bluuebunny/crossref_metadata_2025 huggingface dataset:
Cryo-electron and optical microscopy study of lipid-encapsulated microtubules
Authors: Bisher M. E. , Fygensont D. K. , Booy F. , Libchabert A. , Treacy M. M. J.
Published: June 2020

The dimeric protein tubulin is found in every eukaryotic cell. In the presence of GTP and Mg++ cations, tubulin polymerizes into long hollow cylinders known as microtubules, that are 24 nm in diameter and can grow as long as 10-100 μm in length. Microtubules play an important role in living cells: they act as guides for internal molecular transport (most notably the separation of genetic material during anaphase in cell division), they are a major component of the cytoskeleton, and are important structural constituents of cilia and flagellae. Locomotion, morphogenesis and reproduction, are fundamental cellular processes that rely on the polymerization of microtubules and on their ability to re-organize - a feature termed dynamic instability.

Tubulin, purified from fresh cow brain, exhibits this dynamic instability in the laboratory in the absence of microtubule-associated protein. Length fluctuations can be observed by differential interference contrast (DIC) optical microscopy. The instability persists when tubulin is encapsulated in lipid vesicles (liposomes), formed by adding the phospholipids DOPC and DOPS, and applying the freeze-thaw technique to the mixture. Fig. 1 shows a DIC optical micrograph of a ˜5 (im lipid vesicle that is distorted, or impaled, by a 12 μm rod which is presumably a microtubule, or a bundle of microtubules. Frequently, such microtubules are observed to buckle because of reaction forces from the membrane.
New tools for Atomic Force Microscopy
Authors: Prater C. B.
Published: June 2020

The Atomic Force Microscope (AFM) has been widely used in the physics, chemistry, and materials science communities, and is becoming more common in life sciences research. To better serve the biological community, new instruments have been developed recently that combine AFM and various forms of optical microscopy including EPI-fluorescence, DIC, and confocal microscopy. In addition, new techniques like fluid Tapping Mode™ have been developed to allow gentle, non-destructive imaging of biological samples, including live specimens in physiological conditions. Other new techniques can provide information about sample elasticity or molecular adhesion along with nanometerscale topography measurements.

Until recently, most AFMs scanned the sample under a stationary probe using a small piezoelectric scanner. This arrangement placed serious limits on the size and type of sample that could be used as a sample substrate. Now instruments have been developed that scan the AFM probe over a fixed sample that then allows imaging of larger, more convenient sample substrates, including cover slips, slides, and even petri dishes.
Mussel adhesive protein as a novel substrate for Atomic Force Microscopy
Authors: D'Costa Neill P. , Hoh Jan H.
Published: June 2020

Atomic Force Microscopy (AFM) requires immobilization of samples to a suitable substrate. Immobilized samples must withstand forces, particularly lateral forces, exerted by the tip during imaging. Air-drying is the simplest way of immobilizing molecules onto a substrate. However, this often compromises the integrity of structural features because of forces at the air-liquid interface. In solution the most common method is simple adsorption. While very convenient, this method works only for a limited number of samples. To overcome this problem procedures involving covalent chemical cross-linking have been developed. We have developed an alternative AFM substrate based on the mussel adhesive protein (MAP) from Mytilus edulis. This substrate is simple to prepare and can immobilize a wide range of samples, including gold particles, silica spheres, proteins, and nucleic acids.

MAP is a polyphenols marine adhesive by which the mussel attaches itself to different surfaces. Studies of purified MAP indicate that it possesses a unique chemistry.
The nuclear envelope and nuclear pore complex as seen by high-resolution field emission SEM and high voltage TEM
Authors: Ris Hans
Published: June 2020

The nuclear envelope (NE) consists of an inner membrane and an outer membrane continuous with the endoplasmic reticulum. The membranes are fused at the nuclear pores, which connect cytoplasm with nuclear space. Located in these pores is the nuclear pore complex (NPC) which controls the transport of macromolecules across the NE. Attached to the inner surface of the NE is a network of 10 nm lamin filaments, the nuclear lamina. Recent studies using high voltage TEM and field emission “in lens” SEM have greatly advanced our knowledge of NPC structure, particularly the components facing the cytoplasm and nuclear space. The cytoplasmic face consists of a 120 nm ring carrying 8 twisted filaments condensed into 20×40 nm cylinders. On the nuclear side is another 120 nm ring, from which 8 filaments, 5 nm thick and 50 nm long, extend into the nuclear space. Each filament ends in a 10 nm bead. The 8 beads are joined into a 50 nm ring, forming the top of a fishtrap-like structure. Usually this ring is obscured by distorted pore connecting fibers.
Critical issues in the application of image cytometry to the early detection of lung and cervical cancer
Authors: Garner D.M , MacAulay C.E. , Palcic B.
Published: June 2020

Screening for cervical cancer (“Pap screening”) is probably the largest single application of absorbance microscopy in medicine, with 50-60 million samples screened per year in the United States alone. Pap screening also represents one of the great success stories in cancer management having reduced the morbidity and mortality due to cancer of the uterine cervix by 50 - 80% in regions where mass Pap screening is carried out. Despite this success, the subjective manual examination of stained cellular specimens with a microscope in current Pap screening practice results in significant over treatment. We estimate that for every 30 women currently treated for early cervical cancer, only one would actually develop invasive cancer in the absence of the Pap screening programme.

One key question then is: “Could image cytometry, the objective measurement of cells, improve the current Pap screening programmes by reducing the number of unnecessary medical interventions, without subjecting the patients to undo risk?”
Dynamics of dendrite development visualized by time-lapse confocal imaging in brain slices
Authors: Dailey M.E. , Smith S.J.
Published: June 2020

In the mammalian CNS, dendritic neuronal branches typically are studded with numerous short (<3μm), lateral protrusions called “spines”. Such spines are the primary sites of excitatory synaptic input, and changes in spine morphology are thought to play important roles in plasticity of synaptic function in both the developing and adult animal. However, dynamic changes in spine number and structure are not easily determined by electron microscopy, and the small size of spines has made them difficult to study by conventional light microscopy. Recent advances in vital fluorescent staining and high resolution confocal imaging in tissue slices now afford the possibility of assessing changes in morphology of individual spines on single dendrite branches over time.

To investigate the dynamics and plasticity of dendritic structure during development, vital fluorescent staining and time-lapse confocal imaging methods were applied to preparations of live brain slices from developing rat. Tissue slices were prepared from hippocampus of neonatal rat (postnatal day 2-7) and cultured for variable periods of time (hours to weeks).
Development of optimal protocols for antigen retrieval immunohistochemistry based of the effects variation in temperature and pH: use of a ‘test battery’
Authors: Shi S.-R. , Cote R.J. , Young L. , Yang C. , Chen C. , Grossfeld G.D. , Ginsberg D.A. , Hall F.L. , Taylor C.R.
Published: June 2020

Following development of the microwave antigen retrieval (AR) technique in 1991 for enhancement of immunohistochemical (IHC) staining, there have been numerous articles published worldwide describing the use of AR-IHC on archival tissue sections. The AR technique provides a method for retrieval of formalin-masked antigens which otherwise yield negative or very weakly positive IHC staining on archival paraffin sections. AR appears to be superior to other unmasking procedures, and serves to reduce detection thresholds of IHC for a wide range of antigen antibody systems. One important result is that AR increases the accuracy of diagnosis when using IHC for pathology. However, certain critical issues remain concerning the optimal protocol, the choice of AR solution, pH and the precise heating conditions. These aspects of AR-IHC require further study in order to improve standardization of AR-IHC, as emphasized by Taylor. Based on our recent study of AR-IHC under the influence of pH, we designed a new study specifically to examine the effect of different microwave heating conditions.
Comparison of 13Å helical and 7Å crystallographic projection maps of frozen, hydrated acrosomal bundle from limulus sperm
Authors: Schmid Michael F. , Jakana Joanita , Matsudaira Paul , Chiu Wah
Published: June 2020

Actin associates with crosslinking proteins to form bundles and networks. These assemblies can provide a scaffold to anchor organelles, a support for the cell membrane or can attach the cell to the extracellular matrix or to other cells. Each crosslinker must have at least two actin binding sites, one for each actin filament. Scruin, in the Limulus acrosomal bundle, shows no homology with other actin cross-linking proteins. However, it has two homologous domains also found in the sequence encoded by kelch, a gene in Drosophila that is important in nutrient transport into the oocyte, and in MIPP, a mouse placental protein.

We have determined a 13Å helical 3-dimensional structure of the actin-scruin complex, which is the basic repeat unit of the acrosomal bundle in Limulus sperm and have fitted the F-actin filament of Holmes. Each scruin binds to two adjacent actin molecules along a single F-actin filament helix. In the present investigation, we used our high resolution (7Å) spot scan electron images of ice-embedded acrosomal bundles for further analysis of the actin atomic map and scruin-scruin contacts. Spot-scan images were obtained from the frozen, hydrated acrosomal bundles in a 400 kV electron cryomicroscope.
Mapping traction forces generated by motile cells
Authors: Oliver Tim , Pletjuushkina Olga J. , Vasiliev Juri M. , Dembo Micah , Jacobson Ken
Published: June 2020

In a continuing effort to understand how cell-generated traction forces are utilised for locomotion, we have applied our modified silicone rubber traction force assay to rapidly locomoting fish epidermal keratocytes executing turns and shape changes, and negotiating obstacles. The resulting maps show that these cells can redistribute tractions from the “steady-state” pattern (previously observed during unobstructed, gliding locomotion), into a variety of transient patterns, with lifetimes of less than 1 minute (Figs. 1-4). The map for a “steady state” locomoting keratocyte shows a maximum traction force density of ~5x10-5 dynes/μm (data not shown). This value was derived from cell-free experiments in which elastic films were manipulated with a pair of micronneedles. Such experiments, in which all forces were known, showed that both the magnitude and direction of traction forces applied to the film could be closely predicted, and that the Young’s modulus of elasticity for the silicone substratum could be calculated. The consequences for understanding the underlying molecular basis for shape change and cell motility from this type of analysis will be discussed.
Glucuronyl 3-sulfate occurs exclusively on distal unmyelinated terminals of selected sensory neurons in the peripheral nervous system
Authors: Spicer S.S. , Schulte B.A.
Published: June 2020

Generation of monoclonal antibodies (MAbs) against tissue antigens has yielded several (VC1.1, HNK- 1, L2, 4F4 and anti-leu 7) which recognize the unique sugar epitope, glucuronyl 3-sulfate (Glc A3- SO4). In the central nervous system, these MAbs have demonstrated Glc A3-SO4at the surface of neurons in the cerebral cortex, the cerebellum, the retina and other widespread regions of the brain.

Here we describe the distribution of Glc A3-SO4in the peripheral nervous system as determined by immunostaining with a MAb (VC 1.1) developed against antigen in the cat visual cortex. Outside the central nervous system, immunoreactivity was observed only in peripheral terminals of selected sensory nerves conducting transduction signals for touch, hearing, balance and taste. On the glassy membrane of the sinus hair in murine nasal skin, just deep to the ringwurt, VC 1.1 delineated an intensely stained, plaque-like area (Fig. 1). This previously unrecognized structure of the nasal vibrissae presumably serves as a tactile end organ and to our knowledge is not demonstrable by means other than its selective immunopositivity with VC1.1 and its appearance as a densely fibrillar area in H&E stained sections.
DNA nick end labeling: a reliable marker for apoptosis?
Authors: Bushnell Anne F. , Webster Sarah , Perlmutter Lynn S.
Published: June 2020

Apoptosis, or programmed cell death, is an important mechanism in development and in diverse disease states. The morphological characteristics of apoptosis were first identified using the electron microscope. Since then, DNA laddering on agarose gels was found to correlate well with apoptotic cell death in cultured cells of dissimilar origins. Recently numerous DNA nick end labeling methods have been developed in an attempt to visualize, at the light microscopic level, the apoptotic cells responsible for DNA laddering.

The present studies were designed to compare various tissue processing techniques and staining methods to assess the occurrence of apoptosis in post mortem tissue from Alzheimer's diseased (AD) and control human brains by DNA nick end labeling methods. Three tissue preparation methods and two commercial DNA nick end labeling kits were evaluated: the Apoptag kit from Oncor and the Biotin-21 dUTP 3' end labeling kit from Clontech. The detection methods of the two kits differed in that the Oncor kit used digoxigenin dUTP and anti-digoxigenin-peroxidase and the Clontech used biotinylated dUTP and avidinperoxidase. Both used 3-3' diaminobenzidine (DAB) for final color development.
Cytoplasmic inclusion bodies in familial dilated cardiomyopathy
Authors: Gunning W.T. , Gohara A.F. , Walsh T.E. , Calomeni E.P.
Published: June 2020

A thirty-six year old male with severe congestive heart failure was given a cardiac transplant. The findings of the evaluation of his native heart is the basis for this presentation. Our findings included the identification of unusual cytoplasmic inclusion bodies found throughout the heart. These inclusions, found most often in a perinuclear location, were eosinophilic and crystalloid at the light microscopic level (Figure 1.). Special histologic stains were not supportive of a diagnosis of nemaline rod disease as a trichrome stain failed to differentiate inclusions from surrounding cytoplasm, yet could be accomplished with PAS staining (Figure 2.) . Furthermore, the ultrastructural morphology of the inclusions did not show any similarity to z-band material, the electron microscopic characteristic of inclusion bodies in nemaline rod myopathy. The shape of these bodies was usually rectangular or elliptical (Figure 3.) and size was found to be quite variable, some measured in excess of 15μ X 4μ. Other characteristics included an amorphous appearance with occasional electron densities within the inclusions (Figure 3), an apparent single limiting membrane (Figure 3 and 4), and for some of the inclusions, there was a suggestion of secondary lysosomal association (Figure 4).
Microscopic studies of Procamallanus elatensis, a parasite in siganids, Red Sea fish in Egypt
Authors: Abdou N. , Heckmann R. A. , Gardner J. S. , Ashour A. A.
Published: June 2020

Camallanidae is a common nematode family found in a variety of Red Sea fish. Procamallanids were found to be specific to Siganus luridus and S. rivulatus which are considered to be commercially important fish. Procamallanus elatensis collected from Siganids in the northern Gulf of Elat were first described by Fusco and Overstreet using light microscopy, This report includes the first SEM description of Camallanid nematodes.

The parasites were washed in 7% saline and saved in 7% formalin until brought to Brigham Young University.They were washed with sodium cacodylate buffer (pH. 7.2), fixed in OSO4 for 12 hr, washed in cacodylate buffer, immersed into 2% tannic acid for 8 hr, washed in buffer, fixed again in OSO4 for 2 hr, washed in buffer, dehydrated with critical point drying and coated with gold.

Adult worms were long, slender, and reddish in color. At the anterior end the mouth was round and surrounded by the cephalic plate.
Immunoelectron microscopic studies of the muscle protein titin
Authors: Fassel Theresa A. , Greaser Marion L.
Published: June 2020

Titin, a skeletal and cardiac muscle protein, is almost 3 million daltons in mass and about 1μm in length. It extends approximately parallel to the long axis of the sarcomere from the Z line to the M line. A series of monoclonal anti-titin antibodies and a polyclonal anti-titin antibody were used to localize several titin epitope positions. A pre-embedding approach was used in which primary and secondary antibody incubations preceded chemical fixation, ethanol dehydration and LR White (room temperature infiltration, heat polymerization) or LR Gold (low temperature infiltration, ultraviolet light polymerization) processing for transmission electron microscopy. A post-embedding step provided a third layer of colloidal gold label. Monoclonal antibody incubations were followed by treatment with sheep anti-mouse IgG and finally with donkey anti-sheep IgG conjugated to 15 nm colloidal gold. Polyclonal antibody incubations were followed by biotinylated anti-chicken and streptavidin-gold (15 nm).

Rabbit psoas bundles were tied to glass capillaries in relaxing solution and incubated in a skinning solution for 6 hours at 4°C.
Cytochemical localization of ATPase activity in the leaves of a seagrass and a submerged halophyte
Authors: Barnabas A.D. , Coopoosamy M.
Published: June 2020

Flowering plants that grow submerged in seawater are known as seagrasses, while those that grow submerged in water of generally lower and varying salinity as in estuaries, are known as submerged halophytes. Knowledge of salt tolerance mechanisms in both groups of plants is important to our understanding of their biology. Recently, high ATPase activity was reported to be associated with the copiously-invaginated plasma membrane of leaf epidermal cells of a seagrass (Zostera marina), suggesting that ATPase played a role in salt regulation. In the present study, the seagrass Halophila ovalis and the submerged halophyte Ruppia maritima growing at salinities of 35°/00 and 25°/00 respectively, were used. The subcellular distribution of ATPase in leaf epidermal cells of both submerged aquatics was accomplished using a lead precipitation technique specific for ATPase activity. Lead deposits in the cells were an indication of sites of ATPase activity. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) microanalysis using a Joel 6100 SEM with a Noran Voyager 2100 EDX microanalyser, were used to study lead distribution. Ultrathin sections for the TEM were examined unstained.
Use of different human myeloid leukemia cell lines to determine the specificity of 3,3’-diaminobenzidine cytochemistry for the ultrastructural localization of myeloperoxidase and catalase
Authors: Boyd J. E. , Gilbert C. S. , Pinnix B. , Ballinger C. A. , Kinkade J. M. , Parmley R. T.
Published: June 2020

Myeloid cells are known to contain myeloperoxidase (MPO) and catalase. This study has used MPO and catalase replete and deficient myeloid cell lines to clarify the localization of these components using 3,3’-diaminobenzidine (DAB) ultrastructural cytochemistry. Conditions of DAB incubation can be modified to preferentially stain catalase (alkaline at pH 9.7) or MPO (neutral at pH 7.0-7.6), but crossreactivity persists, preventing the discrimination between catalase and peroxidase. Biochemical assays demonstrated both MPO and catalase in HL60 cells; similar amounts of catalase but no MPO activity in the A7 cell line; increased amounts of catalase but no MPO activity in the HP50 and HP100 cell lines; and neither MPO nor catalase in the KG1 cell line. Neutral DAB stained MPO (pH 7.4; [DAB] 5 or 20 mg/10 mL 0.05 M Tris; 30 min or 120 min; 24° or 37°C; 0.01% H2O2) in HL60 (Fig. 1), but not in A7. Alkaline DAB intensely stained catalase (pH 9.7; 20 mg/10 mL; 120 min; 37°C; 0.01% or 0.03%) in A7.
Benzyldimethylamine(BDMA) and dimethylaminoethanol as the catalysts of choice for epoxy resin embedding media
Authors: Mascorro J.A. , Kirby G.S.
Published: June 2020

INTRODUCTION: By long held tradition, many epoxy resin embedding media are catalyzed with 2,4,6-Tri(dimethylaminomethyl)phenol (DMP-30). Embedding media polymerized in this manner are widely-used and produce acceptable results, nevertheless they show high viscosity, a rapid loss in fluidity, and ultimately a shortened useful pot-life necessary for complete specimen infiltration. Perhaps using less viscous catalysts, such as Benzyldimethylamine (BDMA) or Dimethylaminoethanol (DMAE), would yield embedding media with lowered viscosity and prolonged fluidity, both very important characteristics that would ensure complete infiltration and strengthening of tissues subsequent to microtomy and ultrastructural study.

MATERIALS & METHODS: The amine catalysts BDMA, DMAE, and DMP-30 were tested for Average Flow Time (AFT) and Volume Flow Rate (VFR) by recording the time necessary for 9 ml of each component to flow from a vertically oriented viscosimeter. Viscosity (cp), which is a relative measure of fluidity and a real correlate of AFT/VFR, then was calculated with the Hagen-Poiseville relation for laminar flow as applied to fluids. Embed 812 and LX112 media were prepared and catalyzed either with BDMA, DMAE, or DMP-30 and their AFT, VFR, and cp similarly determined @ 5, 30, and 60 minute intervals after initial mixing.
Electron microscope tomography: 3-D reconstruction of asymmetric structures
Authors: Olins Ada L.
Published: June 2020

Computed axial tomography is a method used to obtain the internal, three-dimensional structure of a specimen from a series of two-dimensional projections. Our interest in chromosomal structures, which cannot be crystalized because of their size and apparent irregularity, led us to the application of tomography to electron microscopic data. Our specimens required observations of a large range of section thicknesses (0.1 μm to.75 μm), various magnifications (from 1 pixel = 7.5 nm to 1 pixel = 150 nm) and different volumes of reconstructed data ranging from 643 pixels3 to 5123 pixels3. The choice of parameters are determined by the size of the internal structure to be described.
Three-dimensional reconstructions from single oblique sections of rigor insect flight muscle
Authors: Taylor K. A. , Crowther R. A.
Published: June 2020

The oblique section 3-D image reconstruction method offers some advantages over techniques which combine multiple tilt views. A complete reconstruction, limited only by section thickness and geometry, is possible from a single image. Moreover, the reconstruction is insensitive to section thinning caused by prolonged electron irradiation, and the missing cone problem due to physical restrictions in specimen tilt is overcome. A major limitation is that sections must be thin relative to the unit cell dimension running approximately normal to the section plane.
Image quality vs data obtainment in biological electron microscopy
Authors: Johnson J. E.
Published: June 2020

In the early years of biological electron microscopy, scientists had their hands full attempting to describe the cellular microcosm that was suddenly before them on the fluorescent screen. Mitochondria, Golgi, endoplasmic reticulum, and other myriad organelles were being examined, micrographed, and documented in the literature. A major problem of that early period was the development of methods to cut sections thin enough to study under the electron beam. A microtome designed in 1943 moved the specimen toward a rotary “Cyclone” knife revolving at 12,500 RPM, or 1000 times as fast as an ordinary microtome. It was claimed that no embedding medium was necessary or that soft embedding media could be used. Collecting the sections thus cut sounded a little precarious: “The 0.1 micron sections cut with the high speed knife fly out at a tangent and are dispersed in the air. They may be collected... on... screens held near the knife“.
Application of ruthenium red/osmium tetroxide to bacteria, plant and animal tissue
Authors: Grayson R. L. , Rechcigl N. A.
Published: June 2020

Ruthenium red (RR), an inorganic dye was found to be useful in electron microscopy where it can combine with osmium tetroxide (OsO4) to form a complex with attraction toward anionic substances. Although Martinez-Palomo et al. (1969) were one of the first investigators to use RR together with OsO4, our computor search has shown few applications of this combination in the intervening years. The purpose of this paper is to report the results of our investigations utilizing the RR/OsO4 combination to add electron density to various biological materials. The possible mechanisms by which this may come about has been well reviewed by previous investigators (1,3a,3b,4).
Study of eukaryotic flagellar components by cryo-electron microscopy
Authors: Murray John M. , Ward Rob
Published: June 2020

The eukaryotic flagellum is constructed from 11 parallel tubular elements arranged as 9 peripheral fibers (doublet microtubules) and 2 central fibers (singlet microtubules). The primary motion generating component has been found to be arranged as axially periodic “arms” bridging the adjacent doublets. The dynein, comprising the arms, has been isolated and characterized from several different cilia and flagella. Various radial and azimuthal cross-links stabilize the axially aligned microtubules, and probably play some role in controlling the form of the flagella beat cycle.
Myofilament lattice of vertebrate skeletal muscle visualized by correlation averaging of frozen hydrated thin sections
Authors: Steven A.C. , Trus B.L. , Unser M. , McDowall A.W. , Dubochet J. , Podolsky R.J.
Published: June 2020

The structural basis of physiologically distinct states of muscle fibers - ‘rigor’, ‘relaxed', and active’, inter alia - lies in the differing set of interactions between the thick, myosin-containing, filaments and the interdigitating thin, actin-containing, filaments in the respective states. These spatial relationships are most directly perceived when the double hexagonal myofilament lattice is viewed in axial projection, as in transverse thin sections, or in density maps derived from equatorial X-ray diffraction. However, conventional thin sections are compromized by artifacts associated with chemical fixation, dehydration, and staining, and X-ray diffraction data, althouqh ‘native’, is limited by the lack of experimentally determined phases.
Ultrastructural and cell surface studies of cancer epidermal cells following vitamin E administration
Authors: Lupulescu A.P.
Published: June 2020

It has been postulated that vitamin E (α-tocopherol) plays an important role in the prevention and treatment of cancer. Thus, an inhibition of growth of melanoma cells in tissue culture, of NB cells in culture and in nude mice, was previously reported following vitamin E succinate administration. However, the exact mechanism of the antitumor activity of vitamin E is still unknown. The present study deals with the effects of natural vitamin E (α-tocopherol acetate) on the ultrastructure and cell surface of cancer cells from squamous cell carcinomas induced by 3-methylcholanthrene (MCA) in mice.
Effects of cisplatin treatment on the rat neurohypophysis
Authors: Fadool J.M. , Boyer P.J. , Aggarwal S.K.
Published: June 2020

Cisplatin (CDDP) is currently one of the most valuable antineoplastic drugs available. However, it has severe toxic side effects of which nephrotoxicity is the major dose limiting factor in its use. It induces morphological changes in the kidney with hampered urine output. The present study is an effort to determine the influence of the drug on the neurohypophysis for any antidiuretic effects on the kidney.
Cytochemistry and morphometry of rat sciatic nerve following laser and suture treatments
Authors: Shah A. , Bailes J. E. , Sahgal V. , Cerullo L. J.
Published: June 2020

The success of nerve repair treatment can be measured by examining the factors (Wallerian degeneration) that prevent functional recovery, and determining the extent of regeneration of proximal axon sprouts in the endoneurial environment of the distal fascicles. In the present study, the neurosurgical alignment of fascicles was attempted by laser as well as suture microsurgery of transected rat sciatic nerve and the relative efficacy of the two procedures was evaluated after 6 and 12 weeks by Neurophysiological Study, Morphological Study with light microscopy, ultrastructure, and the permeability of blood-nerve barrier using horseradish peroxidase (HRP) tracer technique, and Morphometry of the nerve fibers.
Acetaminophen: Abortifacient and embryocidal action
Authors: Poolsawat S.S , Huerta C.A.
Published: June 2020

Introduction. Chemical toxicity in the U.S. affects approximately 40% of the nation's 80 million workers who are exposed to toxic chemicals on a full or part-time bases. In 1980, about 40% of this workforce was comprised of women of childbearing ages. Considering such figure of a large number of women exposed to chemical toxins, it is a wonder that we have not had an epidemic of birth defects and organ abnormalities. A study has pointed that about 40% to 50% of all conceptions are eliminated before week 20 of gestation by way of a safety mechanism which helps to reduce the number of birth defects Acetaminophen, considered the safest of all over-the-counter analgesics, has been reported to induce fatal liver necrosis in man and animals.
Fascicles of hemoglobin S fibers
Authors: McDade William A. , Vassar Robert J. , Josephs Robert
Published: June 2020

The substitution of valine for glutamic acid at the β 6 position of hemoglobin results in a mutant protein whose solubility is dramatically decreased in the deoxygenated form. The deoxygenated protein polymerizes to form long, solid helical rods called fibers. The red blood cells of sickle cell anemia patients are filled with these fibers that distort the cell into the rigid shapes pathognomonic for the disease. In stirred solutions of purified HbS, fibers are the first of a series of metastable intermediates that ultimately crystallize. Fibers have the potential to form either larger particles, called macrofibers, or bundles, called fascicles.
The restoration of blurred electron micrographs
Authors: Carragher Bridget , Bluemke David A. , Potel Michael J. , Josephs Robert
Published: June 2020

We have investigated the feasibility of restoring blurred electron micrographs. Two related problems have been considered; the restoration of images blurred as a result of relative motion between the specimen and the image plane, and the restoration of images which are rotationally blurred about an axis. Micrographs taken while the specimen is drifting result in images which are blurred in the direction of motion. An example of rotational blurring arises in micrographs of thin sections of helical particles viewed in cross section. The twist of the particle within the finite thickness of the section causes the image to appear rotationally blurred about the helical axis. As a result, structural details, particularly at large distances from the helical axis, will be obscured.
Scanning electron microscopic study of collagen fibrillogenesis and extracellular compartmentalization in the chick embryo tendon
Authors: Yang Grace C.H.
Published: June 2020

The size and organization of collagen fibrils in the extracellular matrix is an important determinant of tissue structure and function. The synthesis and deposition of collagen involves multiple steps which begin within the cell and continue in the extracellular space. High-voltage electron microscopic studies of the chick embryo cornea and tendon suggested that the extracellular space is compartmentalized by the fibroblasts for the regulation of collagen fibril, bundle, and tissue specific macroaggregate formation. The purpose of this study is to gather direct evidence regarding the association of the fibroblast cell surface with newly formed collagen fibrils, and to define the role of the fibroblast in the control and the precise positioning of collagen fibrils, bundles, and macroaggregates during chick tendon development.
Application of high pressure freezing and freeze fracture to study dynamic events in plant cells
Authors: Craig Stuart , Staehelin L.A.
Published: June 2020

Specimen preparation, in particular chemical fixation, is usually the limiting factor in studies of dynamic intracellular events by electron microscopy. The main drawbacks of chemical fixation are slow mode of action (immobilization of cellular structures requires seconds to minutes) and selectivity of chemical reactivity (different molecules are inactivated at different rates). Thus, chemical fixation is much slower than many transient cellular phenomena and cannot be used to obtain reliable structural data on such events. Ultrarapid freezing can overcome these problems. The most successful ultrarapid freezing methods are "slam" and propane jet freezing.
Cell monolayer technique using sectionable culture beads
Authors: Hogan Margaret E.
Published: June 2020

The use of tissue culture, as an experimental model, has gained high regard in the study of organism function and control. For this reason the ability to observe these cells has become quite important in both transmission(TEM) and scanning electron microscopy(SEM).

Most monolayers of cells have been grown on flat substrates (culture plates and flasks), and have required involved manipulation to prove the desired plane of sectioning. With the use of culture beads much of the handling is eliminated, in fact the procedure is really no different than preparing whole tissue for electron microscopy. Along with the ease of preparation, the beads provide increased tissue per section, and therefore a more broad sampling of the specimens.
Ruthenium tetroxide fixation comparison of bacterial surface ultrastructure
Authors: Caughey R. C. , Miller M. A.
Published: June 2020

Ruthenium tetroxide is known to improve overall contrast and preservation of membranes. It is a cationic dye which has an affinity for strongly positive anionic polymers and thus more effectively preserves exopolysaccharide materials such as glycocalyx on bacterial membrane surfaces. This study was undertaken to determine the usefulness of this technique over conventional fixation procedures in the study of bacterial surface structures that are important in pathogenicity.

Different strains of pathogenic bacteria (possessing various surface structures) were routinely fixed in 2.5% glutareldehyde and 1% osmium tetroxide, dehydrated in a graded series of ethanols, and embedded in Epon 812 epoxy resin. Half of each sample was fixed in 0.05% ruthenium tetroxide (pH7.1) instead of osmium tetroxide, and then dehydrated and embedded as above. All of the samples were sectioned and post stained in uranyl acetate/lead citrate.
The density of neurofilaments differs in the somatic motor and parasympathetic oculomotor axons of chickens
Authors: Price R. L. , Paggl P. , Lasek R.J.
Published: June 2020

The rate of neurofilament transport in somatic oculomotor axons is 2-3 times faster than 1t 1s in the preganglionic parasympathetic oculomotor axons of young chickens. The rate of neurofilament transport may be influenced by the lateral interactions between neurofilaments. To determine whether the lateral Interactions between neurofilaments differs between the somatic motor and the parasympathetic axons, we determined the neurofilament density 1n these axons.
Ultrastructure of primary spermatocyte in fish (Tilapia: Oreochromis niloticus): The synaptonemal complex
Authors: Guha T. , Siddiqui A. Q. , Prentis P. F.
Published: June 2020

The Primary Spermatocytes represent a stage in spermatogenesis when the first meiotic cell division occurs. They are derived from Spermatogonium or Stem cell through mitotic division. At the zygotene phase of meiotic prophase the Synaptonemal complex appears in these cells in the space between the paired homologous chromosomes. Spermatogenesis and sperm structure in fish have been studied at the electron microscope level in a few species? However, no work has yet been reported on ultrastructure of tilapia, O. niloticus, spermatozoa and spermatogenetic process. In this short communication we are reporting the Ultrastructure of Primary Spermatocytes in tilapia, O. niloticus, and the fine structure of synaptonemal complexes seen in the spermatocyte nuclei.
Comparative ultrastructural pathology of methyl mercury-induced lesions in a teleostean and a mammalian cell line
Authors: Crooker A. R. , Devlin E. W. , Johnson D. E. , Mottet N. K.
Published: June 2020

Toxic organic mercury compounds, especially methyl mercury (MeHg), have been responsible for severe environmental contamination. Industrial effluents of inorganic or metallic mercury are methylated by aquatic organisms leading to transfer and bioconcentration of MeHg up the food chain to fish and man. In vivo mammalian and teleostean (bony fish) models have provided useful data on mercury toxicity; cultures of animal cells have been used to investigate the toxic actions of heavy metals such as mercury. The present study was designed to determine if RTG-2 cells, a fibroblast-like line derived from rainbow trout (Salmo gairdneri) gonads, would provide a highly controlled system in which to study the mercury-cell interaction. A mammalian cell line derived from Chinese hamster ovary (CHO)2 and known to be sensitive to MeHg3 was chosen as a positive control. The specific objective was to determine the effect of MeHg on RTG-2 and CHO cell viability and ultrastructure.
Effect of carbon monoxide exposure on the ultrastructure of cardiac muscle cells in culture
Authors: Nag A.C. , Chen K.C. , Cheng M.
Published: June 2020

Cardiac muscle cells in culture have been used as a model system for various kinds of structural and biochemical studies. It is known that CO affects oxygen transport to the organ system of the body by binding with blood hemoglobin to form carboxyhemoglobin and causes an overall tissue hypoxia. The effects of various concentrations of CO on the ultrastructure of myofibrils and mitochondria are examined in embryonic cardiac myocytes during differentiation in culture without complicating factors derived from the presence of a vascular supply system.
Simulations for surface profile imaging
Authors: Lu Ping , Smith David J.
Published: June 2020

Recent experimental micrographs suggest that the technique of surface profile imaging at atomic resolution offers the prospect not only for establishing the nature of many surface reconstructions but also for determining the connection between surface and bulk structure, in particular the extent of any surface relaxations. Image simulations have so far been used to confirm the interpretability of profile images of gold and silicon. We report here our further investigations for two compound materials, namely the ceramic uranium oxide and the semiconductor gallium arsenide. Various through-focal, through-thickness series have been simulated, primarily for a 400keV microscope with Cs= 1.0mm, focal spread 10 nm and semiangle 0.5 mr. The multislice part used the FFT method, typically with 128k Fourier coefficients: the imaging section included the envelope functions as real space sums. The output was photographed directly from a video monitor.
In situ HREM observation of interphase boundary motion in 95Pb-5Sn solder
Authors: Posthill J.B. , Frear Darrel , Morris J.W.
Published: June 2020

The use of solder to provide mechanical attachment and electrical interconnection for electronic packaging is widespread throughout the industry. One application for a lead-rich solder is in the IC chip/ceramic carrier connection. It is well-established that this joint is susceptible to thermal-fatigue failure and, hence, a thorough microstructural study is warranted. Previous work has shown that 95Pb-5Sn contains β-Sn precipitates that have formed upon solidification and subsequent aging at ambient temperature. Diffraction contrast TEM demonstrated that the precipitates lie on {111}pb habit planes. High-resolution electron microscopy was undertaken to establish whether or not the habit plane was faceted on the atomic level. This contribution reports on an observation of beam-induced precipitate dissolution.
High-resolution electron microscopy of the atomic structure of some grain boundaries in Au
Authors: Krakow W. , Smith D. A.
Published: June 2020

The successful determination of the atomic structure of [110] tilt boundaries in Au stems from the investigation of microscope performance at intermediate accelerating voltages (200 and 400kV) as well as a detailed understanding of how grain boundary image features depend on dynamical diffraction processes variation with specimen and beam orientations. This success is also facilitated by improving image quality by digital image processing techniques to the point where a structure image is obtained and each atom position is represented by a resolved image feature. Figure 1 shows an example of a low angle (∼10°) Σ = 129/[110] tilt boundary in a ∼250Å Au film, taken under tilted beam brightfield imaging conditions, to illustrate the steps necessary to obtain the atomic structure configuration from the image. The original image of Fig. 1a shows the regular arrangement of strain-field images associated with the cores of ½ [10] primary dislocations which are separated by ∼15Å.
Phase separation in Fe9S10 crystal
Authors: Nguyen Thao A. , Hobbs Linn W.
Published: June 2020

The low temperature phase relation of iron sulfide compounds Fe1-xS, with composition ranging from FeS to Fe7S8, has been investigated extensively over the past several decades. Despite these efforts conflicting reports on the stability of low temperature phases still exist and major disagreements between proposed phase diagrams remain unresolved. In this paper we report preliminary findings of our effort to determine whether the low temperature iron sulfide compounds form a homologous series Fen-l,Sn n≥ 8 [1] or a solid solution [2]. We have examined the stability of iron sulfide crystal of composition Fe9S10 using in situ heating experiment and image contrast transmission electron microscopy. We have found that Fe9S10 decomposes to two distinct phases. These two phases are labelled as H and K phases.
Thin films for radiation control in boiling water nuclear reactors
Authors: Vook R. W. , Rao T.V. , Swirbel T. , Bucci J. , Meyer W.
Published: June 2020

Boiling water nuclear reactors (BWR's) experience radioactive film buildup on the inner walls of their out-of-core stainless steel (S.S.) cooling water pipes. These films consist of various oxides of Fe, Cr, and Ni, and contain small amounts of radioactive Co-60. As a result the pipes must be decontaminated or replaced periodically. Efforts are currently being made to passivate these S.S. surfaces so as to reduce the rate of radiation buildup. In the present work, the effects of various protective metallic thin film coatings on the morphology of the radioactive oxide film grown in a simulated BWR test loop are reported.
An atomic resolution study of precipitates in an Al-Ge Alloy
Authors: Dahmen U. , Nelson C. , Westmacott K.H.
Published: June 2020

The difficulty of precipitating germanium in dilute aluminum-germanium alloys is due to a large difference in crystal structures (face-centered cubic and diamond cubic) accompanied by a substantial volume expansion of 36%. A great variety of precipitate morphologies and orientation relationships are observed. A frequently found morphology is that of <100> needles. By selected area diffraction and Moire fringes it has been established that <100> Al and <110> Ge are parallel along the needle axis. The typical aspect ratio of about 100 has made it difficult in the past to investigate the cross-sectional shape and internal structure of these needles, although some indications of internal twinning were found in plates. in the present work, the Berkeley Atomic Resolution Microscope was used to examine needles in cross section by imaging along the <110> Ge <100> Al needle axis.
TEM study of dislocation array/high angle grain boundary interaction in type 304 stainless steel
Authors: Wise Cynthia M.
Published: June 2020

The interaction of dislocations with grain boundaries is considered a controlling process for many of the mechanical properties, including strength in a metal. The grain boundary acts as a barrier to impede the motion of dislocations, and strengthens the material because of the increased stress necessary to induce slip propagation.

TEM samples were prepared from type 304 stainless steel which was solution treated, lightly deformed, electropolished using standard techniques, and examined in a JEOL 200CX TEM operating at 200KeV, using a double-tilt goniometer stage.
Ultra-high-vacuum, high-resolution Transmission Electron Microscopy at 400 kV
Authors: Ponce F. A. , Suzuki S. , Kobayashi H. , Ishibashi Y. , Ishida Y. , T. Eto
Published: June 2020

Electron microscopy in an ultra high vacuum (UHV) environment is a very desirable capability for the study of surfaces and for near-atomic-resolution imaging. The existence of amorphous layers on the surface of the sample generally prevents the direct observation of the free surface structure and limits the degree of resolution in the transmission electron microscope (TEM). In conventional TEM, these amorphous layers are often of organic nature originating from the electron bombardment of hydrocarbons in the vicinity of the sample. They can in part also be contaminants which develop during the specimen preparation and transport stages. In the specimen preparation stage, contamination can occur due to backsputtering during the ion milling process. In addition, oxide layers develop from contact to air during transport to the TEM. In order to avoid these amorphous overlayers it is necessary: i) to improve the vacuum of the instrument, thus the need for ultra high vacuum; and ii) to be able to clean the sample and transfer it to the column of the instrument without breaking the vacuum around the sample.
The twin lens system - A high resolution objective lens at 300 kV
Authors: Bormans B. , Hagemann P.
Published: June 2020

Point resolution of better than 0.2 nm is today achievable in medium voltage electron microscopes. Crucial for this achievement is the objective lens design which has to provide sufficiently low spherical and chromatic aberration figures. In addition to the lens itself, its integration into the overall microscope optics has to ensure a reproducible and accurate alignment.

Cleaver has shown that symmetrical lenses have lower aberrations than their asymmetrical counterparts by a factor of 1.5 or 2. Theoretical optimization of this lens at 300 kV can be carried out using a first-order finite element program, as developed by Munro. The symmetrical single-field condenser objective with saturated pole-piece tips produces particularly good values with Cs = 1.0 mm and Cc = 1.4 mm at 300 kV. In this lens the specimen is placed in the centre of the magnetic field.