular particles in solution, has been applied to monitor the conformational transitions in E. coli 16S and 23S ribosomal RNAs in solutions of various ionic strength.In spite of the differences in mass (550 kD and 1050 kD, respectively), both 16S and 23S RNA appear equally sensitive to changes in buffer conditions. In deionized water or conditions of extremely low ionic strength both appear as filamentous structures (Fig. la and 2a, respectively) possessing a major backbone with protruding branches which are more frequent and more complex in 23S RNA (Fig. 2a).
New Developments in Thaw-Fixation
Authors: Haggis G.H. 
Published: June 2020

Some years ago we introduced a thaw-fix technique for SEM viewing of internal cell structure1. In thisptechnique cells or tissues are frozen unfixed, fractured at -170 to -190°C and thawed into fixative at room temperature. In early work we infiltrated cells with glycerol or dimethylsulphoxide (to 25-30%) prior to freezing, to avoid ice crystal artifact during freezing and thawing. This infiltration took 20 mins, to 1 hr. with the possibility of ultrastuctural change during this time, since the cells were unfixed. Results for interphase chromatin were interesting but cytoplasmic structure was not well preserved. We have now improved our techniques for rapid freezing and rapid thawing and report results here for fresh material, rapidly frozen without cryoprotectant, showing excellent cytoplasmic preservation. Interphase chromatin shows structural detail comparable to that obtained earlier with glycerol cryoprotection.3T3 cells were grown on 20μm fibrin films, rapidly frozen by propane-jet freezing, fractured in a Balzers BAF 400 freeze-etch unit at -170°C and thawed into a fixative of Bershadsky buffer3 + 1.5% glutaraldehyde.
Ultrastructural Evaluation of Ischemic Skeletal Muscle Reperfused with Oxygen Free Radical Scavengers
Authors: Mathur A. , Russell R.C. , Roth A.C. , Wagahoff D. 
Published: June 2020

Skeletal muscle is very sensitive to ischemia. A prolonged preoperative ischemic interval decreases the chances for successful replantation of an amputated limb. Recent experimental work has implicated toxic oxygen free radicals produced during reperfusion of ischemic tissue to be responsible for some of the observed deleterious cellular changes. Selected oxygen free radical scavengers have been used to increase skeletal muscle survival following total ischemia. This study examined the effect of systemic administration of a superoxide free radical scavenger, superoxide dismutase (SOD), and a hydroxyl radical scavenger, dimethylsulfoxide (DMSO) just prior to reperfusion, on the ultrastructure and function of ischemic rabbit anterior tibialis muscle.White male New Zealand rabbits were used for this study. The right hind limb of each rabbit was made ischemic by dissecting and clamping the femoral artery and vein proximal to the bifurcation of the profundus artery and vein. A penrose tourniquet was also placed around the knee. The animals were divided into groups subjected to either 5 or 8 hours of ischemia.
Confocal Laser Microscopy of Physiologically Characterized Fluorescently Labeled Central Nervous System Neurons
Authors: Turner J.N. , Swann J. , Smith K. , Siemens M. , Szarowski D. , Collins D.N. 
Published: June 2020

Confocal laser scanning microscopy (CLSM) is capable of three-dimensional imaging of fluorescently labeled single cells. Efficient detection via a photomultiplier and optical sectioning with high rejection of light from other specimen levels make it possible to image cells surrounded by either labeled or unlabeled tissue. It is no longer necessary to restrict high resolution light microscopy to cultured cells or those near the surface of a tissue sample. Cells can be observed üin situ” in a physiologically characterized environment. Central nervous system neurons can be electrophysiologically characterized and then injected with a fluorescent dye such as lucifer yellow. The CLSM can excite the dye and image the fluorescent emission in thick tissue preparations (hundreds of micrometers) making possible a new approach to the correlation of physiology and anatomy.Brain slices 350 μm thick were obtained from hippocampus and inferior colliculus of immature rats and incubated in oxygenated artificial cerebrospinal fluid. Cells were penetrated with micropipets, characterized electrophysiologically and ionophoretically injected with 5% lucifer yellow in LiAc.
An SEM/TEM study of structures associated with bacteroids in peanut (Arachis hyppogaea L.) root nodules
Authors: Emerson C. J. , Bal A. K. 
Published: June 2020

Nitrogen-fixing peanut root nodules have highly specialized, large spherical bacteroids and show higher acetylene-reduction activity than the nodules of other legumes induced by the same strain of rhizobia. Differences are also found in their anatomical organization and with regard to bacteroid-associated organelles and other structures (dense bodies) found on the host-symbiont interface. In this investigation, further description of these organelles and structures was made at different stages of development in a correlated SEM/TEM study.Arachis hypogaea L. cv. Jumbo Virginia plants were grown in environmental growth chambers and inoculated with Rhizobium sp. 32Hl. For TEM, slices of nodules were fixed in Karnovsky's fixative in Sorensen's phosphate buffer, pH 7.2 for 1 h at 4°C. Tissues were rinsed in buffer, post-fixed with 1% phosphate-buffered osmium tetroxide for 1 h at 4°C and dehydrated in ethanol. 1% p-phenylenediamine was added at the 70% ethanol step (30 min) to preserve lipids.
Structure of the surface of thornless blackberry fruits: Relevance to post harvest weight loss
Authors: Jones S. N. , Sapers G. M. , Douglas F. W. , Dobson Eastern T. O. 
Published: June 2020

Strategies to improve marketability of small fruits include the identification of characteristics that contribute to longer shelf life. One characteristic of a durable berry is that it retains moisture after harvest and resists desiccation. In our study of 10 thornless blackberry cultivars and selections during refrigerated storage, weight loss varied from 1% to 3% per day and rates were linear for 10 days. Fluid leakage was not a factor, and the primary source of weight loss was concluded to be transpiration. Microscopy was performed to identify structural correlates of berry weight loss. Surface wax on plant structures is known to be a barrier to water loss.Representative berries from the hand-selected fruits, sorted for weight loss analysis, were processed for microscopy 24-36 hr after harvest, during which time the fruits were held at 0-1 C. Samples were fixed with glutaraldehyde and osmium tetroxide, dehydrated with an acetone series, and embedded in Spurr's resin.
Maize Necrotic Lesion Virus Particles and Associated Cellular Inclusions
Authors: Bradfute O. E. , Louie Raymond 
Published: June 2020

Maize necrotic lesion virus (MNLV), a newly found soil-borne virus, is apparently one of a complex of viruses infecting roots of maize (Zea mays L.) in northern Ohio (1). Maize roots become infected when plants are grown in infested, field soil that has undergone air-dry storage or in autoclaved, greenhouse soil infested with diseased roots. Symptoms on leaves of rub-inoculated maize and other monocot seedlings first appear as chlorotic local lesions that become necrotic after 24-36 hr.Numerous isometric virus particles of two sizes, ca. 17 and 29 nm in diameter, were observed in crude extracts from MNLV lesions negatively stained in phosphotungstic acid, pH 4.8 (Fig. 1). At pH 6.9 the larger virus particles were frequently stain-penetrated and clumped together or embedded in an amorphous matrix (Fig. 2). MNLV-infected cells were also examined in thin sections cut from fixed and embedded chlorotic lesions (Fig. 3-4). In the cytoplasm of some mesophyll cells, numerous isometric virus particles of both sizes were clearly recognized in close proximity to each other and to masses of electron-dense, amorphous inclusions.
Alveolitis due to inhalation of acrylic polymers: Report of a case
Authors: Minda J. M. , Johns L. W. , Barrett T. E. , Mayock R. L. , Pietra G. G. 
Published: June 2020

Acrylic polymers are increasingly used in dental laboratories for preparation of prostheses. In the past, dental technicians have developed pneumoconiosis due to inhalation of silica dust or heavy metal alloys, but to our knowledge, no other cases of lung disease due to inhalation of acrylic dust have been previously reported.The patient, a dental student, was admitted to the Hospital of the University of Pennsylvania for evaluation of persistent bilateral interstitial infiltrates and cough. An open lung biopsy was performed to determine the cause of the infiltrate. The biopsy specimen revealed interstitial lymphocytic infiltrates and intra-alveolar accumulation of “foamy” macrophages (Fig. 1) suggesting lipoid pneumonia. Since he did not use medications containing mineral oil or had obstructive lesions of the airways, electron microscopy examination of the biopsy specimen was performed. Transmission electron microscopy (TEM) revealed accumulation of macrophages in the alveolar space and interstitium, containing numerous electron-lucent vacuoles of varying size (Fig. 2).
Ultrastructural comparison of prolactin adenomas of pituitary in men and women
Authors: Caughey R.C. , Kalyan-Raman U.P. 
Published: June 2020

Prolactin producing pituitary adenomas are ultrastructurally characterized by secretory granules varying in size (150-300nm), abundance of endoplasmic reticulum, and misplaced exocytosis. They are also subclassified as sparsely or densely granulated according to the amount of granules present. The hormone levels in men and women vary, being higher in men; so also the symptoms vary between both sexes. In order to understand this variation, we studied 21 prolactin producing pituitary adenomas by transmission electron microscope. This was out of a total of 80 pituitary adenomas. There were 6 men and 15 women in this group of 21 prolactinomas.All of the pituitary adenomas were fixed in 2.5% glutaraldehyde, rinsed in Millonig's phosphate buffer, and post fixed with 1% osmium tetroxide. They were then en bloc stained with 0.5% uranyl acetate, rinsed with Walpole's non-phosphate buffer, dehydrated with graded series of ethanols and embedded with Epon 812 epoxy resin.
Intracellular localization of hantan (HFRS) virus antigens by means of immune colloidal gold electron microscopy
Authors: Tao Hung , Semao Xia , Tungxing Chao , Zinyi Chou , Boquan Chen 
Published: June 2020

Hantan (HFRS) virus, the etiologic agent of Hemorrhagic Fever with Renal Syndrome has been provisionally classified as a new genus of Bunyaviridae. We have described, in our previous papers, some distinctive morphogenetic features in HFRS virus infected cells namely, intracytoplasmic inclusion bodies (lb), virus associated granules, viral antigen layer(Val) etc, The actual roles of these structures, however, remain unknown and warrant further study. This paper reports the results of our study using immune colloidal gold electron microscopy.Chinese HFRS isolates, A9 & R22, derived from Apodemus agrarius and Rattus nervegicus respectively were grown in Vero E-6 cells, harvested for EM 6-14 days of infection. The colloidal gold method was adapted from Tanaka with modifications. Both pre- and post-embedding were used and LK4M was used for the latter. Two monoclonal antibodies (McAb-100 & 102) against the virus glycoprotein I and II were donated by Dr. Yamanishi,5 and two group specific ones (McAb-A35 & A25-1), as well as two type specific (A20 to type I, R31 to type II HFRS virus) were domestic products.
Thiamine pyrophosphatase and nucleoside diphosphatase in guinea pig pinealocytes shown by a cerium-based method
Authors: Luo Z. R. , Whitter E. F. , Schultz R. L. , McMillan P. J. 
Published: June 2020

Thiamine pyrophosphatase (TPPase) and nucleoside diphosphatase (NDPase) both have a similar localization in the endoplasmic reticulum (ER), the perinuclear space (PNS) and the Golgi apparatus (GA) in hepatocytes and other cell types. Whether they are two separate enzymes or a single one has not been determined. Recently cerium has been reported as an excellent substitute for lead. The study described here compared the activities of TPPase and NDPase in pinealocytes by the cerium-based method.Guinea pig pineal glands were fixed by perfusion with a mixture of 1% glutaraldehyde and 2% paraformaldehyde followed by immersion in the same fixative for a total of 30 min. Sections cut at 100μm on a vibratome were incubated in substrate-free incubation medium for 30 min, then for 3 hrs at room temperature in the complete medium, which contained thiamine pyrophosphate (1 mg/ml) for TPPase and inosine diphosphate (1 mg/ml) for NDPase, cerium chloride (0.7 mg/ml), manganese chloride (1 mg/ml), and 5% sucrose in buffer.
Iron storage sites in the myocardium as revealed by cytohistochemistry
Authors: Ashraf M. , Thompson F. , Miki S. , Srivastava P. 
Published: June 2020

Iron is believed to play an important role in the pathogenesis of ischemic injury. However, the sources of intracellular iron in myocytes are not yet defined. In this study we have attempted to localize iron at various cellular sites of the cardiac tissue with the ferrocyanide technique.Rat hearts were excised under ether anesthesia. They were fixed with coronary perfusion with 3% buffered glutaraldehyde made in 0.1 M cacodylate buffer pH 7.3. Sections, 60 μm in thickness, were cut on a vibratome and were incubated in the medium containing 500 mg of potassium ferrocyanide in 49.5 ml H2O and 0.5 ml concentrated HC1 for 30 minutes at room temperature. Following rinses in the buffer, tissues were dehydrated in ethanol and embedded in Spurr medium.The examination of thin sections revealed intense staining or reaction product in peroxisomes (Fig. 1).
A comparison of mass measurements with the stem using the wet-film technique with and without polylysine treatment
Authors: Simon M. N. , Shiue G. G. , Wall J. S. , Flory P. J. 
Published: June 2020

The wet film technique of injection of a specimen into a drop on a thin carbon film (for eventual freeze-drying and mass analysis in the STEM) has been described and shown to give a uniform background and, in general, good biological preservation of specimens. However, an occasional specimen either does not absorb well or is of necessity very dilute. Many specimens absorb to polylysine-treated grids nearly 10-fold better than to thin C alone. We describe here our adaptation of the polylysine treatment originally described by Williams, and our finding that polylysine-treated thin C does not give significantly worse errors in mass measurements than thin C alone.To prepare a specimen, thin C is floated off cleaved NaCl onto a dish of water. Grids covered with holey film are dropped onto the thin C. A grid is picked up, inverted and washed with water, buffer, specimen, buffer. For poly lysine grids, after washing with water, 5 μl of 10 μg/ml poly lysine is injected for 1 minute.
Low-cost digital-image processing and analysis system for on-line morphometric measurements of sem images
Authors: Rosenfeld Michael E. 
Published: June 2020

The widespread use of digital image processing systems for high resolution morphometric applications has been limited by the cost and difficulty of interfacing systems to electron microscopes. The recent development of image acquisition boards and software for PC-AT based systems and the availability of scanning electron microscopes that are capable of scanning at true TV rates (RS-170 compatible signals), have alleviated these problems. We have assembled a system consisting of a Compaq Portable 286 (Compaq Computer Corp. Houston, TX) equipped with an FG-100 image acquisition board (Imaging Technology Inc. Woburn, MA), interfaced with a Philips 515 SEM containing a motorized stage and Edax stage controller (Philips Electronics Inc. Mahwah, NJ).Utilizing commercially available software, this system has extensive image processing and morphometric analysis capabilities. For example, because TV scan rates generate images with low signal to noise ratios, improvement of the image quality is possible via real time image averaging and background subtraction using the the FG-100 board Feedback/Input lookup table.
TEM diffraction investigations of amorphous materials
Authors: Pelton A. R. 
Published: June 2020

Transmission electron microscopy has proven invaluable for studies of amorphous materials. The combination of imaging, diffraction and chemical analysis is particularily important for investigations of small volumes of mixed crystalline and amorphous alloys. Several articles have been published recently that describe imaging and EDS of metastable alloys [1-3]. The purpose of this paper is to outline the use of electron diffraction techniques to obtain both qualitative and quantitative structural information from non-crystalline materials.The SADPs in Fig.1 were taken from a study of rapidly-solidified Ti-Zr-Be metallic glasses [4,5]. Initial investigations of these alloys reported apparent evidence from calorimetry and TEM for amorphous phase separation [4]. The images from that study were characteristic of crystalline alloys that undergo spinodal decomposition. However, more recent investigations of the same alloys were able to show conclusively that the “amorphous spinodal” microstructures were actually due to thin-foil artifacts [5].
The formation and recrystallization of amorphous zones produced in GaAS by ion irradiation
Authors: Bench M. W. , Robertson I. M. , Kirk M. A. 
Published: June 2020

Transmission electron microscopy experiments have been performed to investigate the lattice damage created by heavy-ion bombardments in GaAs. These experiments were undertaken to provide additional insight into the mechanisms by which individual amorphous zones and eventually amorphous layers are created. To understand these mechanisms, the structure of the defects created as a function of material, irradiating ion, dose, dose rate, and implantation tenperature have been studied using TEM. Also, the recovery of the crystalline structure by annealing has been investigated.These experiments were performed at the High-Voltage Electron Microscope - Ion Accelerator Facility at Argonne National Laboratory. This facility consists of an HVEM which has been interfaced with two ion accelerators. This coupling, plus the availability of several specimen stages permits ion irradiations to be performed in the specimen chamber of the microscope at controlled temperatures from 10 to 1000 K.
Evaluation of amorphous and crystalline SiC by extended energy loss fine structure (EXELFS) analysis
Authors: Angelini P. , Sklad P. S. , Sevely J. C. , Hssein D. K. 
Published: June 2020

Crystalline as well as amorphous forms of silicon carbide are materials which have important uses in many areas of materials science including structural ceramics, coatings, and semiconductors. The characterization of SiC by the use of the EXELFS technique yields radial distribution functions (RDF) which are sensitive to the structure and composition within near neighbor distances of either C or Si atoms. In this way a quantitative analysis of possible variations in “structure” can be made. EXELFS analyses of crystalline SiC are especially important in order to evaluate the method when comparison with results from the amorphous state are to be made. The EXELFS technique has previously been applied to study both crystalline as well as amorphous materials.Crystalline as well as amorphous SiC was evaluated. One specimen was a commercially available SiC single crystal. Two other specimens utilized a similar SiC starting material which had been made amorphous either by ion implantation with chromium or by irradiation from 300 kV electrons.
Ion beam stimulated reactions in metallic alloys
Authors: Mansur L. K. , Lee E. H. 
Published: June 2020

Ion implantation, ion beam mixing, and ion beam stimulated reactions can be discussed as somewhat distinct but related processes. The first two emphasize compositional changes in near-surface regions. The last relies mainly on microstructural and precipitation reactions caused by atomic displacements. In this last area much of the work has been carried out in metallic alloys. Here we summarize experiments in our laboratory that cover several ion-beam-induced reactions in Fe-15Ni-15Cr base alloys, to provide a perspective on related work in materials other than silicon. The techniques and mechanistic interpretations of results are applicable to a variety of materials.This is a powerful way to examine the interplay of characteristic relaxation times. Intervals of high point defect production and resultant processes, such as solute segregation and drift-directed clustering, are alternated with thermal annealing. Remarkable changes with respect to either steady bombardment or thermal aging at the same temperature can be produced. Figure 1(a) shows theoretically calculated fluctuating vacancy concentration in a steady irradiation.
Boron Precipitation and misfit dislocation structure in Si(Ge,B) buried epitaxial layers
Authors: Kola R.R. , Posthill J.B. , Rozgonyi G.A. 
Published: June 2020

Heavily boron-doped silicon buried epitaxial layers are becoming increasingly important in the fabrication of thin membranes, three dimensional structures in silicon and latch-up free CMOS circuits. Si(Ge,B) co-doping has been utilized to compensate the B-induced lattice contraction in Si and hence buried high conducting layers which are strain-free and lattice matched to the Si substrate have been realized. The utilization of isoelectronic Ge also alters the point defect distribution in silicon resulting in reduced dopant diffusion which is an added advantage in realizing shallow junctions and reduced interfacial transition width in epitaxial layers. This contribution addresses the evolution of misfit dislocation structure and B precipitation behavior in heavily B-doped buried Si epitaxial layers. In addition, the effect of Ge co-doping on B solubility in Si will be discussed.Silicon epitaxial layers were grown at 1080°C by chemical vapor deposition on 4-inch diameter p-type (100) substrates (10 and 0.04 Ω-cm) employing the SiH2Cl2-B2H6-GeH4-H2 chemical system. Single 5 μm thick epilayers and 2 μm buried layers with 4 μm intrinsic cap layers (10 Ω-cm) were grown.