bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancement of Endothelin Converting Enzyme and Endothelin Receptor Subtypes in Human Myocardium with Congestive Heart Failure
Authors: Lin J , Wei C
Published: July 2020

Endothelin-1 (ET-1) is a potent endothelial cell-drived vasoconstrictive peptide which is increased in congestive heart failure (CHF). ET-1 is converted from its precursor big ET-1 by activation of endothelin converting enzyme (ECE). ET-1 binding to ET-A receptor in vascular smooth muscle cells stimulates vasoconstriction and binding to ET-B receptor in vascular endothelial cells mediates vasodilation. In previous studies, we and others demonstrated that plasma ET-1 was significantly increased in congestive heart failure. However, the presentation and localization of endothelin converting enzyme and endothelin receptors (ET-A and ET-B) in human cardiac tissue with and without heart failure remain unclear. Therefore, the current study was designed to investigate the expression and localization of endothelin receptors and endothelin converting enzyme in human myocardium in the absence or presence of congestive heart failure.

Human atrial tissues (n=6) were obtained from normal subjects and end-stage CHF patients during cardiac transplantation. The expression of ECE, ET-A and ET-B were determined by immunohistochemical staining (IHCS).
Expression and Localization of Renal Endothelin-1, Endotehlin Receptors and Endothelin Converting Enzyme in Human Renal Biopsy with Rejection after Kidney Transplantation
Authors: Kinjo M , Papadimitriou J , Drachenberg C , Weir M R , Wei C
Published: July 2020

Endothelin (ET-1) is a potent renal and systemic vasoconstrictor and sodium regulating peptide. Endothelin synthesis in the kidney have been reported in glomerulus endothelial, epithelial and mesangial cells as well as in inner medullary collecting duct. Factors stimulating the production of endothelin include shear stress, hypoxia, vasoactive agents and cytokines. Endothelin binding to ET-A receptor in vascular smooth muscle cells stimulates vasoconstriction.

Renal graft rejection is a major problem after kidney transplantation with severe renal damage and renal vasoconstriction. We hypothesized that renal tissue level of endothelin-1, endothelin receptors and endothelin converting enzyme (ECE) may increase in renal tissue with rejection after kidney transplantation. Therefore, the current study was designed to determine the endothelin-1 and endothelin receptors (ET-A and ET-B) as well as endothelin converting enzyme level by immunohistochemical staining (IHCS) in human renal tissue with rejection after kidney transplantation.
Increasing Transforming Growth Factor Beta-1 and its Receptor Expression in Human Myocardium with End-Stage Congestive Heart Failure.
Authors: Ren S , Wei C
Published: July 2020

Transforming growth factor-beta (TGF-β) is a growth-regulating peptide that has been shown to enhance collagen production both in vivo and in vitro. The previous studies demonstrated that TGF-β 1 is present in the normal animal myocardium. However, the expression and localization of TGF-β 1 and TGF-P receptor in human myocardium remain unclear. Therefore, the present study was designed to determine the TGF-β 1 and its receptor in human myocardium in normal subjects and in patients with end-stage congestive heart failure (CHF).

Human ventricular tissues were obtained from five normal subjects and five patients with end-stage CHF during cardiac transplantation. TGF-β 1 and TGF-beta type I receptor (TGF-βRI) were determined by immunohistochemical staining (IHCS). The results of IHCS was evaluated by staining density scores (0, no staining; 1, minimal staining; 2, mild staining; 3, moderate staining; and 4, strong staining). The positive staining area (+%) in entire section was also determined.
The Actions of C-Type Natriuretic Peptide on Human Mesangial Cell Apoptosis and P53 Expression
Authors: Seta K , Wei C
Published: July 2020

C-type natriuretic peptide (CNP) of endothelial cell origin via NPR-B receptor mediates antimitogenic and vasodilatory actions. As a circulating endocrine system, CNP plays a fundamental role in cardiorenal regulation. However, the actions of CNP on renal mesangial cell apoptosis remain poorly defined. Apoptosis might plays an important role during development of renal glomerular mesangial cells pathophysiology. The mechanisms of apoptosis include p53-dependent pathway and p53-independent pathway.

The hypothesis of this study is that CNP induces apoptosis through the process involving p53 gene in human glomerular mesangial cells via natriuretic peptide biological receptor. Therefore, the current study was designed to investigate the effects of CNP on apoptosis and p53 expression in human mesangial cell in the absence or presence of CNP biological receptor antagonist.

Cultured human mesangial cells (Clontech Lab., San Diego, CA) was incubated for 24 hours in the absence or presence of CNP (10-7 M). These studies were repeated with HS 142-1 (HS, 10-5 M), a CNP biological receptor antagonist.
Enhancement of Apoptosis-Related Gene Expression in Human Renal Graft Rejection
Authors: Lau P Y , Papadimitriou J , Drachenberg C , Weir M R , Wei C
Published: July 2020

Apoptosis or programmed cell death is involved in many diseases include end-stage renal failure. Apoptosis-related genes include both stimulate genes and inhibitory gene of apoptosis. The genes which stimulate apoptosis include p53 and p21-WAF. The genes which inhibit apoptosis include bcl-2 gene family. The mechanisms of apoptosis include p53-dependend pathway and p53- independent pathway. We hypothesized that apoptosis-related genes may activate in renal graft rejection after kidney transplantation. Therefore, the present study was designed to investigate apoptosis-related gene expression and localization by immunohistochemical staining (IHCS) in human renal tissues with graft rejection and compare with that in normal human renal tissue.

Human renal biopsy (n=5) were obtained after kidney transplantation with mild and moderate renal rejection. Normal human kidney biopsy was obtained during nephrectomy. P53, p21-WAF and Bcl-2 levels in renal tissue were determined by IHCS. The results of IHCS was evaluated by IHCS staining density scores (0, no staining; 1, minimal staining; 2, mild staining; 3, moderate staining; and 4, strong staining).
Cyclosporine-Induced Apoptosis in Human Cardiomyocytes Through P53-Dependent Pathway
Authors: Kinjo M , Wei C
Published: July 2020

Cyclosporine A (CsA) is the most effective and widely used immunosuppressant drug in heart, lung and kidney transplantation. However, the effect of CsA is limited by the significant toxicity. The mechanism of CsA-induced toxicity is remaining controversial. Cellular apoptosis is being suggested as a possible mediator of CsA toxicity. To date, regarding the effects of CsA on apoptosis and apoptosis-related gene regulation in cardiomyocytes remain unclear. Therefore, the current study was designed to investigate the effect of CsA on apoptosis and apoptosis-related gene p53 expression in human cardiomyocytes. We hypothesized that CsA induces apoptosis in human cardiomyocytes through p53-dependent pathway.

Human cardiac atrial tissue was obtained from open-heart surgery (n=5). The cardiac tissue was minced and incubated in the special tissue culture system for 24 hours in the absence or presence of CsA (10-7 M). To detect the DNA fragmentation, in situ terminal deoxymucleotidyl transferase dUTP nick end labeling (TUNEL) was performed.
The Apoptotic Effect of Angiotensin II in Human Vascular Smooth Muscle Cells
Authors: Ou E , Wei C
Published: July 2020

Angiotensin II is a potent vasoconstrictor and mitogenic factor. However, the effects of angiotensin II on human vascular smooth muscle cells apoptosis remain controversial. Therefore, the current study was designed to investigate the actions of angiotensin II on human vascular smooth muscle cells apoptosis.

Human saphenous vein was obtained from coronary artery bypass surgery (n=6) and was minced and incubated in the special tissue culture system in the absence or presence of angiotensin II (10-6 to 10-12M) for 1, 2, 4, 8, 16, & 24 hours. These studies were repeated with losartan (10-6M, AT- 1 receptor antagonist) and PD-123319 (10-6M, AT-2 receptor antagonist). To detect the DNA fragmentation, in situ terminal deoxymucleotidyl transferase dUTP nick end labeling (TUNEL) and DNA agarose gel analyses were performed. An average of 1000 nuclei was analyzed for TUNEL studies.

TUNEL staining and DNA gel analysis demonstrated that angiotensin II increased apoptosis in human vascular smooth muscle cells.
Extreme Pathogens
Authors: Miller S E , Howell D N
Published: July 2020

Organisms are generally designated as “extreme” when they possess adaptations that allow them to flourish when one or more environmental parameters (e.g., temperature, ionizing radiation, oxygen, water, nutrients, inorganic ions) are at unusually high or low levels. A trade-off for this extraordinary resilience is that such organisms often grow poorly (if at all) in more conventional milieus. As a result, few of them are mammalian pathogens. (Anaerobic bacteria, which frequently thrive in the hypoxic conditions afforded by devitalized tissue, are an exception to this rule.)

A broader definition of “extremity” encompasses all organisms that occupy narrow or unusual environmental niches. In this more inclusive scheme, a wealth of viruses, bacteria, fungi, and parasites with pathogenic potential in humans can be considered extreme. These organisms often pose formidable diagnostic challenges. Many have extremely narrow host ranges, rendering passage in animals and development of model systems for infection difficult or impossible.
Detection of Opportunistic Viral Infections in Biopsy Specimens.
Authors: Chien K , Heathershaw ML , Heusser RC , Shiroishi H , Gonzalez R , Nast CC , Cohen AH
Published: July 2020

Opportunistic viral infections in immunosurpressed patients may morphologically involve only a few cells. Identifying an optimal area by LM is most important before an attempt at detection of viral particles by EM. The purpose of this communication is to emphasize unusual and important structural findings for some viruses.

BKV - BK polyomavirus latently infects renal tubular epithelial cells. Immunosuppressed patients many develop reactivation with resultant tubular cell damage and acute interstitial nephritis. Ultrastructural examination shows spherical and tubular virus particles of typical polyomavirus. Cross sections of the tubular form of this virus may contain electron dense cores (fig.l). Cells may be coinfected with HIV on rare occasions (fig.2).

JCV - JC polyomavirus is the major cause of progressive multifocal leukoencephalopathy (PML). JCV are rarely seen in reactive bizarre astrocytes. Biopsy of the tissue at the periphery of lesions of PML is likely to include JC-infected oligodendrocytes; it is important to appreciate that astrocytes, regardless of appearance, are unlikely to contain the virus.
Ultrastructural Studies of Nipah Virus, A Newly Emergent Paramyxovirus, Using Thin Section, Negative Stain, Immunogold, and in Situ Hybridization Electron Microscopy
Authors: Goldsmith Cynthia S , Whistler Toni , Rollin Pierre E , Chua Kaw Bing , Bellini William , Rota Paul , Wong K T , Daszak Peter , Ksiazek Thomas G , Zaki Sherif R
Published: July 2020

An increase in cases of acute febrile encephalitis occurred in Western Malaysia between September 1998 and May 1999, and a similar illness was reported in Singapore in March 1999. Most cases occurred in males who had been exposed to pigs, or among abattoir workers, and at least 100 deaths were reported. The illness was characterized by fever and headache, followed by drowsiness and disorientation; patients with severe cases developed seizures and coma within 24 to 48 hours. Concurrently, there were also illnesses and deaths among pigs in the same region, although the symptoms predominantly involved the respiratory system, and only a few pigs had signs of neurologic disease. From a cerebral spinal fluid specimen from a human patient, Dr. Chua and colleagues were successful in isolating a virus that was morphologically identified as belonging to the family Paramyxoviridae, and is now known as Nipah virus.
The Plain and the Ugly Prion Infected Neuronal Tissue in an Experimental Animal Model; An Electron Microscopic Study.
Authors: Milroy A M , Bouzamondo E , Ralston III H J , Prusiner S B , DeArmond S J
Published: July 2020

Transmissible encephalopathy of animals (scrapie and bovine spongiform encephalopathy) and of man (Creutzfeldt-Jacob disease, new variant Creutzfeldt-Jacob disease, Kuru, Gerstmann-Straussler-Scheinker disease and familial fatal insomnia) have been well characterized as progressive neurodegenerative diseases, often associated with spongiform degeneration, neuronal loss, reactive astrocytic gliosis and variable amyloid plaques, without any sign of an immune response or inflammatory infiltrates. Prion proteins are elements that propagate variability through multiple biologically active conformers of a host encoded sialoglycoprotein (PrPc). The agent responsible for transmissible encephalopathies is composed mainly, if not exclusively, of an isoform of PrP, designated PrPSc. Extensive information of post-mortem material has been described at the light microscopic level, where the emphasis has been on spongiform tissue and amyloid plaques. Our study provides ultrastructural observations of the central nervous system, specifically of degenerating neurons and their associated changes during the course of scrapie infection in a hamster model.
A Rickettsia in the Ovary of the Twospotted Spider Mite, Tetranychus Urticae KOCH (Acarina: Tetranychedae)
Authors: Crooker Allen R
Published: July 2020

Rickettsias are small, gram-negative Alpha Proteobacteria that are, with one exception, obligate intracellular parasites. They are found in a wide range of arthropods. Some of these bacteria are arthropod-vectored disease agents of vertebrates. For example, rickettsias are the causative agents of human typhus and Rocky Mountain spotted fever. Others, such as Wolbachia, are important manipulators of their arthropod host's reproductive capabilities and are not currently known to be disease agents of vertebrates.

Research on Wolbachia and related rickettsias has increased dramatically in recent years. Most of the attention has been focused on insects, although there are occasional reports of rickettsiae being found in isopods and mites. Most recently, the use of molecular techniques has established that Wolbachia is widespread in spider and predatory mites. However, Wolbachia or other rickettsias have not been demonstrated ultrastructurally in the spider mites. This report documents the presence of a rickettsia in the ovary of the adult female twospotted spider mite, Tetranchus urticae Koch, an economically important pest of ornamental and crop plants.
Observation of Amyloid-Like Fibers of the Sup35 Protein from Saccharomyces Cerevisiae
Authors: Bailey GW , McKernan S , Price RL , Walck SD , Charest P-M , Gauvin R , Kowal Anthony S , Scheibel Thomas , Lindquist Susan L
Published: July 2020

In the yeast Saccharomyces cerevisiae, [PST] acts as an epigenetic modifier of translation termination efficiency. [PSI+] can be passed through generations of yeast cells via changes in protein conformation rather than changes in DNA or RNA, and has thus been referred to as a yeast prion. The [PSI+] determinant is the Sup35 protein. Sup35 can exist in two states - soluble and insoluble. Soluble Sup35 functions in translation termination, but when insoluble, stop codons are read through, resulting in incorrect protein products.

Sup35 is composed of three distinct domains, N, M, and C. The N region is rich in glutamine and asparagine and is required for the [PST] phenotype to exist. M is a highly charged domain, and no specific function has been assigned to it. C is essential in yeast, as it is responsible for translation termination. The insoluble form of Sup35 has characteristics reminiscent of other prion proteins - in vitro it binds to the dye Congo Red and it exhibits apple green birefringence in polarized light.
Detection and Identification of Viruses in Economically Important Insects
Authors: Bailey GW , McKernan S , Price RL , Walck SD , Charest P-M , Gauvin R , Styer E L , Hamm J J
Published: July 2020

Economically important insects include pests of plants, animals and stored products as well as insects produced commercially (honey bees, silkworms, insects for fish bait and food for birds and zoo animals). Other insects are produced in large numbers for experimental purposes, biological control of insect pests and weeds and the production of sterile insects for population suppression. Insect viruses may affect morphology, physiology and behavior, often reducing longevity and reproductive potential. Thus insect viruses can be used as biological control agents of pest insects. Insect viruses may also interfere with the production or function of biological control agents (e.g., parasitoids and predators) and insects used for research purposes. Therefore, it is advantageous to screen commercial and research colonies and imported insects for viruses.

Electron microscopy of negatively stained specimens (NS EM) offers a relatively rapid and inexpensive means of screening populations of insects for the presence of viruses or viruslike particles and to monitor the progress of virus control programs.
Ultrastructural Analysis of Beta-Amyloid Production in Monocytes, Astrocytes, Epithelial, and Endothelial Cells Infected with Chlamydia Pneumoniae Isolated from Alzheimer Brains
Authors: Little CS , Maclntyre A , Hammond C , Venuti E , Bromke BJ , Balin BJ , Appelt DM
Published: July 2020

Previously, we uncovered evidence of an infectious agent, Chlamydia pneumoniae, associated with sporadic Alzheimer's disease (AD). We demonstrated that C. pneumoniae was present in 90% of brain materials examined from AD patients, compared with 5% in age-matched, non-AD patients. We further showed that microglia and astroglia in the CNS are host cells for the bacterium. RT-PCR analyses indicated that the bacterium is metabolically-active in the brain and could be cultured in a human monocyte cell line (THP-1). Importantly, we showed that the organism is concentrated in areas of AD-neuropathology also containing tau and beta-amyloid. The present study was designed to investigate the effects of C. pneumoniae infection on beta amyloid production in human monocytes (THP-1), astroglial (CCF-STTG1), epithelial (Hep 2), and endothelial (HBMEC) cell lines. We investigated the host pathogen relationship with C. pneumoniae and whether entities characteristic of AD neuropathology such as betaamyloid are associated directly with this infectious agent.
Using Microdensitometry and Image Analysis to Study Nuclear Cycle Events in a Plant Pathogenic Fungus
Authors: Snetselaar K , Lee S , Nguyen A , McCann M
Published: July 2020

Determining the length of the various stages of the nuclear cycle and correlating nuclear cycle events with particular aspects of cell morphology generally require the use of autoradiography. The most useful label is tritiated thymidine, because it is incorporated only into DNA. Unfortunately fungi, unlike most other organisms, do not take incorporate thymidine from medium. In the past, microspectrophotometry has been used to study fungal nuclei, but this technique measures nuclei one at a time. Recent advances in image capture and analysis software have made it possible to use the technique of photomicrodensitometry to quantify DNA in nuclei stained with fluorochromes that bind quantitatively to DNA. We are using this method to study nuclear cycle events in cells of the pathogenic fungus Ustilago maydis.

The basidiomycete fungus Ustilago maydis causes corn smut disease. This fungus is dimorphic—in addition to growing by filaments in corn plants, it can exist saprobically in a yeast-like budding stage.
Induction of Transfer Cells in XYLEM of Zinnia Elegans Treated with Cadmium
Authors: Chen C C , Chen W T , Wang S Y , Chen Y R
Published: July 2020

Cadmium and zinc are transition elements belonging to group II B in periodical table and they share similar chemical properties. However, their morphological and physiological effects on plants are quite difference. Cadmium not only consequences changes of plant structure at the light and electron microscopic levels, but also results in the induction of phytochelatin synthesis. In the present studies, The distribution of cadmium in different parts of plants was measured and its effects on plant structure were also examined.

Three to six-week-old Zinnia elegans were grown Hoagland's solution containing different concentrations of cadmium from one to two weeks. Atomic absorption spectroscopic studies showed that the distribution of cadmium was mainly in root. The accumulation of cadmium in stems was higher than that of in leaves. In leaves, the ability of cadmium accumulation in young leaves was much higher than that of old leaves.
Calcium Distribution and Accumulation in Ovules of Plumbago Zeylanica
Authors: Zhu Hua , Russell Scott D
Published: July 2020

The embryo sac (ES) of Plumbago zeylanica, unlike most other flowering plants, lacks synergidsthe cell type that usually receives the pollen tube and the male gametes. Normally, synergids store copious amounts of calcium, estimated to exceed 15% by weight; this is believed to attract pollen tubes, which penetrate the ES, and may trigger the release of the sperm cells within one of the two synergids. If high concentrations of calcium are truly required for fertilization, the ES of Plumbago should also contain significant quantities. Synergids in normal flowering plants are preprogrammed for cell death, receiving the contents of the pollen tube directly in their cells, whereas synergid-lacking angiosperms apparently do not have such an apoptotic cell in the ES. Potassium pyroantimonate labeling was used to localize principally loosely-bound calcium, because it is a relatively mobile form of the Ca2+ ion that is available for redistribution during fertilization events.
Detection of Calcium in the Adhesive Material Obtained from the Plant Pathogen Colletotrichum Graminicola'. X Ray Microanalysis (Eds) Evidences
Authors: Leite B , Ishida ML , Alves E , Pascholati SF , Sugui JA
Published: July 2020

The appressoria formation of Colletotrichum graminicola was monitored by scanning electron microscopy (SEM) coupled with an X Ray microanalysis system (EDS - Oxford Instrument LINK ISIS). Recently formed appressoria, an infection structure of plant pathogenic fungi, firmly glues itself to an artificial surface (polystyrene) as a consequence of the production of an adhesive material (AM). The nature of this material was already demonstrated to be mainly constituted of a glycoprotein (Sugui et al, PMPP, 1998). The objective of this work was to verify the involvement of divalent ions, specially calcium, in the process as whole.

The AM was isolated and purified from conidia that germinated on polystyrene Petri dishes. The primary AM was dialyzed against three liters of distilled water before being lyophilized. Subsequently, the material was placed on top of a carbon tape and observed by scanning electron microscopy under high vacuum (Fig. 1 and 2A). On the other hand, the same material was submitted to X Ray microanalysis without coating.
Room Temperature Dewetting of Polymer Thin Films Investigated by AFM and Low Voltage SEM
Authors: Leonard DN , Batchelor AD , Spontak RJ , Russell PE
Published: July 2020

Thin films (<100nm) of diblock copolymers are being investigated for various applications including templates for nanopatterning [1], electronic packaging materials, and biomedical applications. In such applications it is essential that stable defect free films be produced repeatedly. Because long and short range forces (like van der Waals) dominate thin polymer films, instabilities are introduced in the films when they are spin-coated onto hydrophobic substrates resulting in dewetting of the film from the substrate. Dewetting is initiated at a nucleation site in a metastable film leading to the formation of a dry patch and proceeds to grow by transport of material away from the nucleation site, forming a lip that surrounds the hole. Highly symmetrical structures form during progression of the dewetting process and completion of the process can be identified when all holes coalesce forming polygons outlined by droplets of the polymer film [2].
Characterizing Interfacial Fracture Toughness Using AFM
Authors: Li M , Carter CB , Hillmyer MA , Gerberich WW
Published: July 2020

Reliability of thin polymer films is strongly dependent on interfacial adhesion. This paper concerns the application of indentation combined with atomic force microscopy (AFM) for the evaluation of polymer-non-polymer adhesion. Interfacial toughness calculations have been made using AFM measurement of geometry of delaminations induced by indentation. Fracture surfaces characterized with AFM are also presented here.

The interface chosen for study is that between polystyrene (PS) and a glass substrate. Spin coating has been used to prepare PS films. PS, dissolved in toluene, was spun onto the soda-lime glass and then dried at 60°C for 3h to remove residual solvent. The thickness of the PS film was approximately 660nm. To enhance the driving force for delamination, poly(methyl methacrylate) (PMMA) overlayers were applied on top of the PS films. The PMMA overlayer, of thickness approximately 1.5 μm, was first solvent cast onto a second glass slide, floated off the glass onto deionized water, and then laid on top of a first glass substrate which had been coated with PS.
Imaging Electrochemical Controlled Chemical Gradients Using Pulsed Force Mode Atomic Force Microscopy
Authors: Fried G , Balss K , Bohn P W
Published: July 2020

The electrochemical formation of gradients in self assembled monolayers has been demonstrated recently [1]. The capacity to image these gradients provides useful information on the physical chemistry of electrochemical striping.

Imaging chemical gradients requires the ability to sense the chemical moiety on the top of the self-assembled monolayer. This has been accomplished by derivatizing an atomic force microscope (AFM) tip with molecules selected to have specific interactions with the sample in a technique known as chemical force microscopy [2]. Typical tapping mode AFM is then used to image the sample; the tip is oscillated vertically above the sample and the tip-sample interaction modulates the amplitude of the tip.

The sample adhesion, sample stiffness, and sample topography all influence the oscillation amplitude of the tip. Pulsed Force Mode (PFM) [3] is an extension for atomic force microscopes. The PFM electronics introduces a sinusoidal modulation to the z-piezo of the AFM with an amplitude between 10 to 500 nm at a user selectable frequency between 100 Hz and 2 kHz.
Performance Data of a New 2048 X 2048 Pixel Slow-Scan CCD Camera For TEM
Authors: Hiller SA , Kabius B , Probst W , Tröster H , Trendelenburg M , Crucifix C , Tröndle A
Published: July 2020

Excellent linearity and high sensitivity have made SSCs the ideal image detector for almost every TEM application. Their ability to make high quality digital images available within fraction of seconds for further evaluation and processing in a PC, have made them a non-dispensable accessory for any modern TEM. However, despite their excellent characteristics, SSCs provide a restricted number of individual image points in respect to a negative, what is considered to be the main disadvantage of this detector. To compensate for this, CCDs with 2048x2048 pixel are available since some time. SSCs using these 2kx2k CCD arrays not only provide 4 times the pixel number but also offer a lot more options people have waiting for: e. g. highly resolved low-dose or ESI images with significantly improved signal to noise ratio, or higher resolved images for diffraction analysis and holographic reconstruction.
Electron Decelerator for Improved CCD Performance In Intermediate Voltage Electron Microscopy
Authors: Downing Kenneth H , Favia Paola , Mooney E
Published: July 2020

There are many advantages of IVEMs over more conventional microscopes, all of which make it possible to obtain more accurate data at higher resolution. One significant drawback of higher accelerating voltages is degraded performance of the electron detector, a problem that is particularly serious with CCD cameras. At any voltage, one faces a tradeoff with the CCD performance between sensitivity and resolution. Electron scattering within the scintillator and its support broaden the point spread function, while the decreased scattering cross section at higher voltages decreases the light output from the scintillator. At voltages much above 100 kV these effects have been found to seriously limit CCD performance. With the trend towards electronic data collection and microscope automation, it is essential that a high performance detector be developed for the IVEM. One approach to optimizing the performance tradeoff employs lens coupling to improve resolution, at the expense of sensitivity.
Microcalorimeter EDS: Benefits and Drawbacks
Authors: Wollman D A , Newbury Dale E , Nam S W , Hilton G C , Irwin K D , Rudman D A , Deiker S , Bergren N F , Martinis John M
Published: July 2020

The commercial introduction of high-count-rate, near-room-temperature silicon drift detectors (presently available) and high-energy-resolution cryogenic microcalorimeters (forthcoming) is an exciting development in x-ray microanalysis, in which detector choices and capabilities have been essentially stable for many years. Both of these new energy-dispersive detectors promise improved capabilities for specific applications, e.g., faster EDS mapping (silicon drift detectors) and nanoscale particle analysis (microcalorimeters). In this paper, we briefly examine some of the important benefits and drawbacks of microcalorimeter EDS (μcal EDS) for x-ray microanalysis.

The primary benefit of μcal EDS over conventional semiconductor EDS is the factor of ∼ 20 improvement in energy resolution (∼ 4 eV, real-time analog signal processing), as shown in Figure 1.
Cryodetectors for High Resolution X-Ray Spectroscopy
Authors: Höhne Jens , Bühler Matthias , Hertrich Theo , Hess Uwe
Published: July 2020

Based on excellent energy resolution and single quantum detection sensitivity, cryodetectors are offering a variety of new, analytical solutions for the analysis of elementary surface compositions, especially for the analysis of light elements and very small sized structures. Cryodetectors operate typically at temperatures between 30 and 200mK and require vibration free and fully automated cooling systems in order to qualify for industrial applications. Cryodetectors are low temperature superconductors where the two most prominent types are based on microcalorimeter and tunnel diode principles. Cryodetectors are mainly employed for surface analysis applications as energy dispersive X-ray spectrometers with energy resolutions of less than 15eV, but may also be used as highly sensitive UV, VIS or even mass spectrometers in the future.

Conventional EDX detectors are semiconductors. An impinging X-ray quantum creates a number of electronhole pairs dependent on the energy of the triggering event thus allowing energy dispersive measurements. The performance limit of semiconductor detectors has almost been reached and is determined by the excitation energy necessary to create electron-hole pairs.
The Characterization of Nano Materials in the FE-SEM
Authors: Gauvin Raynald , Horny Paula
Published: July 2020

The observation of nano materials or nano phases is generally performed using Transmission Electron Microscopy (TEM) because conventional Scanning Electron Microscopes (SEM) do not have the resolution to image such small phases. Since the last decade, a new generation of microscopes is available on the market. These are the Field Emission Scanning Electron Microscope (FE-SEM) with a virtual secondary electron detector. The FE-SEM have a higher brightness allowing probe diameter smaller than 2.5 nm with incident electron energy, E0, below 5 keV. Furthermore, what gives FE-SEM outstanding resolution is the virtual secondary electron (SE) detector. The virtual SE detector is located above the objective lens and it is also named a through-the-lens (TTL) detector. Therefore, the SE images are mostly made up of all SE of type I and II, because those of type III, which are generated by the backscattered electrons in the chamber, are not collected.
Development of an Ultra-High Resolution In-Lens FESEM
Authors: Sato Mitsugu , Kageyama Kaneo , Nakagawa Mine
Published: July 2020

Aside from the electron column, there are many factors that determine image quality in an ultra high resolution Field Emission Scanning Electron Microscope (FESEM). To obtain quality images, the operator must minimize sample contamination and be able to select the appropriate signal generated from the sample surface. Hitachi has developed a new in-lens FESEM that both minimizes surface contamination and improves signal efficiency.

Sample contamination is reduced by incorporating an oil free vacuum system, consisting of a 300 1/s turbomolccular pump and a 200 1/min scroll pump. For demanding applications, an additional 50 1/s turbomolccular pump can be added to back the main high vacuum pump. Furthermore, sample contamination caused by electron beam irradiation has been reduced by employing a high speed electrostatic beam blanking system. By blanking the beam during scan retrace (flyback), the electron dose accumulated on the sample can be minimized.
Low Voltage Biological X-Ray Microanalysis: Progress and a Remaining Problem
Authors: Echlin Patrick
Published: July 2020

Experimental work in a number of research groups over the past five years have demonstrated, unequivocally, that low voltage i.e. 5kV and below, quantitative x-ray microanalysis is a valid analytical technique which can be applied to a wide range of specimens. The advantages of this approach are now generally well known and include improved image contrast, diminished bulk charging of the sample and for bulk specimens, a reduction in the size of the beam-sample interactive volume from which the x-rays are generated, and as a consequence, a considerable improvement in the microanalytical spatial resolution. In addition, low voltages ensure a sensitive surface analysis procedure which provides true topographic contrast and that in the case of light element analysis, quantitation is simplified because the atomic number (Z), absorption (A) and fluorescence (F) effects are minimised. All these advantages are improved further if one uses a field emission gun as the primary electron source.
'Secondary’ Electron Detector Design and Positioning in the Variable Pressure Scanning Electron Microscope: The Colour Option
Authors: Griffin Brendan J , Browne James R , Egerton-Warburton Louise , Drouin Dominique
Published: July 2020

The simple models for low energy secondary electron (SE) detection in the variable pressure or environmental scanning electron microscope (ESEM) describe a gas-amplified cascade from sample to detector when a conventional biased detector is used. Recent images obtained using a modified specimen current imaging approach however have suggested that at least a portion of the image is an induced field effect, in agreement with some of the early work. Our recent aim has been to investigate a range of detector designs and positions within the chamber in both the old ElectroScan E-3 model ESEM and the current generation FEI XL30 ESEM TMP. The results support the earlier observations of induced signal components being present, with even ‘negative’ or inverted images being obtained under some detector configurations due to the noise cancellation techniques used (figure 1). These results are being quantified using the DQE measurement approach to allow an objective comparison of different designs and positions. This data will be presented for the commercially available detectors and for the ‘Griffin’ grid detector under a range of operating conditions.
Space Charge Artifacts in ESEM Images: Shadowing and Contrast Reversal
Authors: Toth M , Phillips MR
Published: July 2020

The environmental scanning electron microscope (ESEM) employs a series of pressure limiting apertures and a differential pumping system to allow for electron imaging at specimen chamber pressures of up to 50 torr. Images rich in secondary electron (SE) contrast can be obtained using the gaseous secondary electron detector (GSED) or ion current (Iion) signals. The GSED and Iion signals are amplified in a gas cascade. SEs emitted from a sample are accelerated through the gas in the specimen chamber by an electric field, EGSED, produced by a positively biased electrode located in the chamber, above the specimen. The accelerated SEs give rise to a cascade ionization process that can amplify the SE signal by up to three orders of magnitude. Electrons produced in the cascade are rapidly swept to the biased electrode and are efficiently removed from the gas. Positive ions produced in the cascade drift away from the electrode with a velocity that is at least three orders of magnitude lower than that of the electrons.
ESEM Studies of Surface Phenomena in Complex Fluids
Authors: Mathews R G , Stokes D J , Donald A M
Published: July 2020

The ability of Environmental Scanning Electron Microscopy (ESEM) to provide electron images of volatile and/or insulating samples without need for sample preparation allows imaging of liquid surface at resolutions substantially beyond those obtainable with optical microscopy.

The system chosen for study was a dispersion of di-iso-heptyl-phthalate (DHP) in water, stabilised with a mixed surfactant system comprising equal masses of Tween 20 (Polyoxyethylene sorbitan monolaurate) and Span 20 (Sorbitan monolaurate) at an effective HLB of 12.75. DHP was chosen for its unsaturated electronic structure, which improves secondary electron contrast in the ESEM, and for the similarity of its density (995 kgm-3) to water. Emulsions, containing between 25 and 80 vol% DHP and 0-3 wt% surfactant were produced in a Silverson mixer fitted with an emulsor screen. Samples were placed in a brass holder on a Peltier cooling stage and cooled to 2°C.
Imaging the Probe Skirt in the Environmental SEM
Authors: Thiel BL , Bache IC , Smith P
Published: July 2020

In low vacuum scanning electron microscopes, the primary beam is partially scattered by the gas present in the specimen chamber. The development of these microscopes, in particular the so-called ‘Environmental’ SEM, was initiated when it was realized that this scattering does not necessarily compromise the imaging capabilities of the instrument. Indeed, some modern commercial instruments are capable of better than 2 nanometer resolution at gas pressures of several torr. The accepted explanation for this is as follows: The mean-free-path of the high energy primary electrons is several millimeters in one torr of water vapour (for example). Because the actual pathlength of electrons travelling through the gas is only a few millimeters, most of them do not scatter at all. Those that do scatter are supposedly distributed over a relatively large area. Thus, the probe features a high-intensity central region surrounded by a slowly decaying low-intensity skirt. High resolution imaging is possible because the signal-to-(skirt)background ratio is high.
Two-Photon Microscopy of Single Molecules
Authors: Yuste R , Majewska A , Holthoff K , Holthoff K
Published: July 2020

Two-photon excitation has enabled investigators to image living cells in highly scattering media like the central nervous system (1). We have used a custom-built two-photon microscope to image dendritic spines from living cortical pyramidal neurons. Pyramidal cells form the majority of the neuron in the mammalian cortex and they receive practically all their synaptic contacts through dendritic spines. Dendritic spines are small (<1 μm diameter) appendages that have been practically inaccessible to physiological measurements until the application of two-photon excitation to their study (2). We have concentrated in two questions:

A- Calcium compartmentalization of spines: Mechanisms of calcium decay kinetics.

Dendritic spines can compartmentalize calcium (2). Although the mechanisms of calcium influx into spines have been explored (3), it is unknown what determines the calcium decay kinetics in spines. We investigate calcium dynamics in spines from rat CA1 pyramidal neurons in slices.
The Response of Maize Protoplasts to High Intensity Illumination in Multi-Photon Fluorescence Microscopy
Authors: Lin B L , Kao F J , Cheng P C , Cheng P C
Published: July 2020

Multi-photon fluorescence microscopy has been cited for its advantage in increased depth penetration due to low linear absorption coefficient of biological specimen in the near infrared (NIR) range. Using a pulsed laser, it is possible to efficiently excite two-photon fluorescence with a high peak power while keeping the average power low to avoid thermal and photochemical damages to the specimen. Currently, mode-locked Ti-sapphire and Cr-Forsterite lasers that generate sub-picosecond pulses are used as the light source for multi-photon fluorescence microscopy. Because of the need of high peak power for efficiently exciting two-photon fluorescence, the relationship between cell damage and peak power has become an interesting and much debated topic in the application of multi-photon fluorescence microscopy. It is conceivable that at high illumination intensity, non-linear photochemical processes may have impacts on cell physiology and viability in ways much different from low illumination in the linear domain.
Multi-photon Fluorescence Micro-spectroscopy of Plant Tissues
Authors: Kao F J , Lin B L , Cheng P C
Published: July 2020

Considering its non-linear nature, two-photon excitation may generate very different spectral response in samples when compared with single photon excitation. It is thus necessary to measure the two-photon spectra of samples, so that the two-photon fluorescence microscopic images can be properly interpreted. Fluorescence spectra obtained from bulk samples may not provide useful information for microscopy. For instance, due to the relatively small contribution to the total fluorescence intensity, a small number of fluorescent particles in a generally fluorescing specimen may escape detection when the spectrum of the specimen as a whole is obtained. Under two-photon excitation, the background noise can be greatly reduced due to the naturally limited excitation volume of focused laser beam. In addition, signals resulted from second harmonic generation (SHG) may be mixed with low level broad-band background autofluorescence which is commonly found in biological specimen. Therefore, measuring fluorescence spectrum from a micro-focused volume is essential for the proper interpretation of multi-photon fluorescence images.
Use of Confocal Imaging for Arthropod Morphological Studies
Authors: Klaus Angela V , Kulasekera Varuni L , Platnick Norman
Published: July 2020

Morphological studies in spider and insect groups (Phylum Arthropoda) have historically relied upon traditional imaging techniques such as light microscopy (LM) and scanning electron microscopy (SEM). It has often been difficult, however, to examine some structural details of certain specimens due to limitations of the techniques. Light microscopy does not always provide adequate depth of focus for visualizing the true three-dimensional structure of a specimen, and out-of-focus light in the image can obscure detail. SEM is not applicable if the specimen is too delicate to undergo critical point drying. Additionally, SEM is a surface technique and does not provide any information about internal structure.

If a specimen is transparent to light, information about the morphology of internal structures, and connections between structures, can easily be obtained using confocal microscopy without the problems associated with traditional LM. In this study, we used confocal laser scanning microscopy (CLSM) to study the morphology of chitinous arthropod structures by taking advantage of their autofluorescent properties.
High Resolution Optical Microscopy Will Play a Major Role in Functional Assessments and the Prevention of Disease
Authors: Bradford, Chairman Robert W , Oversight Curriculum
Published: July 2020

The typical aging processes can be characterized by a gradual alteration and essential breakdown of the functional systems of the body. Numerous factors play important roles in the alterations of these pathways from biochemical individuality and genetic predisposition to environmental insults and deficiency states.1 Clinical research, as but one example, has clearly documented the role of free radicals (ROS) or oxidative injury in disease and aging affecting the body's basic cellular structures.

The objective of functional or health assessments is to be able to detect in vivo stresses and imbalances in the biological systems, while the patient is asymptomatic, so that early therapeutic intervention can resolve the problems prior to disease onset or accelerated aging. The ability to assess risk factors and treat the sub-clinical metabolic toxicities, deficiency states, hormonal imbalances, oxidative injury (ROS), immunodeficiencies, enzyme down regulations, antioxidant status, metal toxicities, cardiovascular stresses, organ reserves/stresses and detox systems in a low-complexity, cost-effective office procedure is true preventive medicine.
Laser Capture Microscopy as an Aid to Ultrastructural Analysis
Authors: Grant K W , Anderson N J , Hammarback J A , Sweatt A , Dawson B , Moore P , Jerome W G
Published: July 2020

Laser capture microdissection (LCM) is a technique that provides homogenous cell populations for molecular and light microscopic analysis. During viewing by a standard wide-field microscope, a specific cell is selected. Heat from a near-infrared laser melts an ethylene vinyl acetate (EVA) transparent film which bonds to the individual selected cell. Several thousand cells can be selected and captured using this method. A homogeneous subpopulation of cells may be collected, one at a time, by histologic characteristics and/or histochemical staining from frozen sections, deparaffinized tissue, cell cultures or a blood smear.

Previously, this technique has primarily been used to capture cells for DNA or RNA analysis. This study was undertaken to investigate the possibility of capturing a subpopulation of cultured cells in order to study their ultrastructure with the transmission electron microscope (TEM). We report here that cultured cells can be processed, captured and embedded for electron microscopy, in such a manner as to maintain ultrastructure.
Ultrastructural and Histological Analysis of the Bone-Implant Interface
Authors: Steflik DE , Corpe RS , Young TR , Parr GR , Sisk AL
Published: July 2020

The bone interface to implanted biomaterials (both orthopaedic and dental implants) is the critical component for initial fixation of these uncemented biomedical devices. The mechanism of osteogenesis at the biomaterial surface after surgical placement is critical to understand to enhance osseointegration, and thereby implant success. The purpose of this paper is to report comprehensive and correlative electron and light microscopic observations from a five-year study involving the bone interface to 120 implants placed into 30 adult animals.

As a model system to evaluate bone and associated tissue interfaces to implanted biomaterials, 120 endosteal dental implants were placed into the mandibles of 30 adult mongrel dogs. Premolars were extracted and the sites were allowed to heal for 2 months prior to implantation. Surgery employed low speed drilling, copious internal and external irrigation and followed manufacturer recommendations for these commercially available implants.