bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural modifications of the pineal gland of aged rats: Role of calcium
Authors: Humbert W. , Pévet P. 
Published: June 2020

The pineal gland, an important component of the neuroendocrine axis [review in Reiter] is known to play an important role in chronobiology and transduction of certain external stimuli. The purpose of the present investigation is to examine the pineal gland of young and aged rats and to determine structural and elemental alterations related to age.28 months-old male Wistar rats and young adult males (2-3 months old) were used. Pineal glands were quickly removed from the brain after decapitation and fixed with 3% gl utaraldehyde in 0.1 M Na cacodylate buffer (1h) and postfixed in 1% OsO4 buffered with 0.1 M Na cacodylate. For ultrastructural localization of calcium the potassium pyroantimonate method was used following the method of Eisenmann et al. Calcium was analyzed using a CAMEBAX mi croanalyser with the TEM mode and fitted with WDS spectrometers.
Intracellular motility and actin polymerization induced by Listeria monocytogenes in infected cells
Authors: Sanger J.M. , Mittal B. , Southwick F.S. , Sanger J.W. 
Published: June 2020

The bacterium, Listeria monocytogenes can be phagocytosed by macrophages and epithelial cells. Within an hour, the bacteria can assemble host cell actin into bundles or tails and move inside the living cells at rates up to 1.4μm/sec. In seeking to determine the mechanisms responsible for the intracellular movements of this bacterium, our working hypothesis is that actin polymerization is not only necessary for the movement but the polymerization reaction itself provides the force to move the bacteria in the host cytoplasm.PtK2 cells, an epithelial cell line, were infected with Listeria and were then microinjected with fluorescently labeled cytoskeletal proteins (actin, alpha-actinin, filamin, tropomyosin, skeletal muscle light chains) and a control fluorescent protein (bovine serum albumin, BSA). Some infected cells were sequentially injected first with fluorescently labeled cytoskeletal proteins and then with proteins that bind monomelic actin (Vitamin-D binding protein; DNAase I; profilin).
Localization of acid phosphatases in root cap of rice plant
Authors: Chen Y. R. , Huang Y. F. , Chen W. S. 
Published: June 2020

Acid phosphatases are widely distributed in different tisssues of various plants. Studies on subcellular localization of acid phosphatases show they might be present in cell wall, plasma lemma, mitochondria, plastid, vacuole and nucleus. However, their localization in rice cell varies with developmental stages of cells and plant tissues. In present study, acid phosphatases occurring in root cap are examined.Sliced root tips of ten-day-old rice(Oryza sativa)seedlings were fixed in 0.1M cacodylate buffer containing 2.5% glutaraldehyde for 2h, washed overnight in same buffer solution, incubated in Gomori's solution at 37° C for 90min, post-fixed in OsO4, dehydrated in ethanol series and finally embeded in Spurr's resin. Sections were doubly stained with uranyl acetate and lead citrate, and observed under Hitachi H-600 at 75 KV.
New views inside cells with a digital imaging microscope
Authors: Fay F. S. , Fogarty Kevin , Tuft Richard , Carrington Walter 
Published: June 2020

Many current questions in cell biology revolve around questions regarding how changes in cell function are caused by changes in their molecular composition. Given that cells are highly organized structures often carrying out diverse functions in different compartments, it follows that changes in specific cell functions must involve highly localized changes in molecular composition.We have been involved in the development of the digital imaging microscope as a tool to investigate the distribution of molecules inside single living cells. The system measures fluorescence of probes that are highly fluorescent and specific for a molecule or ion of interest and utilizes a wide-field rather than a confocal microscope to produce an image of fluorescence in a single cell. The image is captured by a high quantum efficiency, low noise cooled CCD, thereby providing ultrahigh efficiency in the acquisition of fluorescent images. By utilizing very powerful light sources, the system is capable of generating an image with good signal-to-noise ratio in a millisecond or less, thereby allowing one to follow extremely rapid changes in molecular or ion distribution in single cells.
Induction of chromatoid bodies in trophozoites of Entamoeba invadens growing in log phase at high CO2 tension
Authors: Ramirez-Bon E. , Villarreal-Treviño L. , Morales-Vallarta M. 
Published: June 2020

Entamoeba invadens is an ameba that parasites reptiles; it is very similar in morphology and physiology to Entamoeba histolytica. Due to this, it is used as an - experimental model for amebiasis research, specially in the differentiation process, since E. invadens can be induced to “in vitro” encystment, which is not possible — with E. histolytica.Chromatoid bodies, are arrays of helical structures formed by the aggregation of ribosomes, that are found only in cystic forms of E. invadens, in trophozoites cultured in slow growing conditions, or in the presence of protein synthesis inhibitors. This paper reports the formation of chromatoid bodies in trophozoites of E. invadens in active growing phase and high CO2 tension.
Immunogold labeling of Pneumocystis carinii for Electron microscopy
Authors: Goheen Michael P. , Bartlett Marilyn S. , Smith James W. 
Published: June 2020

Studies of the biology of Pneumocystis carinii (PC) are of increasing importance because this extracellular pathogen is a frequent source of severe pneumonia in patients with acquired immunodeficiency syndrome (AIDS) and is a leading cause of mortality in these patients. Immunoelectron microscopic localization of antigenic sites on the surface of PC would improve the understanding of these sites and their role in pathenogenisis of the disease and response to chemotherapy. The purpose of this study was to develop a methodology for visualizing immunoreactive sites on PC with transmission electron microscopy (TEM) using immunogold labeled probes.Trophozoites of PC were added to spinner flask cultures and allowed to grow for 7 days, then aliquots of tissue culture fluid were centrifuged at 12,000 RPM for 30 sec. Pellets of organisims were fixed in either 1% glutaraldehyde, 0.1% glutaraldehyde-4% paraformaldehyde, or 4% paraformaldehyde for 4h. All fixatives were buffered with 0.1M Na cacodylate and the pH adjusted to 7.1. After fixation the pellets were rinsed in 0.1M Na cacodylate (3X), dehydrated with ethanol, and immersed in a 1:1 mixture of 95% ethanol and LR White resin.
Artifact-free electron microscopic immunocytochemistry on rat brain tissue
Authors: Burmeister Veronika , Ludvig N. , Jobe P.C. 
Published: June 2020

Electron microscopic immunocytochemistry provides an important tool to determine the ultrastructural distribution of various molecules in both normal and pathologic tissues. However, the specific immunostaining may be obscured by artifactual immunoreaction product, misleading the investigator. Previous observations show that shortening the incubation period with the primary antibody from the generally used 12-24 hours to 1 hour substantially reduces the artifactual immunostaining. We now extend this finding by the demonstration of artifact-free ultrastructural localization of the Ca2/calmodulindependent cyclic nucleotide phosphodiesterase (CaM-dependent PDE) immunoreactivity in brain.Anesthetized rats were perfused transcardially with phosphate-buffered saline followed by a fixative containing paraformaldehyde (4%) and glutaraldehyde (0.25%) in PBS. The brains were removed, and 40μm sections were cut with a vibratome. The sections were processed for immunocytochemistry as described by Ludvig et al. Both non-immune rabbit serum and specific CaM-dependent PDE antibodies were used. In both experiments incubations were at one hour and overnight. The immunostained sections were processed for electron microscopic examination.
Localization of actin in the salivary glands of the American dog tick,Dermacentor variabilis
Authors: Lamoreaux William , Sankhon Naby , Coons Lewis B. 
Published: June 2020

The salivary glands of ixodid ticks are the primary organs of osmoregulation and the source of pathogen transfer from tick to host. Excess fluid is extracted from the blood meal, moved across the gut wall and into the salivary glands, where it is returned to the host. Previously it has been shownin vivoandin vitrothat the type III acinus alternately swells as it fills with fluid and then contracts as the acinus empties, and that cytochalasin D prevents contraction of the type III acini.In this investigation, the rhodamine-phalloidin technique was used to localize actin filaments in the salivary glands of fed mated female ticks. Two microfilament inhibitors were used as controls. Samples were also taken for electron microscopy and dot blot analysis.
Image formation in the scanning electron microscope
Authors: Wells Oliver C. 
Published: June 2020

Image formation in the scanning electron microscope (SEM) was discussed in theory by von Ardenne. It was reduced to practice by von Ardenne, Knoll, McMullan, Smith and Oatley and Smith. The basic ideas are as follows. An electron beam (EB) of diameter dEBis scanned over a solid specimen. This penetrates for a distance dPENbelow the surface. A signal is collected and modulates the brightness of a cathode ray tube scanned in sympathy with the EB. While the resolution is always limited by dEB, it is not always limited by dPEN.Secondary electron (SE) imaging. von Ardenne distinguished between the secondary electrons (SE) with an energy lower than 50 eV and the backscattered electrons (BSE) having energies between 50 eV and the primary energy E0. He proposed that SE that escape at the point of entry of the EB (now called SE-I) should provide a high resolution component to the SE image, while SE excited at the exit point (now called SE-II) escape from a larger area and so give rise to an image with a poorer resolution. (Also see Peters.6)
Development of a digital SEM
Authors: Yamada A. , Shibano A. , Harasawa K. , Kobayashi T. , Fukuda H. , Saito M. , Nielsen C. H. , Nakagawa S. 
Published: June 2020

A newly developed digital scanning electron microscope, the JSM-6300, has the following features: Equipped with a narrower conical objective lens (OL), it allows high resolution images to be obtained easily at a short working distance (WD) and a large specimen tilt angle. In addition, it is provided with automatic functions and digital image processing functions for ease of operation.Conical C-F lens: The newly developed conical C-F objective lens, having low aberration characteristics over a wide WD range, allows a large-diameter (3-inch) specimen to be tilted up to 60° at short WD, and provides images with low magnifications starting at 10*. On the bottom of the lens, a p n junction type detector is provided to detect backscattered electrons (BE) from the specimen. As the narrower conical 0L increases the secondary electron (SE) detector's field intensity on the specimen surface, high SE image quality is obtained.
Vibrations of turbo-molecular vacuum pumps with high stable magnetic bearings operating within electronic microscope systems
Authors: Thomas C. A. , Reimer K. P. 
Published: June 2020

In order to operate Electronic Microscopes vibration free, it is necessary to assemble the apparatus on a vibration free isolated desk. Similarly, strict requirements, regarding vibrations, are demanded from the attached vacuum pump which provides vacuum for the system. The rotor and rotating shaft of Turbo Molecular Pumps with mechanical bearings are connected to the pump housing by means of ball bearings. The inertia and vibration component resulting from the ball bearing dynamic effects produce the vibration results as indicated in Fig. 1.In order to design a Turbo Molecular Pump with minimum vibration effects it was necessary to provide the pump with a magnetic bearing system containing 4 passive and 1 active controlled axis. This magnetic bearing system is less sensitive to vibration and simpler in assembly than other existing more complicated 5-axis active controlled versions. However it is more complication than the mechanical bearing type. The magnet bearing is provided with a touch-down bearing. Larger pump movements due to high or low frequency stimulation recieved via the microscope desk could result in forcing the shaft out of its magnet-bearing-centre position, the touch-down bearing now re-centres the shaft allowing immediate magnetic bearing centre recovery.
Imaging molecules and metals on metal surfaces by scanning tunneling microscopy
Authors: Chiang S. , Chambliss D. D. , Hallmark V. M. , Wilson R. J. , Brown J. K. , Wöll Ch. 
Published: June 2020

Using an ultrahigh vacuum scanning tunneling microscope (STM), we have imaged naphthalene molecules adsorbed on Pt(111) and submonolayer metal coverages of Ni, Fe, Ag, and Au on Au(111). The STM is able to observe atomic scale features on both types of systems, giving information on the ordering and binding sites of atoms and molecules on the surface.High resolution STM images of naphthalene on Pt(111) show the molecules as bi-lobed features with three discrete molecular orientations on the surface, 120° apart, as shown for the ordered layer in Fig. 1. The absolute orientation of the long axis of the molecules is observed to be parallel to the near-neighbor directions of the Pt(111) lattice. The sketch of the observed features, shown in Fig. 2, with the molecules overlayed arbitrarily onto on-top sites of a Pt(111) lattice, demonstrates that the molecules are located on 3x3 lattice sites, with separation of 4 lattice constants between domains. Although the (6x3) LEED pattern reported previously was reproduced, the proposed unit cell is seldom observed in the STM images.
Scanning tunneling microscopy ofE. coliRNA polymerase deposited onto an Au substrate by an electrochemical process
Authors: Keller Rebecca W. , Bustamante Carlos , Bear David 
Published: June 2020

Under ideal conditions, the Scanning Tunneling Microscope (STM) can create atomic resolution images of different kinds of samples. The STM can also be operated in a variety of non-vacuum environments. Because of its potentially high resolution and flexibility of operation, it is now being applied to image biological systems. Several groups have communicated the imaging of double and single stranded DNA.However, reproducibility is still the main problem with most STM results on biological samples. One source of irreproducibility is unreliable sample preparation techniques. Traditional deposition methods used in electron microscopy, such as glow discharge and spreading techniques, do not appear to work with STM. It seems that these techniques do not fix the biological sample strongly enough to the substrate surface. There is now evidence that there are strong forces between the STM tip and the sample and, unless the sample is strongly bound to the surface, it can be swept aside by the tip.
An improved design for an Scanning Tunnelling Microscope (STM) for use in a Transmission Electron Microscope (TEM)
Authors: Lo W.K. , Spence J.C.H. 
Published: June 2020

An improved design for a combination Scanning Tunnelling Microscope/TEM specimen holder is presented. It is based on earlier versions which have been used to test the usefulness of such a device. As with the earlier versions, this holder is meant to replace the standard double-tilt specimen holder of an unmodified Philips 400T TEM. It allows the sample to be imaged simultaneously by both the STM and the TEM when the TEM is operated in the reflection mode (see figure 1).The resolution of a STM is determined by its tip radii as well as its stability. This places strict limitations on the mechanical stability of the tip with respect to the sample. In this STM the piezoelectric tube scanner is rigidly mounted inside the endcap of the STM holder. The tip coarse approach to the sample (z-direction) is provided by an Inchworm which is located outside the TEM vacuum.
Nanometer-sized tungsten tips for STM and AFM
Authors: Fotino Mircea 
Published: June 2020

An essential requirement in the pursuit of atomic resolution by scanning tunneling microscopy (STM) or atomic force microscopy (AFM) is the use of a tip with an apex of dimensions comparable to or preferably smaller than those of the specimen to be identified. Although atomic resolution of mostly planar specimens has been obtained even with atomically blunt tips, the above requirement appears indispensable for determining 3D surface structures extending equally in all three dimensions.Tips most commonly used so far in STM or AFM applications are made by grinding or by etching a thin and rigid Pt/Ir or W wire. Mechanical grinding occasionally leaves protruding spikes typically several tens of nm in radius that can play the role of scanning stilus even though neither adequately oriented nor particularly sharp and symmetric.
Research thrusts employing intermediate-voltage analytical microscopy
Authors: Garratt-Reed Anthony J. 
Published: June 2020

Although commercial analytical electron microscopes equipped with field-emission electron guns operating at 100kV have been in routine use in laboratories in many countries for over 15 years, and while there has been a general appreciation that for certain studies (e.g. catalyst research) such instruments are invaluable tools, there has been little consensus on what results can be expected from such microscopes when used for study of more generalized samples, and in particular their ability to resolve chemical detail in the thin-foil samples typical of much materials research.200kV field-emission microscopes have already been delivered to customers by Hitachi, and at the time of writing, the first 300kV field-emission STEM is in the final stages of factory test, having already demonstrated an image resolution of 0.3nm point-to-point and excellent x-ray characteristics, and is expected to be delivered to the authors1 laboratory within a few weeks.
High-resolution electron holography
Authors: Lichte Hannes 
Published: June 2020

The performance of an electron microscope usually is described in Fourier space by means of the wave transfer function WTF(R) = B(R) exp(iχ(R)) with the pupil function B(R) and the wave aberration χ(R). R means the spatial frequency, rotational symmetry is assumed.The exp(iχ(R)) term describes the coherent transfer of the object wave a(r)exp(iφ(r)) into the image wave A(r)exp(iФ(r)). For weak specimen (a≈1 and φ<<27π) this transfer can be sketched by means of fig. 1 which shows that a mixing occurs between the amplitudes and phases according to the respective transfer functions cosχ and sinχ. Usually, it is desirable to direct by an appropriate wave aberration x the phase of the object wave - containing the most interesting information about the object structure - into the image intensity A2. This is achieved best at Scherzer focus, however, only a comparably narrow band of spatial frequencies is evenly transferred. Lower spatial frequencies (“Large area phase contrast“) are not found in the image.
Quantum noise characteristics in TEM images measured by means of imaging plate
Authors: Oikawa T. , Mori N. , Hosokawa F. , Kawasaki M. 
Published: June 2020

In the observation of the beam sensitive specimens, it is required to minimize the electron dose. At a very low electron dose, however, the electrons themselves become quantum noise, thus lowering the image quality regardlessly of the performance of the detectors. In the present study, the relationship of quantum noise with the image signal included in TEM images has been measured by means of the Imaging Plate (IP), which is a high sensitivity detector.The instrument used was the TEM-IP system, a PIXsysTEM based on the JEM-2000FXII.Phase contrast images of the amorphous film were taken at a very low dose where quantum noise is dominant. The images were taken using an objective lens with a spherical aberration constant of 2.3 mm and an accelerating voltage of 200 kV. The spatial frequencies included in the images were estimated by Fourier transformation, which was carried out on the IP-processor of the PIXsysTEM, by using the original data from the IP. In this experiment, it was already ascertained that system noise (noise due to the instrument) is negligible.
On the iterative restoration of exit plane wave function from defocus series in HREM
Authors: Gribelyuk M.A. , Hutchison J.L. 
Published: June 2020

The validity domain of a Multiple Image MAximum Posteriori (MIMAP) approach has been estimated on UMo5O16 complex oxide structure (Fig.1). Model defocus series (both noise-free and with an additive random noise) have been prepared by multislice method with no objective aperture imposed. Defocus values Δfn=((8n+3)Csλ/2)05 (n=0,...,4) corresponded to plateaus of JEOL-4000EX microscope transfer function operated under U=400kV. The following problems are considered:Self-consistency. Apart from a wave function MIMAP aims at refinement of translational misalignment, difference in defocus values within series and a “fog” level c0. The latter represents an additive constant to image intensity arising by image recording and manipulation. We assumed that defocus values were known exactly and images were perfectly aligned. If one sets c01 to its exact value c0=0 and starts restoration from noise-free defocus series of a t=12 thin crystal the procedure will diverge (Fig.2).
HREM observation of interface between precipitates and martensite of reversible shape memory alloy Ni-Ti
Authors: Song Zhiyi , Hashimoto Hatsujiro , Sukedai Eiichi 
Published: June 2020

Since the reversible shape memory (RSM) alloys were found in 1960, a number of investigations and applications have been carried out and the mechanism have been discussed extensively. Ni-Ti is one of the typical RSM alloys. Many researches were concentrated on martensite structure and the relationship between martensite and austenite. However, the interface structures between martensite and precipitates have been rarely studied. In the present paper, the interface structures between precipitates ( NiTi2 and Ni3Ti) and martensite were investigated in atomic scale by using nigh resolution electron microscopy.49.5at%Ni-50.5at%Ti alloy whose martensitic transformation temperature is 75°C was annealed at 900°C for 2 hours to allow the components to become uniformly distributed, then quenched into water at room temperature. The specimens for electron microscopy observation were prepared by spark cutting and electropolishing. A JEM-2000EX and JEM-4000EX operated at 200kv and 400kv, respectively were used in the present observations.
Microanalysis with a 200keV FEG TEM
Authors: Joy David C 
Published: June 2020

Introduction The Hitachi HF-2000 is a 200keV cold field emitter TEM, designed to offer both high resolution imaging performance and a nanometer probe-forming mode for microanalytical operation. The purpose of this paper is to report some initial microanalytical results obtained from the HF-2000 installed at the University of Tennessee.General Electron-Optical Parameters The cold field emission gun, which runs at about 5x10-9pA pressure, uses an electrostatic lens configuration and a six stage accelerator. The entire electron gun system is under the control of a dedicated microprocessor which permits all of the operational parameters of the gun to be set, monitored, and adjusted through a keyboard and display. The tip emission current can be adjusted up to 40μA, and the gun voltage ratio (that is the ratio between the voltage on the second anode and the tip extraction voltage) can be varied from 4.5 to 7.5, permitting a significant degree of flexibility in optimizing the optics of the emitter.