bluuebunny/crossref_metadata_2025_split huggingface dataset:
Specimen preparation, cryotransfer and microscope parameters for cold-stage work in SEM and application for the physical and biological sciences
Authors: Sargent J.A. 
Published: June 2020

The availability of equipment which enables frozen-hydrated material to be viewed over prolonged periods in the SEM has greatly extended the versatility of the instrument and permitted more precise interpretation of the data obtained from it. Artifacts associated with chemical fixation are avoided and soluble components are retained which might otherwise be removed by solvents used for dehydration or critical point drying. In addition the shrinkage which frequently occurs during freeze drying is avoided. Two further advantages of cryo preservation can be invaluable: rapid cooling of motile specimens instantly arrests movement and the immobilization of diffusible compounds and ions enables X-ray microanalysis to be performed with confidence.The speed with which specimens are cooled is not critical if only surface features are to be studied. However, the examination of internal structure demands that ice crystal growth be minimised. Devices are available to maximise cooling rates using a variety of cryogens and specimen transfer to the SEM cold stage is achieved simply and effectively.
Molecular microscopy: Theoretical possibilities and experimental realities
Authors: Sidles John A. 
Published: June 2020

It is interesting to imagine a world in which microscopy had never been invented. What techniques would scientists use to study cell structure? Lack of microscopy would not prevent research.... instead scientists would study cells using indirect means; e.g. by homogenizing, filtering, and centrifuging cells. After much work, they would be able to demonstrate that cells are surrounded by membranes, and contain nuclei carrying genetic information. All aspects of cell structure could be studied in this indirect way.Biomedical researchers would not feel particularly handicapped by the lack of microscopy. Rather they would compete for access to the newest and most ingenious filtering devices. In this hypothetical world, it would not be readily apparent that instrument technology was a crucial medical/scientific issue.It is arguably the case that we live in a similar world, and that (from a clinical perspective) we need a microscope technology that can image 3D biomolecular structure with the subangstrom spatial resolution that is required for the rational design of drugs and vaccines.The highest-resolution techniques for determining 3D molecular structure are x-ray crystallography and mutidimensional NMR analysis. However, neither of these techniques can properly be called “microscopy”.
Effect of brefeldin A (BFA) on the unique surface coat of pulmonary intravascular macrophages (PIMs) of sheep: Ultrastructural and cytochemical study
Authors: Singh Baljit 
Published: June 2020

The PIM of sheep, calf, goat and horse has a characteristic ultrastructural feature in the form of a unique, heparin sensitive, globular surface coat present around the plasma membrane with an intervening electron lucent space of 32-40 nm. We previously showed the active involvement of this surface coat in the phagocytosis of tracer material like monastral blue and cationized ferritin. The surface coat is capable of reconstitution in vivo following disruption with heparin. The present study was aimed to investigate whether PIM is the source of surface coat or not. In the recent years the BFA has been extensively used to understand the secretory pathways in the cells because of its ability to cause a rapid and reversible block to the anterograde transport of proteins from the endoplasmic reticulum to the Golgi.Sheep (n=6) were weighed, their plasma volume was calculated indirectly and based on which a sufficient single intravenous dose of BFA was given so as to reach a concentration of 4-5 microgram/ml of plasma.
Enhanced axial resolution of the cytoskeleton in fluorescence microscopy by standing-wave excitation
Authors: Lanni Frederick , Bailey Brent , Farkas Daniel L. , Lansing Taylor D. 
Published: June 2020

When the depth-of-field of a microscope is less than the axial dimension of the specimen, 3d information can be derived from a set of images recorded as the specimen is stepped through the object focal plane of the microscope. This procedure, known as optical sectioning microscopy (OSM), is the same in direct imaging and confocal scanning. For both of these cases in fluorescence microscopy, axial (depth) resolution is more limited than transverse resolution, for fundamental reasons. Our research aim has been to enhance axial resolution in fluorescence OSM (FOSM) while retaining the high-speed information transfer characteristics of direct imaging that are necessary for 3d studies of living cells in culture.Standing-wave fluorescence microscopy (SWFM) is a direct imaging method in which the object is illuminated by a three-dimensional field of planar interference fringes (standing waves) oriented parallel to the focal plane of the microscope. This field is produced in the specimen by crossing two coherent, collimated, s-polarized beams of equal amplitude directed through the specimen at complementary angles (θ, π -θ) relative to the axis of the microscope.
Cryo-electron microscopy of human erythrocyte membrane skeletons
Authors: Li Li , Josephs Robert 
Published: June 2020

The membrane skeleton is a two-dimensional network of structural proteins attached to the cytoplasmic surface of the erythrocyte membrane. Spectrin, actin and band 4.1 are the major components in the skeleton network. It is generally believed that the membrane skeleton plays an important role in the deformability and stability of red cells. In this work we have used cryo-electron microscopy to examine the effect of ionic strength on skeleton size. Since the skeletons were unstained, unfixed and hydrated drying effects and the attendant changes in salt concentrations and pH associated with negative staining did not affect our results. The skeletons were embedded in a thin layer of vitreous ice supported by a fenestrated carbon film, which provided higher contrast than fenestrated carbon grids.Ghosts derived from normal human red cells were incubated with 4 volumes of 2.5% Triton X-100 in 5 mM sodium phosphate (pH 7.4) for 1 hour at 4°C. The mixture was layered on top of a discontinuous density gradient of 10% and 60% sucrose. After centrifugation, the membrane skeletons were collected and dialyzed against 0.2 mM or 5 mM sodium phosphate buffer (pH 7.4) for 4-6 hours.
Correlative light and electron microscopy: Counting centrioles in individual sea urchin zygotes previously followed in vivo
Authors: Sluder Greenfield , Miller Frederick J. 
Published: June 2020

Centrosomes are the ensembles of structures that define the poles of the mitotic apparatus. In animal cells, a centrosome typically consists of a pair of orthogonally arranged centrioles associated with osmiophilic pericentriolar material which nucleates the microtubules of the aster and central spindle. The precise doubling, or reproduction, of the centrosome during interphase is an important event in the cell’s preparations for mitosis.To characterize the mechanisms that control centrosome reproduction we need to follow the behavior of centrosomes within individual cells over several cell cycles. We use sea urchin zygotes as an experimental system because they have a rapid cell cycle, are large enough (100 um diameter) to easily manipulate, and are optically clear. However, the experiments pose two challenges. The first is to follow the behavior of centrosomes within individual zygotes for several hours with the light microscope and then recover just those individuals from a large population for ultrastructural analysis.
A rapid silver-impregnation technique on ultra-thin sections for Electron Microscopy
Authors: Chien K. , Heusser R.C. , Jones M.L. , Van de Velde R.L. 
Published: June 2020

Silver impregnation techniques have been used for the demonstration of the complex carbohydrates in electron microscopy. However, the silver stains were believed to be technically sensitive and time consumming to perform. Currently, due to the need to more specifically evaluate immune complex for localization in certain renal diseases, a simplified procedure in conjunction with the use of the microwave has been developed and applied to renal and other biopsies. The procedure is as follows:Preparation of silver methenamine solution:1. 15ml graduated, clear polystyrene centrifuge tube (Falcon, No. 2099) was rinsed once with distilled water.2. 3% hexamethylene tetramine (methenamine) was added into the centrifuge tube to the 6ml mark.3. 3% silver nitrate was added slowly to the methenamine to the 7ml mark while agitating. (Solution will instantly turn milky in color and then clear rapidly by mixing. No precipitate should be formed).4. 2% sodium borate was added to the solution to the 8ml mark, mixed and centrifuged before use.
High-performance EM-002B optical column construction for future expansion
Authors: Shirota K. , Moriyama K. , Mikami S. , Ando A. , Nakamura O. , Yanaka T. 
Published: June 2020

Since modern analytical transmission electron microscopes must have a wide range of illumination conditions (from “mm” to “nm” probe size), an additional lens (one of the condenser lenses, usually called the “mini-lens”) is arranged immediately above the objective lens pole pieces. As a result, it has become very difficult to install an exchange mechanism for the objective pole pieces, which used to be done routinely.To overcome this, TOPCON Electron Microscope EM-OO2B incorporated a new mechanism which can be exchanged quite easily and reliably by the user. This mechanism makes a space to exchange pole pieces, without column disassembly, by precisely driven external mechanisms (Fig. 1). The time required for a typical user to carry out such exchange is usually 15 to 20 minutes, and it will take not more than two hours for high resolution image or analysis after exchange. This time is also shortened by the fact that an anti-contamination cold trap is not generally required in the case of EM-OO2B.
Cytochemical localization of glycogen phosphorylase activity in rat liver
Authors: Michaels John E. , Cardell Robert R. 
Published: June 2020

Glycogen phosphorylase (GP) is a key enzyme in liver glycogen breakdown. GP activity is altered with its state of phosphorylation. In the current study, the intralobular distribution of GP activity was observed histochemically in frozen sections of rat liver during fasting and after stimulation of glycogen synthesis.Normal and adrenalectomized (ADX) rats were fasted overnight to reduce liver glycogen to minimal levels. Fasted ADX rats received 2 mg dexamethasone (DEX) 0-8 h prior to sacrifice to stimulate glycogen synthesis. Liver was removed, rapidly frozen in isopentane cooled in liquid nitrogen, then cryostat sectioned. In order to determine sites of GP activity, sections were incubated in medium that contained glucose 1-phosphate as substrate. Under the incubation conditions used, GP synthesized glycogen as the reaction product. Glycogen was identified by two staining methods: 1) iodine staining has been shown to be rather specific for newly synthesized glycogen produced during the histochemical procedure (Figs.1-6), whereas 2) periodic acid-Schiff (PAS) stained both native and nascent glycogen.
Immunogold electron microscopic localization of phosphoenolpyruvate carboxykinase in rat liver
Authors: Gao Kuixiong , Morris Randal E. , Giffin Bruce F. , Cardell Emma Lou , Cardel Robert R. 
Published: June 2020

Phosphoenolpyruvate carboxykinase (PEPCK) is a rate-limiting gluconeogenic enzyme which catalyzes the conversion of oxaloacetate to phosphoenolpyruvate. A gradient of PEPCK from periportal hepatocytes to pericentral hepatocytes has been demonstrated in normal rat liver; however, the subcellular distribution of PEPCK molecules within hepatocytes could not be determined from these light microscope studies.We have used two immunogold histochemical approaches to study the subcellar distribution of PEPCK in normal rat hepatocytes. In the first procedure 10μm cyrosections of 4% paraformaldehyde perfusion-fixed rat liver were collected on silanated slides and immunostained with goat anti-rat PEPCK (normal goat serum served as a control), and incubated in a secondary antibody (5nm gold-labeled rabbit anti-goat IgG) and a tertiary antibody (5nm gold-labeled goat anti-rabbit IgG). The immunogold stained samples, with or without silver enhancement (IGSS), were counterstained with pyronine Y, re-embedded in Visio- Bond and removed from the slides and semithin sectioned for epipolarized illumination combined with transmitted light microscopy (Figs. 1 and 2), or re-embedded in epoxy resin and sectioned for electron microscopy (EM, Fig. 4) In the second procedure 25, 50 and 100 μm free-floating vibratome sections of well fixed rat liver (4% paraformaldehyde plus 0.5% glutaraldehydeperfusion-fixed, immersion fixed overnight at 4°C) were immunogold stained using a 5nm gold labeled secondary antibody, with and without IGSS, osmicated, embedded in epoxy resin and sectioned for EM (Figure 3).
Pathology of the spermatic middle piece and infertility
Authors: Gallegos de L. G. , Ramírez B. E. , Gómez G. L. , Diaz G. M. 
Published: June 2020

On the pathology of spermatozoa associated to infertility, it has been described a variety of alterations that include subtle axonemal defects such as lack of dineyn arms, and altered microtubular pattern (9+0). Also it has been reported acrosomal agenesy in round head sperms, and altered acrosomal modelation. All these alterations become responsible of sperm motility disarrangement that impair procreation. In these cases it is convenient the ultrasructural study with the purpose of a more correct and precise diagnosis and prognosis.Thus, we studied the subcellular spermatic pathology in semen of infertile men obteined by masturbation. The specimens were proccesed for electron microscopy by the usual method, after washing in phosphate buffer. Thin sections were observed in Carl Zeiss EM 109 electron microscope.In this series of 21 patients studied, 43% have showed alterations of the flagellar middle piece. At the optical microscope, the sperms showed short tail and were immotile or presented a big cytoplasmic drop and movement grade I or II (according to WHO classification).
Soybean chloroplast responses to enhanced ultraviolet irradiation
Authors: Crang Richard F.E. , Vassilyev Audrey E. , Miroslavov Yevgeney A. 
Published: June 2020

Environmental concerns over the degradation of the earth’s stratospheric ozone layer have been expressed for the past decade in recognition that with ozone depletion, enhanced ultraviolet irradiation will be received at the earth's surface. Such increase in ultraviolet irradiation can be hypothetically determined by making appropriate computer calculations based on proposed cloud cover, season, latitude, elevation, and percent of stratospheric ozone depletion. We have proposed a 40% reduction in the ozone layer corresponding to a daily increase of 19.1 kJ in the limits of ultraviolet-B (UV-B) spectral irradiation (280-320 nm). This is within the range of realistic possibilities based on current estimated ozone depletion rates for the next 40-50 years. We wish to determine the extent to which chloroplasts are ultrastructurally altered compared with those from plants raised under ambient conditions lacking an UV-B irradiation component.Uninoculated seeds of soybean (Glycine max), cv. “Forrest” were sown in standardized greenhouse soil in 4" clay pots, watered daily, and fertilized once per week.
Structure of seeds and developing seedlings of Hydrilla verticillata
Authors: Holmberg D. L. , Ryan F. J. 
Published: June 2020

Until recently, it was believed that Hydrilla verticillata, a widespread aquatic weed, did not generally produce seeds. There were reports that the monoecious biotype from the U. S. was sometimes capable of producing viable seeds, although these were not described in any detail. Recent work at the USDA ARS Aquatic Weed Research Laboratory, Ft. Lauderdale, FL, identified a monoecious biotype of H. verticillata from Penang Island (Malaysia) that is self-fertile and reliably produces viable seed. This biotype may also be crossed with other biotypes including the female dioecious plant from Florida. This work was undertaken to describe the anatomical characteristics of seeds and developing seedlings, using light and electron microscopy.Seeds and seedlings of the Penang Island biotype and Florida X Penang Island cross were processed for light and scanning electron microscopy (SEM). Fixed and fresh material was used. Seeds and seedlings were fixed in 2% paraformaldehyde and 0.1% gluteraldehyde in 0.1M phosphate buffer, pH 7.0. and dehydrated to 100% ethanol.
Use of low-voltage SEM (LVSEM) to evaluate cellular morphology and extracellular polysaccharide production by Pseudomonas fragi (ATCC 4973), Listeria monocytogenes (scott A), and Salmonella typhimurium
Authors: Schwach Tina , Zottola E. A. 
Published: June 2020

LVSEM offers the microbiologist a unique view of the microbial cell surface. Colony morphology is used by microbiologists to distinguish between organisms. Some bacteria exhibit different colony morphologies when grown on solid media. P. fragi ATCC 4973 exhibits both rough (R) and smooth (S) colonies. It is not known why different morphologies form, but there is some speculation that their expression may be affected by nutrient conditions,other physical parameters, such as growth in a nonstatic environment, and may involve extracellular polysaccharide (EPS) formation. EPS has also been implicated in bacterial attachment to surfaces.In this study, three organisms of importance to the food industry were grown in Trypticase Soy Broth (TSB) at 21C. Growth rates, EPS production, and cell surface morphologies were evaluated in both 3% TSB and 0.3% TSB. The lower concentration was used to simulate decreased availability of nutrients. Two glass chips (3mm × 6mm) were added to small petri dishes containing the culture medium and the organism.
Role of Kupffer cells in CCl4-induced hepatocytic toxicity: A preliminary study
Authors: Yamashiro S. , Bast T. , Towner R.A. , Janzen E.G. , Reinke L.A. 
Published: June 2020

Carbon tetrachloride (CCl4) hepatotoxicity is one of the most frequently used experimental models to study the mechanism of cell damage by metabolites of xenobiotics (1,2). Cytochrome P-450 enzymes are considered to be involved in the metabolic activation of CCl4 to generate the trichloromethyl (.CCl3), which in turn may be converted to the peroxy radical (.00-CCl3) (3,4). In our previous studies, we have demonstrated CCl4-induced edematous response by using proton magnetic resonance imaging and electron microscopy (2,5). However, these studies have not given any consideration to Kupffer cells, which could act as an interphase between the sinusoid and hepatocytes.Three male Wistar rats (200-250 g) were given two doses of CCL4 one hour apart (160 μl/kg bodyweight, with 5% Emulphor in 0.85% saline) intraperitoneally (i.p.). The same number of rats received phenyl tert-butyl nitrone (PBN), 25 mg/200 g in a 0.07 M pH 7.4 phosphate buffer and corn oil i.p. 30 min prior to the administration of CC14 as above.
Human, bovine, and pig teeth surface characterization of enamel and dentin: An SEM study
Authors: Fortin Daniel 
Published: June 2020

Many researchers use extracted human teeth to evaluate the adhesive strength of restorative materials. Attachment to tooth hard tissues in the oral cavity is a complex and difficult problem that has challenged investigators. An important step in dealing with this problem is a thorough characterization of the substrate. Extracted human teeth are, however, becoming increasingly difficult to obtain due to recent progress in conservative dental treatment. Other mammalian teeth, such as bovine teeth have been tested. Although slightly different in composition and structure, bovine teeth have been used as substitute for human teeth and their use has been documented in different papers. While using such teeth does not lead to results that are identical with those obtained when the enamel and dentin of human teeth is used, they do produce results that are comparable and certainly useful in evaluating the influence of various methods of enamel and dentin treatment.In order to find a substitute for human teeth in laboratory studies, surface characterization of enamel and dentin from bovine and pig teeth were compared using the SEM to human teeth.
Electron Microscopic study of inner ear of guinea pig with special reference to morphological changes in vestibular macula in hypercholesterolemia
Authors: Qiao Yan , Asano Goro , Kashiwado Izumi , Hattori Yasuo 
Published: June 2020

Vertigo may be induced by various factors such as vascular changes including arteriosclerosis and hypercholesterolemia in the inner ear. In orter to clarify the mechanism of vertigo, the inner ear of guinea pig in hypercholesterolemia condition was investigated by electron microscopic techniques.The guinea pigs have served as experimental materials. They were divided into two groups: one received non-administration of cholesterol and the other received the administration of cholesterol. The vestibular macula in inner ear were observed at 1, 2 and 3 months after the administration of cholesterol and also vascular function was investigated by using horseradish peroxidase as tracer.Ultrastructural changes such as the depletion of microvilli on the cell surface and increased microvesicles were detected in the cytoplasm of sensory cell after cholesterol administration. After two months, lipid droplets were demonstrated in the cytoplasm, associated with intercellular edema. The cytoplasmic projection with vacuolization was demonstrated in the surface of sensory cells in the vestibular macula after three months of cholesterol administration.
Ultrastructural changes in the cochlea of the inner ear in guinea pigs with hypercholesterolemia
Authors: Kashiwado Izumi , Yuge Kurata , Hattori Yasuo , Qiao Yan , Asano Goro 
Published: June 2020

Although sensory neural hearing loss stemming from hypercholesterolemia has received attention in recent year, nothing has been made known about inner ear injuries resulting from this condition.In this study, we prepared guinea pig models with hypercholesterolemia and observed inner ear with a transmission electron microscope, and also investigated the effect of vitamin E therapy on injuries.Materials and Methods: Ninetyth white female Hartley guinea pigs weighing 250-300g each were divided into three groups. Group A consisted of the control animals, which were fed by a stock diet. Group B was fed by a hyperlipid diet (2.5% cholesterol, 0.25% bile acid, and 7.5% cattle fat). Group C was given a vitamin Eadded hyperlipid diet. All animals were sacrificed at either one, two or three months after treatment, and cochlear duct vasculature was observed with a transmission electron microscope. Cholesterol, triglyceride, and TBARS values were concurrently measured in serum.Results: In group B and C, cholesterol and triglyceride levels remainedon control levels. The TBARS level was elevated in group B but remained unchanged in groups A and C.