bluuebunny/crossref_metadata_2025 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.
UV-excited fluorophore images obtained with IR excitation
Authors: Wokosin D. , Centonze V.F. , White J.G.
Published: June 2020

The widespread use of two-photon excitation fluorescence imaging has been somewhat inhibited by the necessity to use large, expensive, high-power, short-pulse lasers. These ultra-short pulse lasers are used as an excitation source in a raster scanning configuration to provide sufficient peak power density in a lens focal volume to generate detectable two-photon absorption events for rapid imaging. Biological studies often benefit from multiple fluorescent labels and multi-labelled samples often require different excitation wavelengths for adequate excitation of the various colored fluorophores. This is achieved inexpensively with the three Krypton Argon laser lines in standard confocal imaging systems, but multiple two-photon excitation lasers--if available-- would be a very expensive system. The lasers commonly used for two-photon imaging are tuneable, but this is not a non-trivial and time consuming process. The tuning range on these lasers allows good access to the blue-emitting and green-emitting fluorophores via two-photon excitation; however, we have found that a fixed-wavelength, compact,
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.
X-ray microscopy at the ALS: Partial coherent image modeling
Authors: Jochum L. , Meyer-Ilse W. , Medecki H. , Attwood D.
Published: June 2020

A Biological X-ray Microscopy Resource Center is planned to be built at the Advanced Light Source (ALS) in Berkeley. The first instrument will be the High Resolution Zone Plate Microscope (XM-1) installed at the bending magnet beam line 6.12. It will be operational in August 1994. The optical setup of this x-ray microscope is analog to a conventional visible light microscope using critical illumination (Fig. 1). Fresnel zone plates are used for both condenser and high resolution objective. The condenser zone plate illuminates the sample, and at the same time, in combination with a pinhole, acts as a monochromator providing quasi monochromatic illumination. The high resolution objective zone plate is used to create an enlarged image of the sample on a back-illuminated CCD detector. Exposure times for images with 1000 by 1000 pixels are expected to be a few seconds. In order to permit examination of the sample before and after the x-ray imaging, the design of our instrument includes two visiblelight microscopes.
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-diffraction patterns from frozen hydrate protein microcrystals: A new tool instructural studies
Authors: Burmester Christoph , Holmes Kenneth C. , Schröder Rasmus R.
Published: June 2020

Electron crystallography of 2D protein crystals can yield models with atomic resolution by taking Fourier amplitudes from electron diffraction and phase information from processed images. Imaging at atomic resolution is more difficult than the recording of corresponding electron diffraction patterns. Therefore attempts have been made to recover phase information from diffraction data from 2-D and 3-D crystals by the method of isomorphous replacement using heavy atom labelled protein crystals. These experiments, however, have so far not produced usable phase information, partly because of the large experimental error in the spot intensities. Here we present electron diffraction data obtained from frozen hydrated 3-D protein crystals with an energy-filter microscope and a specially constructed Image Plate scanner which are of considerably better crystallographic quality (as evidenced in much smaller values for the crystallographic R-factors Rsym and Rmerge) than those reported before. The quality of this data shows that the method of isomorphous replacement could indeed be used for phase determination for diffraction data obtained from 3-D microcrystals by electron diffraction.
Correlation averaging and structural changes in GP32*I crystal unit cells
Authors: Sherman Michael B. , Soejima Toshinori , van Heel Marin , Chiu Wah
Published: June 2020

We compared correlation and Fourier averaging by analyzing 400 kV spot-scan electron images of iceembedded gp32*I crystals from a previous study using correlation averaging and multivariate statistical analysis (MSA). The set consisted of 9 spot-scan electron images (Fig. 1) from different micrographs. Unit cells of gp32*I crystal in each spot-scan image were located using cross-correlation map ofthe whole image with its central portion (an area of up to 10 unit cells). Each correlation peak in the map served as a center for picking up a patch of the same size as the reference used for mapcalculation. After averaging of the patches a new reference with improved signal-to-noise ratio was obtained and procedure was iterated several times using progressively smaller reference sizes. Final reference size was about 1-2 unit cells. This permitted us to follow local lattice variations. The technique does not use any assumption of crystallinity of the specimen and can be applied for highly distorted crystal lattices. Each spot-scan image was processed independently of the others. After the iterativeprocedure a final set of averaged images was obtained and structure factor amplitudes and phases were calculated from them using standard crystallographic procedures followed by merging all the spectra. Using the set of structure factors a projection map was generated which looked very similar to the 4 Å resolution map obtained using Fourier averaging technique (Fig. 2).
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.
A correlative in vitro study of osteoblast-like cells on titanium using SEM and TEM
Authors: Krizan K. E. , Keller J. C. , Zaharias R. , Stanford C. M.
Published: June 2020

The objective of this study was to evaluate cell morphology in response to an implant model surface using SEM and TEM. Through our efforts to understand these biological responses at the ultrastructure level we hope to better define surface characteristics that encourage optimal cell surface interaction. Osteoblast-like cells were derived from rat calvaria (RCOB), plated (5 X 104 cells/10 μl micromass) on cp Titanium (Ti) discs (7.5 X 3.5 mm) and grown twelve days in CMRL media +10% FSB, 5% /3-glycerophosphate, using 5% CO2 in air. Discs were prepared by polishing with 600 grit SiC paper, cleaned, washed, passivated and UV light sterilized. At 12 days, specimens for TEM were fixed with 3% formaldehyde/ glutaraldehyde, in 0.2M cacodylate buffer, pH 7.2 and post fixed in 1% Osmium, using 1 mg/ml Ruthenium Red. Cells were en bloc stained with 2% uranyl acetate, dehydrated and routinely embedded in Spurr plastic resin. These embedded cells were separated from their Ti discs using a cryofacture technique, reembedded and sectioned with diamond knife for TEM. Cells for SEM were fixed, post fixed, dehydrated, critical point dried and coated with Carbon.
A histochemical and ultrastructural profile of a primary locomotor muscle in the common blue crab
Authors: Apostolides Lora M. , Levin Martin A. , Booth Charles E.
Published: June 2020

Crustacean muscle fibers are diverse in physiological and morphological characteristics such as contraction speed, sarcomere length, actin to myosin filament ratio, and dependence on oxidative or glycolytic metabolism. The goal of this laboratory is to examine the fiber populations in similar muscles of several species of crab to determine if varying degrees of locomotor capabilities (i.e., walking versus running, fatigue resistance, etc.) are related to fiber type diversity. The common blue crab, Callinectes sapidus, which is able to move rapidly over land and in water and migrate over long distances, is among the first crabs included in our study. The fiber heterogeneity of the depressor muscle, a primary locomotor muscle of the third pereopod of the blue crab, was examined. Fiber typing was based on histochemical studies of myofibrillar actomyosin ATPase activity, an enzyme correlated with maximum shortening velocity. Histochemical detection of the mitochondrial enzyme succinic dehydrogenase (SDH) was used to differentiate oxidative from non-oxidative fibers.
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.
Clostridial endospore attachment
Authors: Panessa-Warren B. J. , Tortora G. T. , Warren J. B.
Published: June 2020

Bacteria from the genus Clostridia, are responsible for such diseases as gas gangrene, wound infections, botulism, tetanus, pseudomembranous colitis, septicemia and nosocomial diarrhea. These anaerobic spores pose a special threat to man because they are ubiquitous, very difficult to kill, and tenaceously grow when conditions are right. This paper examines the process by which Clostridial endospores (specifically C.sporogenes ATCC 3584 and C. difficile ATCC 9689 & 43594) attach to a substrate and germinate, beginning the infective process.

C.sporogenes and C.difficile endospores were anerobically incubated at 35 C on CDC blood agar (BCDC) and Trypticase Soy agar(TSA) with 0.5% glucose (BD, Cockeysville, MD). Control and experimental plates were identically streaked with spore suspension using a 1 microliter loop. The control plates were allowed to incubate and grow undisturbed for the duration of the experiment. Attachment experiments were done by streaking plates with either C.sporogenes or C. difficile spore suspensions (initially used full strength, but subsequently diluted for colony counting), incubating these spores in the anaerobic hood (Forma Scientific, Marietta, Ohio) on pre-reduced plates for 27 min, 1 hr 39 min, 2 hr 30 min, 2hr 39 min and 6 hrs.
Ultrastructure features of the tertiary envelope in the cyst of the brine shrimp Artemia franciscana (Anostraca)
Authors: Lee Kit W. , Gouthro Mark A. , Belk Denton , Rosowski James R.
Published: June 2020

The brine shrimp is an important experimental organism in developmental biology and a key larval food in aquaculture. Morris and Afzelius established the basic ultrastructure of cyst and embryo membranes of Artemia and a subsequent report provided some additional features. A better understanding of the cyst shell structure and composition are prerequisites to elucidating the physical and biochemical processes of the hatching events. In the present study, scanning and transmission electron microscopy were used to visualize the internal features of the maternally produced pigmented tertiary envelope (TE) of the hatched brine shrimp cyst shell. This combined SEM and TEM approach revealed several previously unrecognized features.

Utah biotype cysts, from Sanders Brine Shrimp Company Inc., Ogden, Utah, U.S.A., were hatched over 24 hrs in saltwater. Hydrated cysts were fixed in 3% glutaraldehyde, post-fixed in 1% osmium tetroxide, dehydrated in an ethanol series, and critical-point dried or embedded in Epon. In some cases, the critical-point dried cyst shell was fractured before sputter-coating with gold/palladium for SEM.
Nanosurgery of biological specimens using chemically enhanced focused ion-beam etching
Authors: Mackenzie J. M. , Griffis D. P. , Russell P. E.
Published: June 2020

Many biological events occur at a small number of specific sites within a very large volume. It has recently been shown that focused ion beam (FIB) technology is useful for exposing biological structures for examination. In addition, it has been shown that biological material can be removed using FIB without detectable collateral damage beyond 100Å in fixed, dehydrated, critically point dried tissue.

The next step in determining the practical utility of FIB for removal of material from a representative tissue block is to demonstrate that relevant biological structure can be exposed at a selected site. A cross sectioning technique, commonly used for analysis of semiconductor devices, was employed to demonstrate this capability on a block of rat liver prepared as above for SEM. A contiguous-series of successively deeper rectangles are cut into the material using a relatively large, high current beam (0.18μm diameter, 1nA), removing a wedge of material and leaving a large exposed face perpendicular to the surface. The exposed face can then be examined by tilting the sample and viewing with either the FIB or by SEM.
Introduction to automated particle analysis
Authors: Vander Wood T. B.
Published: June 2020

A microscopist is presented with a special problem when asked to characterize a population of particles. In order to adequately describe the sample, it may be necessary to examine hundreds or even thousands of individual particles, recording the size, shape, identity or other parameters of interest. To manually characterize a statistically significant fraction of the sample could require many hours of tedious work at the scope, followed by still more tedious hours of data reduction. What is needed is a technique to automate the repetitive parts of this process: the recognition and characterization of particles in the sample and the reduction of data and presentation of results. This technique is automated particle analysis.

In 1968, automated particle analysis (APA) took early, tentative steps when Moore and coworkers at what was then the National Bureau of Standards demonstrated the possibility of computer analysis of images of small particles. The computing power needed for this work was massive for the day and restricted growth of the field for ten years, but in 1980, publications by Lee and others and Fritz et al.
Organic-inorganic interfaces in biological composites
Authors: Sarikaya Mehmet
Published: June 2020

Biological hard tissues, such as bone, dentin, and mollusk shells, are composite materials incorporating an organic matrix and inorganic crystallites in a complex nano- and micro-architectural forms. The interest of physical sciences in biological composites stems from the fact that these materials are self assembled in an hierarchical fashion from molecular to macro scale, and that the resulting assemblies have properties that far exceed those of current synthetic materials of similar elemental or phase compositions. The objective of biomimetics is to either mimick structures of biological composites, biomimicking, or use the synthesis methodologies of organisms to produce new materials, bioduplication. In a biocomposite, substructure and crystallography of the inorganic component are highly ordered, its morphology and shape are species specific; these are all thought to be regulated by the organic matrix. The understanding of ructural relationship between the organic and ceramic components of a biological composite, therefore, is fundamental both to the understanding of mechanisms of biomineralization and to biomimetic design and synthesis of novel engineering materials. These issues will be addressed in the present paper.
Silicification of wood-cell walls
Authors: Keckler S. E. , Dabbs D. M. , Yao N. , Aksay I. A.
Published: June 2020

Cellular organic structures such as wood can be used as scaffolds for the synthesis of complex structures of organic/ceramic nanocomposites. The wood cell is a fiber-reinforced resin composite of cellulose fibers in a lignin matrix. A single cell wall, containing several layers of different fiber orientations and lignin content, is separated from its neighboring wall by the middle lamella, a lignin-rich region. In order to achieve total mineralization, deposition on and in the cell wall must be achieved. Geological fossilization of wood occurs as permineralization (filling the void spaces with mineral) and petrifaction (mineralizing the cell wall as the organic component decays) through infiltration of wood with inorganics after growth. Conversely, living plants can incorporate inorganics into their cells and in some cases into the cell walls during growth. In a recent study, we mimicked geological fossilization by infiltrating inorganic precursors into wood cells in order to enhance the properties of wood. In the current work, we use electron microscopy to examine the structure of silica formed in the cell walls after infiltration of tetraethoxysilane (TEOS).
Studying the mechanism of Lα/HII and Lα/QII phase transmissions in phospholipid liquid crystals with temperature-jump cryo-TEM
Authors: Siegel D. P. , Green W. J. , Talmon Y.
Published: June 2020

The transitions between lamellar (Lα), inverted cubic (QII), and inverted hexagonal (HII) liquid crystalline phases can be very rapid, despite drastic changes in system topology. The Lα phase is a stack of flat lipid bilayers, the HII phase is a hexagonal array of inverted rod micelles, and the QII phase is a lipid bilayer labyrinth with the geometry of an infinite periodic minimal surface. The mechanism of the transitions from the Lα a phase are of particular interest: they start with interbilayer events that are related to the process of biomembrane fusion, a ubiquitous and essential process in cellular function. Previous theoretical work suggested two possible mechanisms for these transitions. We have studied these transitions using time-resolved cryo-TEM. Earlier, we used on-the-grid mixing techniques to trigger the transition and observe some of the intermediates that form within seconds. Here we use a novel temperature-jump cryo-TEM technique which triggers the phase transition several milliseconds before vitrification. We extend the initial results obtained with this apparatus and reinterpret them in terms of a new theory of the transition mechanism.
SEM evaluation of pacemaker surface processing
Authors: Pettman Ray , Okerstrom Susan
Published: June 2020

Surface condition is critical for pacemakers (fig. 1) and other implanted biomedical devices. The surface must be cleanable, sterilizable, non-irritating to tissues, and have a good cosmetic appearance. Pure titanium is used for the pacemaker shields to enclose the circuitry. Current techniques for finishing the shields center around bright mill rolling and subsequent straight line finishing (SLF) or buffing. Small defects are magnified during buffing while SLF (fig. 2) fractures and galls the surface.

A study was done to optimize surface finishing of pacemakers. Early efforts utilized three grits in a sandblasting technique. They were aluminum oxide ( A12O3), figure 3, zirconium oxide (ZrO2), figure 4, and silicon oxide (SiO2), figure 5. Standard light microscopy was employed to assess these first attempts. The resulting surfaces from the blasting mediums looked very similar. Standard light microscopy lacked the depth of field, magnification and resolution to adequately perform this analysis. Scanning electron microscopy (SEM) showed greater differences between the surface treatments.
Template mediated crystal engineering
Authors: Heywood Brigid R. , Champ S.
Published: June 2020

Recent work on the crystallisation of inorganic crystals under compressed monomolecular surfactant films has shown that two dimensional templates can be used to promote the oriented nucleation of solids. When a suitable long alkyl chain surfactant is cast on the crystallisation media a monodispersied population of crystals forms exclusively at the monolayer/solution interface. Each crystal is aligned with a specific crystallographic axis perpendicular to the plane of the monolayer suggesting that nucleation is facilitated by recognition events between the nascent inorganic solid and the organic template.

For example, monolayers of the long alkyl chain surfactant, stearic acid will promote the oriented nucleation of the calcium carbonate polymorph, calcite, on the (100) face, whereas compressed monolayers of n-eicosyl sulphate will induce calcite nucleation on the (001) face, (Figure 1 & 2). An extensive program of research has confirmed the general principle that molecular recognition events at the interface (including electrostatic interactions, geometric homology, stereochemical complementarity) can be used to promote the crystal engineering process.
Automated asbestos analysis with Philips CM microscopes
Authors: Felsmann Michael , Otten Max T.
Published: June 2020

The analysis of asbestos fibres is well established (see 1 for a description of the preparation and the procedure for detection and fibre characterisation with a transmission microscope). Although the procedure for fibre counting and characterisation is described in detail, the result depends on the accuracy of the time-consuming and tedious sample inspection. A substantial part of operator effort is wasted on scanning the grid in the right way in order to avoid double counting of fibres or missingareas. In this way a subjective factor may contribute to the measurement and can distort the results.

In order to make asbestos analysis more reliable, a remote control program has been developed for the motorised goniometers of the Philips CM series microscopes (the CompuStage of the recently introduced Cmxxx series or the Specimen Relocation System of the previous Cmxx series). The program controls the systematic scanning of the grid and documentation of the fibres detected. In this way the operator can concentrate fully on the inspection and characterisation of the fibres.
The need of electron microscopy in the study of domains and domain walls in ferroelectrics
Authors: Cao Wenwu
Published: June 2020

Domain structures play a key role in determining the physical properties of ferroelectric materials. The formation of these ferroelectric domains and domain walls are determined by the intrinsic nonlinearity and the nonlocal coupling of the polarization. Analogous to soliton excitations, domain walls can have high mobility when the domain wall energy is high. The domain wall can be describes by a continuum theory owning to the long range nature of the dipole-dipole interactions in ferroelectrics. The simplest form for the Landau energy is the so called ϕ model which can be used to describe a second order phase transition from a cubic prototype,

where Pi (i =1, 2, 3) are the components of polarization vector, α's are the linear and nonlinear dielectric constants. In order to take into account the nonlocal coupling, a gradient energy should be included, for cubic symmetry the gradient energy is given by,
The structure and distribution of 90° domains in PbTiO3 ferroelectric thin films
Authors: Streiffer S. K. , Stemmer S. , Hsu W.-Y. , Ernst F. , Raj R. , Rühle M.
Published: June 2020

Many properties of perovskite-derived, tetragonal, ferroelectric thin films, such as saturation polarization and coefficient of second harmonic generation, have proven to be a strong function of the volume fraction of material oriented with its c-axis approximately perpendicular to the plane of the substrate, the so-called a-domains. Films are typically deposited above their Curie temperature, and a-domains form during cooling after growth in order to relieve strains generated by the transformation of the material from the high-temperature cubic phase to the ferroelectric, tetragonal modification. Models based on free-energy considerations of this twinning transformation under the constraints imposed by a rigid substrate have been proposed which predict a-domain widths and volume fractions as a function of e.g., film thickness and epitaxial and thermal expansion mismatch with the substrate.

We have used transmission electron microscopy to examine the intrinsic factors influencing the size and distribution of a-domains in epitaxial PbTiO3 ferroelectric thin films grown by laser ablation.
Epitaxial growth of PbTiO3 thin films on {100} SrTiO3 from solution precursors
Authors: Seifert Andreas
Published: June 2020

A mixed Pb-Ti-alkoxide liquid precursor, prepared from lead acetate and titanium iso-propoxide was used to form single crystal PbTiO3 thin films epitaxially on {100} SrTiO3 substrates.

A gravimetric analysis of the precursor determined its molarity to 0.55 mol/1 and was carried out by drying the alkoxide overnight and heating it to 600° C for one hour. X-ray diffraction showed the resulting PbTiO3 powder to be single phase perovskite. PbTiO3 thin films were formed by spincoating previously annealed (1400°C, 2h) single crystal SrTiO3 substrates. During this process the precursor dries to a gel-like amorphous solid film that pyrolizes and crystallizes to the oxide during heat-treatment. XRD, SEM, TEM and AFM were used to characterize the progress of the epitaxial layer formation as well as the microstructural evolution of films heated at increasing temperatures, ranging from 400°C to 800°C. For XRD Θ-2Θ scans on PbTiO3 thin films heated at temperatures of 450°C and above, only the {00l} tetragonal PbTiO3 reflections (CPTO=0.4153 nm) could be observed, indicating strongly oriented or epitaxial films ({h00} of PbTiO3 (aPTO=0.3899 nm) is masked by (MX)} of the SrTiO3 substrate (aSTO=0.3904 nm)).