bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of carbogen inhalation on tumor oxygenation: Comparison of magnetic resonance and oxygen electrode measurements
Authors: Karczmar G.S. , River J.N. , Al-Hallaq H.A. , Lewis M.Z. , Oikawa H. , Kovar D.A. 
Published: June 2020

Introduction:Radiotherapy is most effective in tumors in which the tissue concentration of oxygen is high. The potential of tumor oxygenating treatments (i.e., treatments which increase tumor oxygenation as an adjunct to radiotherapy; ‘TOX’s’) to substantially improve tumor response to therapy has been clearly demonstrated in animal models and in some studies of cancer patients. However, despite some initial successes, the ability of TOX‘s to help a large percentage of cancer patients has been disappointing. The reasons for this are not clear because there is currently no method which is routinely used to image the effects of TOX‘s on tumor oxygenation with high resolution and accuracy. Development of improved TOX‘s and optimization of their clinical application would be significantly advanced by such measurements.Previous work in this laboratory and other laboratories has demonstrated that Magnetic Resonance (MR) can be used to detect effects of TOX's on tumor blood oxygenation, based on the BOLD effect (blood oxygen level dependent contrast).
Immunogold-Silver Staining (IGSS) of Agarose Embedded (NCP) Bvdv-Infected Cell Suspensions
Authors: Hearne C.E. , Campen H. Van 
Published: June 2020

The use of pre-embedding immunogold-silver staining (IGSS) in electron microscopy of cell culture monolayers has been reported by various authors and its usefulness to localize antigens has been documented. Embedding cell suspensions or cell fractions for IGSS can require time-consuming centrifugation steps. Embedding cell suspensions in agarose simplifies IGSS processing and embedding procedures.Bovine turbinate cells (BTs) were grown to confluence in 25cm3culture flasks. BTs were infected with a non-cytopathic strain (ncp) of bovine viral diarrhea virus (BVDV) while control cells were sham inoculated. At 18 h pi, cells were detached with trypsin. All following procedures were carried out at RT. The cells were fixed for 30 min in 2.0% paraformaldehyde + 0.2% glutaraldehyde in 0.1 M. phosphate buffer, pH 7.4, and rinsed 3 times in 0.1 M phosphate buffer, pH 7.4 (each centrifuged for 10 min at 300g). The cells were resuspended in 1 ml of buffer, transferred to an eppendorf tube and centrifuged for 10 min at 300g. The excess buffer was removed, 1-2 drops of warm, molten 1.0% agarose added, and the mixture centrifuged for 1 min at 300g to pellet the cells to the tip of the tube. The solidified cell-agarose mixture was removed, cut into <0.5mm3pieces, and placed in phosphate buffer.
Cryohomogenization of liver to make in vitro preparations of rough endoplasmic reticulum and other organelles
Authors: Kent Christensen A. 
Published: June 2020

Cell fractionation has been used for many years to isolate organelles for biochemical study. Typically, fresh tissue is homogenized in a suitable buffer, and the various size-classes of organelles are then isolated by differential centrifugation. One of the common fractions is the microsomal fraction, which consists largely of vesiculated rough and smooth endoplasmic reticulum, and of Golgi elements.In the past we have investigated bound polysomes on the rough endoplasmic reticulum (RER) by electron microscopy, and have used cell fractionation and EM to study the orientation of ribosomes in polysomes bound to rough microsomal vesicles. However, the value of the cell fractionation material in our work has been limited by the small size of the microsomal vesicles, which are produced by vesicular fragmentation of the endoplasmic reticulum during tissue homogenization. For our work we need in vitro preparations in which the RER retains its cisternal form, rather than being fragmented into small vesicles. This report describes a method we have devised that can yield relatively intact RER in vitro.
Visualization and analysis of capsid dimorphism in hepatitis B virus to 17 Å resolution by cryo-electron microscopy
Authors: Zlotnick A. , Cheng N. , Conway J.F. , Booy F.P. , Steven A.C. , Stahl S.J. , Wingfield P.T. 
Published: June 2020

Hepatitis B virus (HBV) is an enveloped virus with an icosahedral capsid. Its homodimeric capsid protein assembles into particles of two sizes - one with T=3 icosahedral symmetry (90 dimers), the other with T=4 symmetry (120 dimers). Both sizes of particle are found in vivo as well as in expression systems. We have developed an in vitro assembly system using purified, bacterially expressed, capsid proteins. Capsids assembled from different protein constructs were studied by cryo-electron microscopy using a Philips CM20 microscope equipped with a field emission gun operating at 120 keV.Capsids assembled from the different protein constructs were assayed by cryo-electron microscopy and sucrose gradient fractionation. Cryo-electron microscopy was required to identify the two different sizes of capsids and the small population of misshapen particles, and also to ascertain the quality of the gradient fractionation (Figure 1, 2). The protein constructs lacked the predominantly basic C-terminal 34 amino acids of the full-length capsid protein (183 amino acids), and were further truncated between residues 138 and 149. Constructs terminating between residue 140 and 149 assembled into mixtures of T=3 and T=4 particles; the smallest construct (138 residues) did not form capsids.
Nucleation of misfit and threading dislocations in GaSb/GaAs(001) heterostructure
Authors: Qian W. , Skowronski M. , Kaspi R. , De Graef M. 
Published: June 2020

GaSb thin film grown on GaAs is a promising substrate for fabrication of electronic and optical devices such as infrared photodetectors. However, these two materials exhibit a 7.8% lattice constant mismatch which raises concerns about the amount of extended defects introduced during strain relaxation. It was found that, unlike small lattice mismatched systems such as InxGa1-xAs/GaAs or GexSi1-x/Si(100), the GaSb/GaAs interface consists of a quasi-periodic array of 90° misfit dislocations, and the threading dislocation density is low despite its large lattice mismatch. This paper reports on the initial stages of GaSb growth on GaAs(001) substrates by molecular beam epitaxy (MBE). In particular, we discuss the possible formation mechanism of misfit dislocations at the GaSb/GaAs(001) interface and the origin of threading dislocations in the GaSb epilayer.GaSb thin films with nominal thicknesses of 5 to 100 nm were grown on GaAs(001) by MBE at a growth rate of about 0.8 monolayers per second.
Cross-sectional time-resolved high-resolution electron microscopy of epitaxial growth of Au on MgO
Authors: Kizuka T. , Tanaka N. 
Published: June 2020

Vapor phase epitaxial growth techniques are indispensable for production of thin film electric devices. Various structural analyses have been attempted to evaluate the epitaxial growth. Conventional transmission electron microscopy (CTEM) is a most useful method. In particular, it is known that a plan-view time-resolved CTEM of in-situ vacuum-deposition in a microscope can analyze each process of epitaxial growth. The nucleation in vacuum-deposition was also in-situ observed by a time-resolved high resolution electron microscopy (TRHREM). However many unresolved problems still remain in the studies of the epitaxial growth because it is difficult to observe the epitaxial interfaces less than a few nanometer under appropriate conditions. Much more advanced techniques are required for electron microscopy to obtain detailed information.In the present study, a TRHREM for the cross-sectional observation was developed to elucidate the epitaxial growth process in vacuum-deposition.Gold (Au) was vacuum-deposited on (001) surfaces of the magnesium oxide (MgO) substrates at room temperature in a specimen chamber of a 200-kV high-resolution electron microscope (JEOL, JEM2010).
High-resolution observations of metastable γ’ precipitation in Al-15at.%Ag
Authors: Larcher N. V. , Solorzano I. G. 
Published: June 2020

It is currently well established that, for an Al-Ag alloy quenched from the α phase and aged within the metastable solvus, the aging sequence is: supersaturated α → GP zones → γ’ → γ (Ag2Al). While GP zones and plate-shaped γ’ are metastable phases, continuously distributed in the matrix, formation of the equilibrium phase γ takes place at grain boundaries by discontinuous precipitation (DP). The crystal structure of both γ’ and γ is hep with the following orientation relationship with respect to the fee α matrix: {0001}γ′,γ // {111}α, <1120>γ′,γ, // <110>α.The mechanisms and kinetics of continuous matrix precipitation (CMP) in dilute Al-Ag alloys have been studied in considerable detail. The quantitative description of DP kinetics, however, has received less attention. The present contribution reports the microstructural evolution resulting from aging an Al-Ag alloy with Ag content higher than those previously reported in the literature, focusing the observations of γ' plate-shaped metastable precipitates.
Three Hundred Years after Hooke and Van Leeuwenhoek: Optical Microscopy in the Twenty-First Century
Authors: Isaacson M. 
Published: June 2020

We are always trying to extend our vision through the four senses of sight, sound, touch and smell. The microscopy devised by Hooke and Van Leeuwenhoek more than three centuries ago are examples of methods used to extend our visible vision. In fact, instrument designers since then have constructed microscopes using each one of our senses to give us peeks into the microworld. When Robert Hooke took some scrapings from his teeth and viewed the bacteria in these scrapings in his primitive microscope, a whole new view of the world ensued. It would, however, have been difficult to predict how microscopy would evolve in the following centuries.I am asked now to make similar predictions. Where will optical microscopy be in a decade? In order to even attempt to answer this question with some sense of validity we must look at the prehistory and hope it allows us to extend into the future.
Identification of chromosomal actin in insect cells: Structural and functional significance
Authors: Sauman Ivo 
Published: June 2020

The non-histone proteins associated with eukaryotic nuclear chromatin are incompletely characterized and their function is poorly understood. Thirty years ago, the presence of actin in the eukaryotic nucleus was reported for first time. Since then, several biochemical studies have identified actin and myosin as significant constituents of isolated nuclear matrix from a variety of cells. The studies cited above and others make a strong case for presence of actin in nuclei, but do not implicate actin as a component of eukaryotic chromosomes.Our examination of cells associated with developing ovarian follicles of lepidopterans confirmed that under routine immunocytochemical conditions, no actin can be detected with anti-actin antibodies in the follicle cell nuclei (Fig. 1a) . However, Fig. 1b demonstrates that endonuclease pretreatment of the same preparation to remove DNA followed by anti-actin antibody staining uncovers the presence of nuclear actin. Moreover, by employing squash preparations of Drosophila salivary glands and the same endonuclease digestion, it is clear that the nuclear actin is directly associated with the polytene chromosomes (Fig. 2a,b).
Development of fluorescent probes for x-ray microscopy
Authors: Moronne M. M. , Larabell C. , Selvin P. R. , von Brenndorff A. I. 
Published: June 2020

It is only in the last few years that the complimentary development of high resolution zone plate lenses and intense, tunable, monochromatic x-ray sources has made possible the construction of soft x-ray microscopes with high resolving power. Both scanning and imaging microscopes have been produced that are capable of better than 50 nm resolution, with improvements expected to reach 20 nm in the near future. Although innovative new techniques are being explored for recognizing the unique x-ray signatures of intrinsic cellular biochemical constituents at the high resolutions provided by soft x-ray microscopes, little has been done to develop specific labeling or staining techniques. Development of such methods are important to be able to assign structure-function relationships, and to identify subcellular structures that are otherwise hidden by excess image contrast, as in the case of thick specimens.In this context, Jacobsen et al (1993) have demonstrated that an x-ray microprobe such as that provided by the scanning x-ray microscope (STXM) at the National Synchrotron Light Source (NSLS) can excite visible light fluorescence in phosphor beads and fluorochrome labeled latex spheres. Importantly, the resolution of such a system is set by the size of the x-ray beam spot and not by the wavelength of the emitted visible light.
Electron Microscopy and image analysis of nucleo-protein complexes
Authors: Egelman E. H. , Yu X. 
Published: June 2020

The RecA protein of E. coli has been shown to mediate genetic recombination, regulate its own synthesis, control the expression of other genes, act as a specific protease, form a helical polymer and have an ATPase activity, among other observed properties. The unusual filament formed by the RecA protein on DNA has not previously been shown to exist outside of bacteria. Within this filament, the 36 Å pitch of B-form DNA is extended to about 95 Å, the pitch of the RecA helix. We have now establishedthat similar nucleo-protein complexes are formed by bacteriophage and yeast proteins, and availableevidence suggests that this structure is universal across all of biology, including humans. Thus, understanding the function of the RecA protein will reveal basic mechanisms, in existence inall organisms, that are at the foundation of general genetic recombination and repair.Recombination at this moment is assuming an importance far greater than just pure biology. The association between chromosomal rearrangements and neoplasms has become stronger and stronger, and these rearrangements are most likely products of the recombinatory apparatus of the normal cell. Further, damage to DNA appears to be a major cause of cancer.
Phase refinement of copper perchlorophthalocyanine from a 0.23 nm-resolution electron micrograph using the Sayre equation
Authors: Dorset Douglas L. , Kopp Sophie , Fryer John R. , Tivol William F. , Turner James N. 
Published: June 2020

The use of direct methods of phasing for electron diffraction (ED) presents opportunities which cannot be matched with x-ray diffraction. High-resolution lattice images of thin crystals obtained on the electron microscope can provide crystallographic phases after image averaging and correction for the contrast transfer function--a procedure which has no analog for x-rays. This procedure has been used for protein crystallography, where such images are often the primary source for phase information.The method has also been used in the analysis of organic molecules.A high resolution (0.23 nm) electron microscope image of epitaxially oriented copper perchlorophthalocyanine obtained at 500 kV (Fig. 1) was used to provide a basis set of 39 phases for refinement in conjunction with a set of ED amplitudes obtained at 1200 kV (Fig 2). Portions of the image were digitized with a CCD camera and a frame-grabber and analyzed using the CRISP software package. The ED pattern was scanned using a Joyce-Loebl Mk. IIIC flatbed microdensitometer to produce integrated intensities, to which no Lorenz correction was applied.
Electron holography of polymer blends
Authors: Blackson John H. , Zhang Xiao , Joy David C. 
Published: June 2020

The characterization of polymer blend morphology by TEM often requires objectionable heavy metal staining to enhance contrast, enabling phase differentiation of materials with otherwise similar electron scattering properties. In some cases, the presence of a higher atomic number species (O, N, Cl, F, etc.) in the molecular framework of one phase provides sufficient contrast without staining. In the present example the only inherent contrast mechanism for a blend of polystyrene/polyethylene/ethylene-styrene copolymer (PS/PE/E-S) should be diffraction contrast due to the crystalline PE. Electron holography was investigated as an additional method of characterizing polymer blends.Electron holography was first described by Gabor in 1948 but did not become a practical tool until recently, due to the availability of field emission gun (FEG) TEMs equipped with an electron bi-prism. Electron holography is a wave front reconstruction process that involves hologram formation and image reconstruction. An interference pattern (hologram) between a reference electron beam (passing through vacuum) and a beam passing through the specimen contains both the amplitude and phase of the transmitted electron wave.
Imaging plasmalemma dynamics by single-particle tracking of derivatized fluorescent microspheres
Authors: Hicks Barry W. , Angelides Kimon J. 
Published: June 2020

The distribution of protein and lipid in the plasmalemma of some, and perhaps all, cells is non-homogeneous. Microdomains with compositions that are not representative of the bulk membrane exist in many cell types. This phenomenon is obligatory for spatially segregating certain functions performed by the plasma membrane. Obvious examples are concentration of neurotransmitter receptors at the synaptic gap, and voltage-dependent sodium ion channels at the nodes of Ranvier in myelinated nerve. Evidence has also emerged suggesting that lipids are capable of segregating into non homogeneous domains. A potential consequence of microdomain formation would be altered lateral mobility of components within the bilayer.Recently, nanovid microscopy was used to demonstrate that N-(fluoresceinthiocarbamoyl)- phosphatidyl ethanolamine (FITC-PE) was not constrained by diffusion barriers in fibroblasts. Colloidal gold probes conjugated to antiFITC-PE antibody were observed using DIC optics to undergo Brownian motion on the membrane surface. This study concentrated on the lamellar and super-nuclear regions of the cell membrane.
The time course of calcium deposition in shells of the barnacle(Balanus amphititre amphititre)during cyprid-juvenile metamorphosis
Authors: Wallace Nancy R. , Freudenrich Craig C. , Wilbur Karl , Ingram Peter , LeFurgey Ann 
Published: June 2020

The morphology of balanomorph barnacles during metamorphosis from the cyprid larval stage to the juvenile has been examined by light microscopy and scanning electron microscopy (SEM). The free-swimming cyprid attaches to a substrate, rotates 90° in the vertical plane, molts, and assumes the adult shape. The resulting metamorph is clad in soft cuticle and has an adult-like appearance with a mantle cavity, thorax with cirri, and incipient shell plates. At some time during the development from cyprid to juvenile, the barnacle begins to mineralize its shell, but it is not known whether calcification occurs before, during, or after ecdysis. To examine this issue, electron probe x-ray microanalysis (EPXMA) was used to detect calcium in cyprids and juveniles at various times during metamorphosis.Laboratory-raised, free-swimming cyprid larvae were allowed to settle on plastic coverslips in culture dishes of seawater. The cyprids were observed with a dissecting microscope, cryopreserved in liquid nitrogen-cooled liquid propane at various times (0-24 h) during metamorphosis, freeze dried, rotary carbon-coated, and examined with scanning electron microscopy (SEM). EPXMA dot maps were obtained in parallel for qualitative assessment of calcium and other elements in the carapace, wall, and opercular plates.
Mustard-gas skin lesion and bullous pemphigoid antigen
Authors: Petrali John P. , Oglesby Susan B. , Hamilton Tracey A. 
Published: June 2020

Human dermal exposure to the chemical warfare agent, sulfur mustard gas (HD), results in the delayed formation of fluid filled bullae which are incapacitating, persistent and slow to heal. In animal investigations, the pathology is typically described as that occurring during a prevesication period and that of a vesication period. During the first 24 hours, the pathology involves the latent lethal targeting of epidermal basal cells, a disabling of hemidesmosomes (prevesication) and a progressive inflammatory edema of the lamina lucida all contributing to the formation of characteristic lucidolytic microvesicles persisting at the dermal epidermal junction (vesication). We are now investigating possible primary or secondary HD-induced effects on extracellular adherent structural proteins of the basement membrane microenvironment which may contribute to vesication or may influence the repair process. Proteins selected for immunochemical study were laminin, type IV collagen, bullous pemphigoid antigen (BPA), fibronectin and desmosomal protein.Effects on BPA were of special interest. Its epitopes, BPA1 and BPA2, have been anatomically localized to basal cell hemidesmosomes and lamina lucida, and its role as an autoimmune antigen in the etiology of clinical bullous diseases such as bullous pemphigoid is well documented.
Skeletal muscle capillary alterations and cell infiltrate in Schistosoma mansoni parasitized mice
Authors: Tonino P. , Finol H.J. , Márquez A. , Arispe M. , Payares G. 
Published: June 2020

Most of the patients suffering from severe acute schistosomiasis present myalgias and weakness. The histopathological basis for these symptoms has not been investigated. In order to study this problem we used an animal model, the Schistosoma mansoni experimentally parasitized mice. This report is limited to describe the microvascular alterations observed.Five male NMRI albino mice were infected with Schistosoma mansoni cercariae. Animals were sacrified one and three months after infection. Samples from gastrocnemius and soleus skeletal muscles were processed by routine techniques for transmission electron microscopy and observed in a Hitachi H-500 electron microscope.Ultrastructural alterations were observed in the capillaries including widening and vacuolation of endothelial cells (Figs.1,3), occlusion of lumen, mitochondrial abnormalities and lisosomal proliferation. Surface infoldings of endothelial cell were seen (Fig. 3). A varied cell infiltration was formed by mononuclear cells as macrophages (Fig. 1), lymphocytes (Fig. 3) and mast cells (Fig. 4). Polymorphonuclear leucocytes were also seen as neutrophils (Fig. 2) and eosinophils (Fig. 5). These cells were located beside the capillaries and next to the fiber surface. Parasites were not seen into skeletal muscle.
SEM studies of comparative membrane remodeling by endocytosis in toad urinary bladders following withdrawal of ADH and MZ
Authors: Mia A. J. , Davidson A. D. , Robinson C. , Oakford L. X. , Yorio T. 
Published: June 2020

Vasopressin (ADH) and mezerein (MZ) induce transmembrane water flow through water channels inserted into the apical plasma membrane. The water channels are then recycled into the cytosol during retrieval following withdrawal of vasopressin or mezerein. Previously, we demonstrated that membrane retrieval occurs within 5 min following withdrawal ofADH or MZ even after stimulation for 15 or 10 min respectively. The apical membranes appear to undergo remodeling prior to a complete membrane restoration. The loss in microstructure are restricted to the mucosal face of the apical membrane. However, little is known about the apical membrane recycling process during probnged periods of hormone stimulation. We currently report on surface membrane remodelling in toad urinary bladders following prolonged stimulation with ADH and subsequent retrieval following removal of hormone.Toads, Bufo marinus, were doubly pithed and the urinary bladders were removed and suspended as sacs with an imposed osmotic gradient (1/10 diluted Ringer's solution). Some tissues were retained in ADH 100 mU/ml for 60 min with no change in buffer and then fixed.