bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
Ultrastructural diagnosis of peritoneal malignant mesothelioma
Authors: Siew S. 
Published: June 2020

Mesothelial cells constitute the lining of the three serous sacs of the body i.e. the pleura, pericardium and peritoneum. The more common type of malignant neoplasia of the serous sacs is seeding by metastatic tumors and primary malignancy of the mesothelium is unusual. Of the three sacs, the pleura is the most common site of malignant mesothelioma. Involvement of the peritoneum is extremely rare.We report 3 cases of malignant mesothelioma of the peritoneum. All of them were female. Their ages were 57, 67 and 72 years, respectively. The patients presented with abdominal discomfort and/or ascites. The extent of the tumors ranged from a peritoneal implant to widespread infiltration of the peritoneum and omentum. Histologic examination in Case 1 showed the presence of a diffusely infiltrating papillary mesothelioma without a sarcomatoid component. A mesodermal element was present in the other two cases. In order to establish a morphological diagnosis of malignant mesothelioma, the possibility has to be excluded of a metastatic adenocarcinoma.
Ultrastructural evidence for bladder MAST cell degranulation and their imminent association with nerve fibers in patients with interstitial cystitis
Authors: He F. , Hofmeister M. , Ratliff T. , Becich M. 
Published: June 2020

The ultrastructure of human mast cells (HMCs) in various diseases has been well documented; however, detailed morphological description of human bladder mast cells (HBMCs) in patients with interstitial cystitis (IC) is incomplete. The present study was undertaken to reveal any morphological modifications of human bladder mast cells (HBMCs) from the IC patients and to investigate the spatial relationships between nerve fibers and these mast cells at the ultrastructural level.Fresh-fixed surgical biopsy specimens from IC patients as well as paraffin blocks of IC retrieved through our medical record archival system were processed with routine and deparaffinization methods for transmission electron microscopy (1). No differences in mast cell morphology were noticed between the fresh-fixed or paraffin embedded tissues.The general electron microscopic appearances of the HBMCs in IC located in both mucosa and muscle layers were similar to those of HMCs observed in other sites where mastocytosis may occur due to various pathological processes (Fig. 1).
Use of thin sections and freeze-etch replicas to differentiate the macrogametocyte from the microgametocyte in the malarial parasite Plasmodium falciparum
Authors: Meszoely Charles A. M. , Venugopal Devi , Erbe Eric F. , Wergin William P. 
Published: June 2020

Gametocytes of Plasmodium falciparum grown in culture were chemically fixed in 2% glutaraldehyde. For observation of thin sections, specimens were postfixed in 1 % osmium tetroxide, dehydrated in ethanol, and embedded in resin. Thin sections were stained with uranyl acetate and lead citrate and examined with a Zeiss EM-10 transmission electron microscope (TEM). For observations of freeze-etched replicas, specimens were cryoprotected in 30% glycerol, fractured, etched, shadowed and coated in a modified Denton DFE-2 module. The replicas were examined with a JEOL JEM 100-B TEM.Previous ultrastructural studies on the gametocytes of many species of Plasmodium compared and contrasted the pellicular complex and cytoplasmic organelles, but differentiation of the macrogametocyte and the microgametocyte in freeze-etched preparations has not been reported. The intraerythrocytic macro- and microgametocytes can be easily differentiated by their staining properties in Giemsa stained preparations examined by light microscopy. The present study, using thin sectioning and freeze-etching techniques, differentiates the macrogametocyte from the microgametocyte of Plasmodium (Laverania) falciparum (Welch, 1897) by characterizing their cytoplasmic organelles.
Localization of cell-surface and basement-membrane heparan-sulfate proteoglycans using the malaria circumsporozoite protein
Authors: Frevert U. , Sinnis S. , Cerami C. , Nussenzweig V. 
Published: June 2020

Malaria sporozoites, which invade hepatocytes within minutes after transmission by an infected mosquito, are covered with the circumsporozoite (CS) protein, which in all Plasmodium species contains the conserved region II-plus. This region is also found as a cell-adhesive motif in a variety of host proteins like thrombospondin, properdin and the terminal complement components.The CS protein with its region II-plus specifically binds to heparan sulfate proteoglycans (HSPG) on the basolateral surface of hepatocytes in the space of Disse (FIG. 1), to certain basolateral cell membranes and basement membranes of the kidney (FIG. 2) as well as to heparin in the granules of connective tissue mast cells. The distribution of the HSPG receptors for the CS protein was examined by incubation of Lowicryl K4M or LR White sections of liver and kidney tissue with the recombinant CS ligand, whose binding sites were detected with a monoclonal anti-CS antibody and protein A gold.
An immunocytochemical, cytosol, and ultrastructural study of tissue ferritin in breast carcinoma
Authors: Elliott Robert L. , Wang Fen , Elliott Mary C. , Head Jonathan F. 
Published: June 2020

Increased levels of serum ferritin in breast carcinoma is well known, however, its exact source has been disputed. Weinstein et al found six times the ferritin concentration in malignant tissue as compared to benign tissue. The anaplastic tumors had the highest ferritin concentrations, suggesting that the major site of the increased ferritin was the malignant epithelium. We found in a previous cytosolic and electron microscopic study of tissue ferritin in breast carcinoma that the malignant epithelium is almost certainly the source of the increased ferritin.To better define and expand this study and increase our knowledge of the role of transferrin receptors and iron metabolism in breast cancer, we began an immunocytochemical study of tissue ferritin to compliment our cytosol and ultrastructural observations. This was done with a mouse antihuman ferritin monoclonal antibody. To date 92 specimens have been examined by all three techniques. Immunocytochemical tissue slides showed intense staining of the cytoplasm with immunoperoxidase, and the intensity of the cytoplasmic staining correlated with the cytosolic concentrations and the electron microscopic findings.
The vascular morphology of the rabbit ureter: A corrosion-cast study
Authors: Douglas G. C. , Hossler F. E. 
Published: June 2020

The prevention of urological complications in renal homotransplantation and ureteral reconstruction requires preserving the integrity of the ureteral blood supply. Vascular insufficiency is believed to be the underlying cause of ureteral necrosis and urinary extravasation in kidney transplant surgery. However, the ureteral vasculature has been described primarily at the gross level. Because of its critical role in the success of renal transplants and its potential vulnerability to surgical trauma, the ureteral vasculature deserves a more detailed investigation.We studied the ureteral vasculature (UV) in 29 male New Zealand rabbits using routine light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) of vascular corrosion casts. After cannulation of the abdominal aorta, the UV was perfuse fixed with buffered glutaraldehyde, embedded, and cut into thin sections for LM and TEM. For corrosion casting the UV was perfused with buffered saline and filled with resin (Mercox®/methylmethacrylate, 4/1) at physiological temperature and pressure. Cast tissues were macerated with 10% KOH, washed in water, critical point dried, and mounted with silver paste for routine SEM examination.
Atomic-Force Microscopy techniques for imaging cells and biological macromolecules in solution
Authors: Marchese-Ragona Silvio P. , Christie Briggs , Bucher Roland 
Published: June 2020

The Atomic Force Microscope (AFM) is increasingly being used in the Life-Sciences field. With this increase in usage there has occurred a concomitant increase in the need for both better developed specimen preparation techniques and better defined operational parameters for the AFM instrument. Life-Science AFM methodology can be divided in to three main areas:Support substrate for the Specimen,Immobilization techniques for attaching the specimen to the support substrate, andOptimum instrument scan parameters to ensure reliable transfer of data from the specimen to the image.Of central importance to Life-Science AFM is the nature of the substrate to be used. The most reliable substrates are those with a well documented surface, whose features are at least an order of magnitude smaller than the specimens of interest. Furthermore, the material should be transparent so that other forms of microscopy can be used (i.e. light, fluorescence, near-field scanning optical, etc.) and the surface chemistry should be both well documented and susceptible to chemical derivitization.