bluuebunny/crossref_metadata_2025 huggingface dataset:
Seminal cytology in infertile men with chlamydia trachomatis and ureaplasma urealyticum infections. observations through electron microscopy
Authors: Gallegos A. M. G. , Díaz G. O. G. , Vazquez H. M. J. , Rositas M. R. , Ramirez B. E.
Published: June 2020

Among non gonococcic uretritis 60 % of them are caused by C. trachomatis and U. urealyticum, organisms transmited by sexual contact. These are frecuently presented like asymptomatic infections and involved a diminish sperm quality. The defects in motility and morphology of spermatozoa associated with these infections have not to date been explained clearly, although, in the case of U. urealyticum it has been shown that sperm motility is decreased by the physical adherence of the organism to the tail of the spermatozoon.

Although, some descriptions of the ultraestructure of semen in pacients with U. urealyticum and C trachomatis infections exist, there has not been a detailed description of alterations of the fine structure of the spermatozoa that can or can't be related to astenozoospermia.
The effects of cisplatin, taxol, and cisplatin plus taxol on non-specific esterase and alkaline phosphatase activity in rat kupffer cells
Authors: Johnson B. N. , Aggarwal S.K
Published: June 2020

Cisplatin (cis-diamminedichloroplatinum II) and taxol (paclitaxel) are two chemotherapeutic agents used to combat various types of cancers. Cisplatin, although effective at inhibiting cell division via cross-linking of DNA, is extremely toxic to both the liver and the kidney. Taxol, a diterpene analog, interferes with cell division by specifically binding to the beta subunit of the tubulin protein, promoting the formation of these microtubule polymers. In combination, cisplatin and taxol have proven to be more effective against ovarian cancers compared to the individual use of the respective drugs. These drugs are known to influence a variety of changes within the tissue, including activation of the murine peritoneal macrophages The effects of cisplatin, taxol, and cisplatin plus taxol on the liver Kupffer cells were studied using non-specific esterase and alkaline phosphatase as markers.
Ultrastructure of a sertoli-leydig cell tumor of the ovary
Authors: Siew S. , Katlein S.
Published: June 2020

Sertoli-Leydig cell tumors of the ovary are comparatively rare, comprising less than 0.1% of ovarian neoplasms. It has been generally accepted that they are derived from remnants of primitive male directed cells of the indifferent stage of gonadal development. However, another postulate is that they originate from specialized ovarian stromal cells through different stages of differentiation. At the gross level, they tend to be nodular and solid with only focal evidence of cystic change. The histopathologic features vary with the degree of differentiation, ranging from tumors with well differentiated tubular structures lined by Sertoli cells with intertubular Leydig cells (Type I) to an undifferentiated sarcomatoid pattern (Type III) consisting of spindle shaped cells.
Cytoplasmic dynamics of the tubulin and actin cytoskeletons during teliospore germination and basidiospore formation in a rust fungus
Authors: Roberson Robert W. , Sharp William P. , Shields John P. , Sayegh Steve , Al-Anzi Bader F.
Published: June 2020

Gymnosporangium clavipes C. & P. is a basidiomycetous fungus belonging to a common and destructive group of plant pathogens known to as the rusts. The rusts are best known for their damage to economically important crops including corn, wheat, oats, and barley and have become important model organisms in cell biology studies. Of all the stages in their complex life cycle, perhaps the most interesting are those involved in teliospore germination and basidiospore formation.

As illustrated with scanning electron microscopy teliospores of G. clavipes are ellipsoidal spores consisting of an apical and basal cell (Fig. 1). Upon germination of the teliospore, four discrete morphological events occur that give rise to mature basidiospores. These events include: i) emergence of germ tubes (Fig. 2), ii) formation of three septal cross walls segmenting the germ tube into four compartments (Fig. 3), iii) growth of a single sterigma from each compartment, (Fig. 4) and iv) enlargement of sterigmal tips to form individual basidiospores (Fig. 5). The objective of this research was to determine whether these developmental stages were temporally correlated with changes in the organization of the tubulin and actin cytoskeletons.
Application of high-pressure scanning electron microscopy (ECO-SEM) in forensic sample analysis
Authors: Kubic Thomas A. , Buscaglia JoAnn
Published: June 2020

Traditionally to obtain satisfactory images and reasonable resolution with a Scanning Electron Microscope (SEM), it has been necessary to employ a high vacuum within the sample chamber.

High vacuum can result in the dehydration of materials with an alteration of sample morphology and in some cases the introduction of artifacts. In such an environment, samples that are nonconductive experience extensive charging with image degradation. Samples of forensic concern, such as textile bundles or swatches, exhibit this problem even after the application of metal coating. The problem is even more pronounced when carbon coating is used, as is often the preference of forensic microscopists in order to simplify interpretation of the EDX spectra.

The commercial availability of "high pressure" or controlled environment SEMs that operate with sample chamber pressures from 50 to 4000 millitorr, while the electron guns and columns are kept at high vacuum conditions have solved these problems. The presence of this "higher" pressure retards dehydration while charging effects are nearly eliminated.
Near-field scanning optical microscopy imaging of luminescent polymers
Authors: Kerimo J. , Vanden Bout D. A. , Higgins D. A. , Barbara P.F.
Published: June 2020

Conjugated polymers such as poly(p-pyridyl vinylene)(PPyV) have interesting photoluminescence and electroluminescence properties. These polymers have a high quantum yield of luminescence and are of great practical importance as light-emitting diodes or organic semiconductors. We have performed studies on thin films(about 50nm) of these polymers using the high spatial optical resolution of NSOM.

The luminescent polymer film was excited with 488nm light and the fluorescence was collected with a high numerical aperture microscope objective. Topography and NSOM fluorescence images were collected simultaneously and used for studying the morphology and optical properties of the film. An example of topography and fluorescence NSOM images of the film is shown in Fig. 1a. The films are very flat (2nm rms variations in topography) and have very few features. The NSOM fluorescence image shows great film inhomogeneity with bright features varying in size from 80-250nm observed throughout (Fig. 1b). These features do not correlate with the topography, indicating they may be located in the bulk of the polymer or are simply not resolvable in the topography image.
High-precision calibration of a scanning-probe microscope (SPM) for manufacturing applications
Authors: Chernoff Donald A. , Lohr Jason D. , Hansen Douglas , Lines Michael
Published: June 2020

Introduction. For ordinary SPM (Scanning Probe Microscope) work, accuracy of XYZ length measurements of about 5% is acceptable. This is accomplished by periodic calibration checks (and adjustments, if required). Measurement of critical dimensions such as feature width and spacing on integrated circuits or compact discs requires much higher accuracy. For example, the new DVD (digital video disc) standard calls for a mean track pitch of 740 nm with a maximum allowable jitter (range) of 30 nm. To achieve a range of 30 nm, the standard deviation should be 10 nm or less. According to the gage-maker's rule, the measurement tool should be 4x more precise than the object being measured, so we need a standard deviation of 2.5 nm. This report describes the combined use of a new type of calibration standard and new software to meet these requirements.

Materials. Recently, MOXTEK has produced 1- and 2-dimensional holographic gratings as calibration standards for use with SEMs (Scanning Electron Microscopes).
Spectroscopic imaging of human disease
Authors: Meyerhoff D.J.
Published: June 2020

Magnetic Resonance Imaging (MRI) observes tissue water in the presence of a magnetic field gradient to study morphological changes such as tissue volume loss and signal hyperintensities in human disease. These changes are mostly non-specific and do not appear to be correlated with the range of severity of a certain disease. In contrast, Magnetic Resonance Spectroscopy (MRS), which measures many different chemicals and tissue metabolites in the millimolar concentration range in the absence of a magnetic field gradient, has been shown to reveal characteristic metabolite patterns which are often correlated with the severity of a disease. In-vivo MRS studies are performed on widely available MRI scanners without any “sample preparation” or invasive procedures and are therefore widely used in clinical research. Hydrogen (H) MRS and MR Spectroscopic Imaging (MRSI, conceptionally a combination of MRI and MRS) measure N-acetylaspartate (a putative marker of neurons), creatine-containing metabolites (involved in energy processes in the cell), choline-containing metabolites (involved in membrane metabolism and, possibly, inflammatory processes),
Imaging free Carriers in Electronic Material using a Scanning Probe Microscope: Scanning Capacitance Microscopy
Authors: Erickson A , Adderton D , Day T , Alvis R
Published: June 2020

The development of methods to measure electrical properties, which are suitable to directly yield the desired carrier distributions on a nanometer scale has greatly benefited from the development of scanning probe technology over the last decade. Scanning Probe Microscopes (SPMs) offer inherent two-dimensionality and have been shown to have applications ranging from Magnet force to electro-chemistry. We have used an SPM in contact mode to simultaneously measure topography (and therefore physical structure) and capacitance variations (due to an applied bias) of various electronic materials such asdoped silicon, poly silicon, SiC, and III-V materials.

The technique aptly named Scanning Capacitance Microscopy (SCM) takes advantage of the fact that electrical carrier response to an applied electric field is largely dependent upon the local carrier concentration. Using a high 'Q' GHz resonant circuit, SCM measures capacitance variations due to an applied bias between the metalized nano-probe tip and semiconductor sample during scanning. Since thesevariations are directly related to dopant (carrier) concentration, the SCM generates a two-dimensional image with contrast corresponding to near-surface variations in carrier density. Because the measurement is done with an extremely sharp probe, we have been able to resolve features as small as lOnm, corresponding to attofarad (le-18 farad) capacitance changes.
TEM characterization of LPCVD Ta2O5 films fabricated by pre-deposition rapid thermal nitrtdation
Authors: Park J.C , Choi J.M. , Oh J.W. , Choi J.T. , Kim S.S. , Choi H.M. , Hahn S.B.
Published: June 2020

Chemical vapor deposited tantalum pentoxide (Ta2O5) films have been a promising dielectric material for a storage capacitor in high-density DRAM with three-dimensional cell architecture, due to its higher dielectric constant than that of conventional SiO2 or Si3N4/SiO2 films. The effective dielectric constant of Ta2O5 films is influenced by the thickness of interfacial lower-dielectric Si02 layer which could be a native oxide or a thermally grown oxide during deposition and annealing. In general, the capacitor with the thinner SiO2 layer has the larger effective dielectric constant. In this work, the capacitor structure films prepared with or without RTN treatment, which was performed to inhibit the growth of SiO2, were studied by various TEM techniques.

Two samples were prepared to compare the characteristics of the Ta2O5 films fabricated with or without RTN treatment Ta2O5 films were deposited on a phosphorus-doped polysilicon on a p-type silicon substrate by low pressure chemical vapor deposition (LPCVD).
Structure of contact sites between the outer and inner mitochondrial membranes investigated by HVEM tomography
Authors: Mannella C.A. , Buttle K.F. , O‘Farrell K.A. , Leith A. , Marko M.
Published: June 2020

Early transmission electron microscopy of plastic-embedded, thin-sectioned mitochondria indicated that there are numerous junctions between the outer and inner membranes of this organelle. More recent studies have suggested that the mitochondrial membrane contacts may be the site of protein complexes engaged in specialized functions, e.g., import of mitochondrial precursor proteins, adenine nucleotide channeling, and even intermembrane signalling. It has been suggested that the intermembrane contacts may be sites of membrane fusion involving non-bilayer lipid domains in the two membranes. However, despite growing interest in the nature and function of intramitochondrial contact sites, little is known about their structure.

We are using electron microscopic tomography with the Albany HVEM to determine the internal organization of mitochondria. We have reconstructed a 0.6-μm section through an isolated, plasticembedded rat-liver mitochondrion by combining 123 projections collected by tilting (+/- 70°) around two perpendicular tilt axes. The resulting 3-D image has confirmed the basic inner-membrane organization inferred from lower-resolution reconstructions obtained from single-axis tomography.
Microstructure of GaAs nanocrystals formed inside single crystalline silicon
Authors: Zhu Jane G. , White C. W. , Budai J. D. , Yacaman M. J. , Mondragon G.
Published: June 2020

Semiconductor nanocrystals exhibit novel properties that are important for electronic and opto-electronic device applications. Many methods have been developed to synthesize semiconductor nanocrystals. Among them is the ion implantation technique, which is compatible with the semiconductor technology. It has been recently reported that the compound semiconductor GaAs can be formed inside Si by sequential implantation of Ga and As and thermal annealing.

In this study, GaAs nanocrystals were formed by sequential implantation of As and Ga, with the same dose of 1 x 1017 cm-2, into (100) Si substrates at 550°C. The implantation energies were chosen so that the Ga and As ions are overlapped over a few hundred nanometers in depth. The samples were then annealed at 1000°C for 1 h in flowing Ar + 4%H2 atmosphere to form GaAs precipitates. Transmission electron microscopy (TEM) has been used to study the microstructures of these samples.

The cross-sectional TEM image in Fig. 1 shows the GaAs precipitates formed inside the Si substrateimplanted with As and then Ga.
Anomalous strain profiles of short-period semiconductor-superlattice structures as measured from HREM images
Authors: Robertson M.D. , Corbett J.M.
Published: June 2020

Recently, there has been considerable interest in the measurement of lattice strains at the nanometre level using high resolution electron microscopy (HREM) techniques. In particular, techniques based on the measurement of the displacements of lattice fringes from processed images derived from the individual Fourier components of the original CCD image have been successful in accurately reproducingthe strain profiles present in semiconductor and metal heterostructures. In order to isolate the information associated with a given reflection, Fourier-filter masks of approximately the first Brillouinzone in size are positioned on the desired reflection in the digital diffractogram and all the Fourier frequencies not located within the masks are removed. This procedure assumes that only information associated with a given reflection is contained within the masks. However, if Fourier information from more than one main reflection is present in the masks then artifacts may arise in the measured strain distribution.
TEM observations of hydrogen nanobubbles in implanted amorphous silicon
Authors: Jones K.M. , Williamson D.L. , Acco S. , Al-Jassim M.M.
Published: June 2020

Over the last two decades extensive studies on the optical and electrical properties of hydrogenated amorphous Si (a-Si:H) have been reported. However, less attention was given to the structural characterization of this material partly due to the insensitivity to hydrogen of structural probes such as x-rays and electron diffraction. From a recent set of experiments, results on the solubility limit of hydrogen in a special type of a-Si:H and the characterization of hydrogen induced complexes or nanobubbles has been reported. In this study, we report TEM observations of the structural morphology ofhydrogen related defects that support these recent measurements obtained by secondary ion mass spectrometry (SIMS) and small-angle x-ray scattering (SAXS).

a-Si:H thin films for solar cells and other applications are produced by a variety of methods. In each case, the deposited films are usually not homogeneous as they have been found to contain low density inhomogenities in the size range of 1-10 nm. These defects are commonly referred to as microvoids or hydrogen-rich clusters.
Electron holography of p-n junctions
Authors: Frost B.G. , Joy D.C. , Allard L.F. , Voelkl E.
Published: June 2020

A wide holographic field of view (up to 15 μm in the Hitachi-HF2000) is achieved in a TEM by switching off the objective lens and imaging the sample by the first intermediate lens. Fig.1 shows the corresponding ray diagram for low magnification image plane off-axis holography. A coherent electron beam modulated by the sample in its amplitude and its phase is superimposed on a plane reference wave by a negatively biased Möllenstedt-type biprism.

Our holograms are acquired utilizing a Hitachi HF-2000 field emission electron microscope at 200 kV. Essential for holography are a field emission gun and an electron biprism. At low magnification, the excitation of each lens must be appropriately adjusted by the free lens control mode of the microscope. The holograms are acquired by a 1024 by 1024 slow-scan CCD-camera and processed by the “Holoworks” software. The hologram fringes indicate positively and negatively charged areas in a sample by the direction of the fringe bending (Fig.2).
In-situ investigation of ion-implantation effects on radiation-induced segregation in Ni-Al alloys
Authors: Giacobbe M.J. , Lam N.Q. , Okamoto P.R. , Zaluzec N.J. , Stubbins J.F.
Published: June 2020

In-situ experiments using the HVEM (high voltage electron microscope)/Tandem accelerator facility at Argonne National Laboratory were performed to determine the effects of 400-keV Zr+ and 75-keV Ne+ implantation on electron radiation-induced segregation (RIS) in Ni-9at.%Al at 550°C and 450°C, respectively. The alteration of RIS kinetics by Ne implantation was studied at two different doses. A highly-focused 900-keV electron beam, which produces a radial defect flux away from the beam center, was used to induce segregation of Al atoms in the opposite direction via the inverse-Kirkendall effect. Within the irradiated zone, Al enrichment drives the formation of γ′-Ni3Al precipitates, and the radial segregation rate of Al was monitored by measuring the growth of the precipitate zone.

When a thin film is subject to a focused, electron beam, a non uniform defect distribution is produced. The effective beam diameter, D∘, is defined by IT= I∘ (πD∘/2)2 where IT is the total electron current and I∘ is the peak electron flux.
Irradiation-induced precipitation in direct-aged alloy 625
Authors: Burke M.G. , Bajaj R.
Published: June 2020

Direct-aged alloy 625 (DA-A625) is a precipitation-hardened nickel-base superalloy with good mechanical properties and excellent corrosion resistance. Its superior stress corrosion cracking (SCC) performance makes it a candidate material for applications in light water reactors where resistance to irradiation-assisted SCC (IASCC) is important. This alloy derives its strength from the intragranular precipitation of fine DO22 – ordered γ” precipitates. These precipitates have a disc-like morphology and are crystallo-grahically related to the γ matrix such that the [001] axis of the precipitates are oriented parallel to <100> directions in the matrix. This alloy is generally solution-annealed then aged within the temperature range ~600 to 750°C. In direct-aging, the alloy is immediately aged at ~ 660°C for 80 h following hot-working. In addition to the γ° precipitates, intergranular M23C6, M7C3, M6C, or MC carbides can form in this material.
GPB zones as a precursor for S’ precipitation in Al-based matrices
Authors: Radmilovic V. , Ratkovic S. , Shiflet G.J. , Dahmen U.
Published: June 2020

In the pseudo-binary Al-Al2CuMg alloy, the Cu/Mg-rich precipitation zones (GPB) are able to cause considerable hardening of the matrix. The hardening is apparently not very sensitive to the zone size or degree of ordering. According to Silcock these zones are cylindrical, 1-2 nm in diameter and 4 nm long. They are also formed during the early stage of aging at 190°C and are followed by nucleation of S’ precipitates with {210} habit plane. Overaging occurs by the further formation and growth of S’ with a corresponding re-solution of GPB zones. Since the discovery of GP zones (reach in Cu) in Al-Cu alloys by Guinier and Preston, the structure of these zones, even at atomic level, has been studied extensively. However, there are very few studies of GPB zone structure and crystallographic relationship with Al matrix. In this paper results using atomic resolution electron microscopy on the GPB zone size, structure and crystallographic orientation relationship with Al matrix are reported.
High-resolution EM investigation about effect of stress on formation of ω-phase crystals in β-tttanium alloys
Authors: Sukedai E. , Shimoda M. , Fujita A. , Nishizawa H. , Hashimoto H.
Published: June 2020

ω-phase particles formed in β-titanium alloys (bcc structure) act important roles to their mechanical properties such as ductility and hardness. About the ductility, fine ω-phase particles in β–titanium alloys improve the ductility, because ω-phase crystals becomes nucleation sites of α-phase and it is well known that (β+α) duplex alloys have higher ductility. In the present study, the formation sites and the formation mechanism of ω-phase crystals due to external stress and aging are investigated using the conventional and high resolution electron microscopy.

A β-titanium alloy (Til5Mo5Zr) was supplied by Kobe Steel Co., and a single crystal was prepared by a zone refining method. Plates with {110} surface were cut from the crystal and were pressured hydrostatically, and stressed by rolling and tensile testing. Specimens for aging with tensile stress were also prepared from Ti20Mo polycrystals. TEM specimens from these specimens were prepared by a twin-jet electron-polishing machine. A JEM 4000EX electron microscope operated at 400k V was used for taking dark field and HREM images.
Effect of Pt content on compositional segregation in Co-Cr-P-Pt/Cr magnetic thin films
Authors: Choi J-H. , Sung C. M. , Shin K. H. , Allard L. F.
Published: June 2020

Co/Cr alloys are among the most prominent materials for ultra-high density longitudinal magnetic recording media. The recording and magnetic properties of the materials are related to their microstructure. It has been found that compositional segregation (CS) of the Co phase at the grain boundaries, and physical separation of Co/Cr phases are effective in producing low noise media due to low intergranular exchange coupling. A series of Co/Cr alloy magnetic thin films were prepared by DC sputtering and studied using high-resolution transmission electron microscopy (HRTEM) coupled with energy dispersive x-ray spectroscopy (EDS). CoxCryPzPtw/Cr alloy thin films were deposited on circumferentially textured Ni-P/Al substrate. This substrate geometry was used to get better magnetic properties without substrate bias. A Hitachi HF-2000 field emission TEM was used for imaging and to provide a 1 nm beam for high spatial resolution EDS analysis.
Volumetric rendering of 3D SIMS depth profiles
Authors: McIntyre N.S. , Kingston D.M. , van der Heide P.A.W. , Wagter M.L. , Stanley M.B. , Clarke A.H.
Published: June 2020

Dynamic secondary ion mass spectrometry (SIMS) can be used to uncover unique information about interfaces and whole structures which are “buried” within a solid. During a depth profile of a solid, a sequence of SIMS images is acquired for each element under study The sequence is correlated into a vertical “stack” which contains digitised three dimensional (3D) elemental distributions. Although such distributions are distorted by surface roughness, preferential sputtering and SIMS matrix effects, there is still considerable structural information contained in the volume and much potential for further information retrieval as the above-mentioned distorting effects are addressed

One of the major tools used to assess distributional information within the 3D volume has been visual rendering software. Using Sunvision software (Sun Microsystems Inc.) and a small workstation, images of the volume can be constructed which display pixels either in a “maximum value” perspective or in perspectives where the density of each phase can be adjusted to maximise structural detail.Several examples of the technique will be shown.
Nuclear organization of pre-mRNA splicing factors and their substrates
Authors: Huang S. , Deerinck T. J. , Ellisman M. H. , Spector D. L.
Published: June 2020

Previous studies from our laboratory as well as other laboratories have shown that a variety of pre-mRNA splicing factors are localized to a subnuclear speckled domain when mammalian cells are immunolabeled with antibodies against these pre-mRNA splicing factors. At the electron microscopic level the speckled pattern is composed of both interchromatin granule clusters and perichromatin fibrils. A large body of evidence has accumulated from both our laboratory and other laboratories which has suggested that the perichromatin fibrils represent nascent transcripts and the interchromatin granule clusters represent storage and/or assembly sites for pre-mRNA splicing factors. The majority of substrates for these splicing factors are pre-mRNAs which contain a poly(A) tail of approximately 200-300 nucleotides. During the past year we have studied the distribution of poly(A)+ RNA in the mammalian cell nucleus and its transport through nuclear pores by fluorescence and electron microscopic in situ hybridization. Poly(A)+ RNA was detected in the nucleus as a speckled pattern which we have found to totally colocalize with pre-mRNA splicing factors at interchromatin granule clusters and perichromatin fibrils.
Molecular motors and fast axonal transport
Authors: Brady S. T.
Published: June 2020

When video microscopy was first used to study fast axonal transport in isolated axoplasm from squid giant axons, a torrent of membrane traffic was seen to move in both directions. Images of membrane bounded organelles (MBOs) moving along individual microtubules (MTs) in axoplasm opened the way for characterization of the microscopic properties of fast axonal transport and led to the characterization of two molecular motors involved in fast axonal transport. The pharmacology of MBO movement ruled out previously identified molecular motors and a biochemical dissection of fast axonal transport in axoplasm demonstrated the existence of a new class of molecular motors. Subsequently, the polypeptides comprising a new class of molecular motor, kinesin, were discovered initiating a new era in the study of molecular motors and intracellular motility.

The effects of ATP analogues on fast axonal transport led to dicovery of kinesin. When the nonhydrolyzable ATP analogue, adenylyl 5′-imidodiphosphate (AMP-PNP), was perfused into isolated axoplasm, all MBOs moving in both anterograde and retrograde directions stopped moving and remained attached to MTs. Unlike the effects of AMP-PNP on myosin and dynein, inhibition by AMP-PNP was rapid even in the presence of equimolar ATP, but was reversed by excess ATP.
Metaphase chromosome DNA mass fraction is independent of species
Authors: Williams S. , Jacobsen C. , Kirz J. , Lamm S. S. , Van’t Hof J. , Zhang X.
Published: June 2020

Previous measurements of the composition of metaphase chromosomes yield values for the DNA mass fraction ranging from 15 - 32% (eg. 1), with a factor of two variation seen for chromosomes of a single species. The factors responsible for this variation are not known, but understanding them is of fundamental importance for constructing a realistic model of metaphase chromosome structure. The Scanning Transmission X-ray Microscope (STXM) provides the ability to make quantitative measurements of unstained, unfixed, thick wet specimens with a resolution of 55 nm. We have used the STXM to measure the total mass, density, size and shape of fixed wet chromosomes from three plant species and one marsupial species with differing amounts of DNA per chromosome. These measurements allow us to determine the dependence of chromosome composition on the amount of DNA per chromosome, and to determine whether chromosome composition differs between the plant and animal kingdoms.

Metaphase chromosomes from the broad bean Vicia faba had a measured DNA mass fraction of 0.38. This value was obtained from both wet and freezedried specimens although the size and shape of the chromosomes resulting from these different treatments varied considerably (Fig. 1). This result indicates that the DNA mass fraction value obtained is not a property of the preparation procedure. Because dry specimens are not subject to mass loss at these exposure levels, the mass results for both the wet and dry specimens is not an artifact caused by radiation damage.
Imaging of 30nm gold spheres by dark-field scanning transmission x-ray microscopy
Authors: Chapman Henry N. , Williams Shawn , Jacobsen Chris
Published: June 2020

In a scanning transmission x-ray microscope (STXM), such as that operated at the beamline X-lA at the National Synchrotron Light Source, it is possible to obtain dark-field images by blocking the undeviated transmitted photons so that only x rays scattered by the specimen are detected. Although the signal that is detected in dark-field is much weaker than the conventional bright-field signal the method offers much higher contrast of small features and the possibility of detecting small features with higher signal to noise for the same incident x-ray flux. Also, the signal depends on both the amplitude and phase of the specimen, rather than just the amplitude. One important application of dark-field x-ray microscopy is the imaging of gold-labelled biological specimens. This unites the advantages of x-ray microscopy (the ability of imaging thick biological objects, low radiation dose) with those of gold labelling (specific-site or specific-protien labelling, well documented protocols).

The x-ray microscope consists of the scanning transmission x-ray microscope, in which a zone-plate is used to focus monochromatic x rays to a probe, through which the sample is scanned.
Study of surfaces and interfaces by the maximum SPEM
Authors: Ng Waiman
Published: June 2020

Photoemission spectroscopy with synchrotron radiation is a well-established technique for analyzing the electronic and chemical properties of solids and surfaces. However, photoemission suffers from a major limitation in its application to heterogeneous systems, due to large probe size (100μm * 100μm). The development of a photoemission microscope with both high spatial and energy resolution that can overcome this limitation is thus of great interest, and it can provideunique and complementary information to other microscopy techniques. The project MAXIMUM is a scanning photoemission microscope located at the U41 undulator at the Synchrotron Radiation Center at the University of Wisconsin. The instrument is based on a multilayer-coated Schwarzschild objective, operating at 95eV, which forms a small probe on the sample. A cylindrical mirror analyzer is used to detects the photoelectrons emitted from the sample. The microscope has demonstrated spatial resolution better than 0.1μm in transmission, and electron energy resolution of 250meV has alsobeen demonstrated in photoemission ission.
Automated electron tomography and CCD spot-scan imaging of biological macromolecules
Authors: Koster A. J. , Walz J. , Ziese U. , Stoschek A. , Hegerl R. , Typke D. , Kleinz J. , Baumeister W.
Published: June 2020

Computer control of a transmission electron microscope (TEM) and digital recording of images have shown to be useful tools in recording 2D data sets of macromolecules and larger cellular structures with accurately defined imaging conditions.

3D structure of individual molecules can be obtained by electron tomography. The method requires that projection data are collected over a large range of specimen tilts. With automated electron tomography images are recorded in digital format, and lateral specimen displacement together with focus changes are automatically compensated for. Typically, with our experimental set-up, we collect 75 projections of negatively stained preparations over ±75° and 30 projections of ice-embedded molecules over ±60° with a total dose of 20-50 e/Å2.

By using the spot-scan imaging mode beam-induced movements of ice-embedded specimens are greatly reduced, thus largely avoiding the loss of resolution associated with specimen instability. With CCD spot-scan imaging the size of the spot is matched to the CCD chip (Fig. 1).
Image formation analysis of thick biological specimens using three-dimensional power-spectra of through focus series
Authors: Han Karen F.
Published: June 2020

The primary focus in our laboratory is the study of higher order chromatin structure using three dimensional electron microscope tomography. Three dimensional tomography involves the deconstruction of an object by combining multiple projection views of the object at different tilt angles, image intensities are not always accurate representations of the projected object mass density, due to the effects of electron-specimen interactions and microscope lens aberrations. Therefore, an understanding of the mechanism of image formation is important for interpreting the images. The image formation for thick biological specimens has been analyzed by using both energy filtering and Ewald sphere constructions. Surprisingly, there is a significant amount of coherent transfer for our thick specimens. The relative amount of coherent transfer is correlated with the relative proportion of elastically scattered electrons using electron energy loss spectoscopy and imaging techniques.

Electron-specimen interactions include single and multiple, elastic and inelastic scattering. Multiple and inelastic scattering events give rise to nonlinear imaging effects which complicates the interpretation of collected images.
Methylamine vanadate (nanovan) negative stain
Authors: Hainfeld James F. , Safer Daniel , Wall Joseph S. , Simon Martha , Lin Beth , Powell Richard D.
Published: June 2020

Uranyl and tungstate compounds have found favor as negative stains because of their high scattering power relative to biological molecules. However, other properties, such as specimen preservation, resistance to alterations or crystallization in the electron beam, and signal to noise (S/N) ratio, are also important. It may be that lower density materials may have advantages in these areas. A new negative stain, methylamine vanadate, CH3 NH2.VO3 ("NanoVan"), offers a near physiological pH of 8, similar to phosphotungstate (pH 7) with much smoother background. It is also very stable in the electron beam with minimal granulation at a dose of l04 el / nm2 . The resolution obtainable with vanadate appears to be comparable to uranyl at low dose, but superior at higher dose where uranyl forms coarse grains (see Fig. 1). Problems with uranyl such as unwanted positive staining and need for pH below 4 can be avoided. The lower contrast permits use of thicker stain embedment for better preservation and less flattening without excessive beam attenuation.
A new high-pressure freezing apparatus: The importance of improving cooling rates during high-pressure freezing
Authors: Studer D. , Michel M. , Hunziker E. B. , Buschmann M.
Published: June 2020

High pressure freezing is the only approach shown so far to adequately cryoimmobilise bulk biological samples. Based on freeze-fractured and freeze-substituted samples, some studies suggested that a 600(μm thick specimen could be completely vitrified. Recently electron diffraction, allowing experimental proof of vitrification, demonstrated that only samples less than 200μm thick can be vitrified. This discrepancy of the depth of vitrification (600μm vs. 200μm) led us re evaluate high pressure freezing theoretically and experimentally. We calculated the cooling rate profiles through samples of different thicknesses and surface cooling rates. We also determined the depth to which bovine articular cartilage specimens could be vitrified using an improved high pressure freezing machine.

The calculations of the cooling rates are based on Fourier’s law of heat conduction. When thermal conductivity is assumed to be constant, the cooling rate can be expressed as δT/δt=α·∇2T, where α is the thermal diffusivity (α=k/ρ·C; k=thermal conductivity; ρ=density; C=heat capacity).
Synaptic organization of vertebrate taste buds
Authors: Kinnamon J. C. , Royer S. M.
Published: June 2020

The vertebrate taste bud is an end organ specialized to detect and transduce aqueous chemical stimuli. In mammals most taste buds are located on the tongue. Lingual taste buds are typically distributed over three fields or papillae: fungiform, foliate and circumvallate papillae. Fungiform papillae are found on raised eminences near the tip of the tongue. Each fungiform papilla contains from one to several taste buds. Foliate taste buds are located in epithelial folds (foliate papillae) of the posterolateral surfaces of the tongue. In the rear of the tongue circumvallate taste buds line the walls or trenches surrounding the mushroom-shaped circumvallate (= vallate) papillae. In fish, taste buds are more widely distributed, being located on the tongue, lips, barbels, gill rakers, palatal organ and the body surface. A typical vertebrate taste bud comprises 50 to 150 spindle-shaped cells that lie atop the basal lamina of the tongue.

In most mammals, the taste bud cells can be classified as dark or light cells, based on the electron-density of their cytoplasm.
Strontium can be used as a tracer to examine calcification in the adult barnacle (Balanus amphititre amphititre)
Authors: Freudenrich Craig C. , Wallace Nancy R. , Wilbur Karl , Ingram Pete , LeFurgey Ann
Published: June 2020

Calcification in barnacles occurs at the base of each shell plate; as new CaCO3is deposited at the base, the shell grows upward. Although barnacle shell growth patterns have been characterized, the cellular calcium transport mechanisms involved in biomineralization are unknown; calcium is thought to be transported through the mineralizing epithelial cells into a limited diffusional space between the cells and the shell where calcification occurs. To follow transport of calcium in the cells and newly mineralized shell, one might consider using45Ca and autoradiography.Alternatively, electron probe x-ray microanalysis (EPXMA) imaging has better spatial resolution than autoradiography, but cannot discriminate45Ca from the stable isotope. However, in studies of mammalian bone formation using EPXMA, strontium was used successfully as a tracer for calcium. To assess whether strontium could serve as a tracer for calcium in barnacles, it was first necessary to determine if strontium could be incorporated into barnacle shells.
Silicon in rat knee joints after subcutaneous injection of dimethylpolysiloxane gel breast implant material
Authors: Greene W. B. , Raso D. S. , Willingham M. C. , Silver R. M. , Greene A. S. , Makeeff J. A.
Published: June 2020

Clinically, Electron Probe X-ray Microanalysis (EPMA) studies have detected elemental silicon (Si) in remote sites of chronic inflammation (skin, finger, knee and elbow) in patients who were previously implanted with a silicone polymer-filled breast augmentation prostheses. Subsequent biopsy material obtained from the fibrous tissue capsule surrounding the implant was found to contain abundant silicon in foamy macrophages. In the remote biopsies, the elemental silicon is believed to be derived from macrophages that originated in the connective tissue capsule.

In order to study the possible cellular distribution of silicone in an animal model, 120gm female SD rats were injected subcutaneously at the nape of the neck with 2ml of breast prothesis silicone gel (1.7% of total body weight). The injection correlates to a 0.9kg silicone prostheses implanted in a 55kg human recipient. Adjuvant arthritis was produced after 8 weeks in Si injected and control animals by the subdermal injection of 0.75 mg of heat killed Mycobacterium butyrium (MB) over the left rear knee. Si injected only, Si plus MB, MB only and untreated control animals were sacrificed by Metofane inhalation at 16, 24 and 32 week intervals and tissues were processed for routine light microscopy and TEM. Decalcified knee joints were sectioned longitudinally and sent to JEOL USA, Inc. for blind, collaborative SEM x-ray microanalysis studies.
Extracellular microtubules in aphid gut
Authors: Witkus R. , Griffin M. , Jacobs L. , Bolkhovets D. , Vernon G. M.
Published: June 2020

The presence of extracellular microtubules on the microvillar surface of the intestine of a number of aphids was noted as early as 1972. The authors stated, “At present there is little evidence as to the true nature of these extracellular microtubules. We have used the term microtubule in the broad sense.” These microtubules are smaller than cytoplasmic microtubules reported earlier.

In the present investigation we have studied the intestinal epithelium of the green pea aphid, A. pisum, using transmission electron microscopy. The epithelium consists of a single layer of pyramidal shaped cells with a striated border. In the anterior part of the intestine the striated border consists of a microlabyrinth (Fig. 1) similar to that previously described for the green peach aphid, Myzus persicae. In some regions of the microlabyrinth the microtubules are arranged at right angles to the length of the infoldings; in other regions microtubules run parallel to the length of the infoldings giving support to this structure.
Ultra structure of platelets in Asian elephants, elephas maximus
Authors: Rezaian M. , Yamashiro S.
Published: June 2020

The blood platelet, derived from megakaryocytes, and participate in the initial stages of the blood coagulation process. Although there have been a few reports presenting values for a number of blood constituents in Asian elephants (Elephas Maximus), which is now an endangered species, there is a scarcity of information available on aspects of normal fine structure of its platelet.

Blood was collected from six healthy adult asian elephants and platetlcts were prepared with method used by Gentry, et al. PGEi was added to a plasma rich in protein to a final concentration of 1μM/10ml to inhibit platelet activation. Platelets were fixed with 2.5% gluteraldehyde in 1.0 M phosphate buffer at PH 7.2. Stained with tanic acid using stenberg method, and post fixed in 2.0% osmium tetroxide in the phosphate buffer. The samples were routinely processed for transmission electron microscopy.
Ultraviolet-A1 radiation induces immediate apoptosis in a human leukemia T-cell line (Jurkat)
Authors: Thomas Delma P. , Godar Dianne E.
Published: June 2020

We previously reported that radiation from all three ultraviolet (UV) waveband regions, i.e., UVA (320-400 nm), UVB (290-320 nm), and UVC (200-290 nm) cause either immediate apoptosis (UVA1, 340-400 nm) or delayed apoptosis (UVB or UVC) in L5178Y-R murine lymphoma cells. We coined the terms immediate and delayed apoptosis to help distinguish the mechanistic differences between apoptosis and programmed cell death (or delayed apoptosis) which have been incorrectly used as synonyms. This confusion occurred primarily because these two cell death mechanisms are morphologically identical. However, kinetics can be used to discriminate between these two cell death mechanisms. Immediate apoptosis occurs within 4 h following exposure, whereas delayed apoptosis requires 20-34 h to display similar morphological changes. In this investigation, we explored the possibility that the UVA1-induced immediate apoptotic mechanism might be a common phenomenon by examining a human acute T-cell leukemia cell line (Jurkat).

Four hours following either sham- or UVAl-exposure to 250, 500, or 750 kJ/m2 (resulting in approximately 50, 80 and 90% reproductive death, respectively) from a 200 W/m2 sunlamp (>340 nm), Jurkat T-cells (clone E6-1, American Type Culture Collection, Rockville, MD) were processed for transmission electron microscopy (TEM) using a procedure described previously.
Ultrastructure of liver from rats fed polychlorinatedbiphenyl congener Number 153
Authors: Singh A. , MacLellan K. , Dykeman A. , Chu I. , Villeneuve D.C.
Published: June 2020

Our environment is contaminated due to extensive commercial use, among other substances, of polychlorinated biphenyls (PCBs) in the 1960s and 1970s. It is known that position and number of chlorine atoms on the biphenyl rings confer the degree of toxicity to PCBs, however, biological tests are needed to determine the toxic severity of the compound. The present work was conducted to decipher the toxicity of 2,2’,4,4’,5,5’-hexachlorobiphenyl, viz., PCB congener no. 153. The study is part of a comprehensive investigation to determine the toxicity of various PCB congeners.

One hundred, weanling Sprague-Dawley rats were allocated to 10 groups, each comprising 10 male or female animals. The congener was dissolved in 4% corn oil. Diets of Rat Chow contained 50, 500, 5000, and 50,000 ppb of the congener; the animals of each gender that served as controls were given Chow diets that contained the oil only. Water was available to the animals, ad libitum. The animals were euthanized 13 weeks after the onset of the experiment.
A double-label confocal imaging method for detecting the internalization of bacteria by non-phagocytic mammalian cells
Authors: Chestnut M. H. , Odioso L. L. , Otte T. E. , Hulette B.C.
Published: June 2020

Internalization by non-phagocytic mammalian cells is a key part of the life cycle of several important pathogenic bacteria. Mechanistic studies of this event often include transmission electron micrographs intended to demonstrate the presence of bacteria within the mammalian cell, but these data are often uncompelling. It is very difficult to be certain, based on the appearance and number of phospholipid membranes surrounding the bacterial cell, if it is enclosed in a vesicle, is surrounded directly by mammalian cell cytoplasm, or is merely contained within an invagination of the plasma membrane. Serial thin sections could provide the needed clarification, but are almost never presented, presumably because of the effort involved. Here we offer an alternative method, combining immunofluorescence labeling of the bacterium and fluorescence staining of the mammalian cell plasma membrane with a lipophilic dye, to visualize the internalization of bacteria by mammalian cells.

Freshly isolated human gingival epithelial cells were cultured in keratinocyle serum-free medium (KSFM). Second passage cells were seeded on coverslips and placed in 24-well plates.