bluuebunny/crossref_metadata_2025_split huggingface dataset:
Difference fourier maps reveal structural changes for intermediates in the bacteriorhodopsin photocycle
Authors: Glaeser R. M. , Han B.-G. , Hendrickson F. M. , Vonck J. 
Published: June 2020

Bacteriorhodopsin (bR) is a light-driven proton pump that exists in the cell membrane of halobacteria. Proton pumping across the membrane is achieved through a photochemical cycle that involves several discrete structural intermediates. These intermediates are characterized by discrete changes in the visible and the resonance Raman spectra of the chromophore (a retinal group linked to the protein by a Schiff base) and in the infrared spectrum of the protein itself. Protein structural changes are thought to change access to the protonated Schiff base via inward and outward facing aqueous channels, respectively, during different stages of the photocycle, thus allowing for vectorial proton movement across the cell membrane. A schematic model of the functional changes in structure that occur throughout the photocycle is given by the cartoon shown in Figure 1.We have recently begun electron diffraction studies on the intermediates in the bR photocycle, with the goal of using difference Fourier maps to see directly the structural changes that correspond to the previously observed spectroscopic changes.
Multiple isomorphous replacement for phase determination in protein crystals
Authors: Burmester Christoph , Holmes Kenneth C. , Schröder Rasmus R. 
Published: June 2020

Electron crystallography of 2D protein crystals can yield models with atomic resolution by taking Fourier amplitudes from electron diffraction and phase information from processed images. Imaging at atomic resolution is more difficult than the recording of corresponding high resolution electron diffraction patterns. Therefore attempts have been made to retrieve phase information from diffraction from heavy atom labelled protein crystals. The expected differences between native and labelled crystals are small, therefore a high experimental accuracy is necessary. This is achieved by the use of energy filter TEM and image plates, as dicussed in. Here we present electron diffraction data obtained from frozen hydrated 3D protein crystals with an energy filter microspcope and a specially designed image plate scanner. Data were recorded for the native crystal as well as for two different heavy atom derivatives. Differences between the native and the derivate forms can be detected and are significant.Electron diffraction patterns from frozen hydrated catalase crystals were recorded on an EFTEM Zeiss 912 Ω (120kV, zero loss mode, energy width ΔE=10eV, electron dose 5 e-/A2) using image plates and a quasi confocal scanner readout.
The effect of dates on the ultrastructure of hepatocytes of mice inoculated with Cerastes Cerastes venom
Authors: Al-Sallal A. , Amr Z. , Al-Bagdadi F. 
Published: June 2020

Upon fractionation of Cerastes Cerastes venom it was found to contain L-aminoacidoxidase, phosphodiesterase, hyaluronidase and phospholipase A. The pathological effects of snake venom on the kidney, muscle tissues, liver, spleen and lymph nodes5 were investigated. In this study we report the effects of dates on the ultrastructural morphology of hepatocytes of mice envenomized intraperitoneally with Cerastes Cerastes venom.The venom used in this study was collected from Cerastes Cerastes snake, which were usually found in Wadi Araba, south of Jordan. The extracted venom was lyophilized and kept at -20 degrees centigrade. Three white albino mice were starved for 60 hours and then fed dates. Then after twelve hours the mice were injected intraperitoneally with a lethal dose of Cerastes Cerastes. After 42 hours the mice were still alive. Control mice were not starved nor fed with dates,they were also envenomized intraperitoneally with lethal dose of Cerastes Cerastes venom, and the liver of all mice was dissected immediately after death.
Ultrastructural analysis of the physical interactions that occur between Baccillus SP. and polyurethane during biodegradation
Authors: Norton W.N. , Howard G. , Blake R. 
Published: June 2020

The scientific community is confronted with a number of significant environmental issues, including the dilemma of how to maintain, safely and effectively, the enormous quantity of organic and inorganic hazardous wastes that are produced in the U.S. alone. Substantial interest in the concept of bioremediation, the use of microorganisms to accelerate the degradation of environmental contaminants, has been generated during the past decade. Bacillus sp., has demonstrated an ability to degrade water dispersible polyurethane, a molecule normally exceedingly difficult for microbial organisms to metabolize. The primary objective of this investigation is to obtain basic ultrastructural information on the physical nature of polyurethane biodegradation conducted by Bacillus.A bacterial suspension of l×l09 cells was placed in one liter of a stock solution of polyurethane (3mg polyurethane/L distilled water). A comparable number of cells was maintained in 1 L of growth media and served as a control. At 2, 8, and 24 h subsequent to the initial exposure, samples were obtained from the experimental and control flasks and processed for phase-contrast microscopy, TEM and SEM.
High-resolution chemical mapping using tapping mode AFM with phase contrast
Authors: Chernoff Donald A. 
Published: June 2020

Introduction. A challenging problem in materials analysis is imaging the microstructure of composite surfaces. Some examples of composite surfaces are: contamination deposits, discontinuous (i.e. defective) thin films, devices built of composite materials, and cross-sectional specimens of composite materials. Techniques such as XPS and SIMS can provide detailed information about the chemical species present on the surface, but only average information is obtained for areas smaller than a few (μm wide. Auger can have sub-micron spatial resolution, but it provides little useful information about organic materials and it is difficult to use on insulating surfaces. In contrast, we have developed a new method for imaging chemical domains with spatial resolution of 10-20 nm. In principle, this method may be used on any surface.The TappingMode™ AFM1 uses an oscillating cantilever whose motion can be characterized by its amplitude and phase relative to its driver. In its most common mode of operation, this AFM uses the amplitude signal to sense the specimen surface, control the Z piezo and create a height image.
Modulated polarization microscopy displays the dynamics of cytoskeletal structures in living, motile cells
Authors: Kuhn J. R. , Poenie M. 
Published: June 2020

Cell shape and movement are controlled by elements of the cytoskeleton including actin filaments an microtubules. Unfortunately, it is difficult to visualize the cytoskeleton in living cells and hence follow it dynamics. Immunofluorescence and ultrastructural studies of fixed cells while providing clear images of the cytoskeleton, give only a static picture of this dynamic structure. Microinjection of fluorescently Is beled cytoskeletal proteins has proved useful as a way to follow some cytoskeletal events, but long terry studies are generally limited by the bleaching of fluorophores and presence of unassembled monomers.Polarization microscopy has the potential for visualizing the cytoskeleton. Although at present, it ha mainly been used for visualizing the mitotic spindle. Polarization microscopy is attractive in that it pro vides a way to selectively image structures such as cytoskeletal filaments that are birefringent. By combing ing standard polarization microscopy with video enhancement techniques it has been possible to image single filaments. In this case, however, filament intensity depends on the orientation of the polarizer and analyzer with respect to the specimen.
Ultrastructure of the basal cells of the uterine glands of mares infused with povidone iodine solution
Authors: Al-Bagdadi F. , Richardson G. , Eilts B. , McCoy D. , Braun W. , Archbald L. , Olsen L. , Thompson D. , Titkemeyer C. 
Published: June 2020

Gentamicin and povidone iodine infusion solutions have been used separately, to treat endometritis in mares. The effect of povidone iodine on the histology of the endometrium has been reported. This study describes the morphology of the fine structure of the endometrial epithelium and its response to povidone iodine infusion with the emphasis on the basal cell of the uterine gland.Ten light horse mares of breeding age were selected and divided into two groups. Five mares were used as controls and five mares were infused with 1 % povidone iodine solution. Estrous of the mares was controlled with two doses of prostaglandin, 11 days apart, so that all the mares were in the first 3 days of estrus at the beginning of the experimental period (day 0). Uterine biopsies were obtained on days 0, 3, 5, 7, 10, 15, 20, and 30 of the experimental period. The biopsies were obtained from the endometrium at the junction of the uterine body and the uterine horn using alternate sides for subsequent biopsies.
Calcitonin effects on myoblasts: an ultrastructural study
Authors: González Santander R. , Toledo Lobo M.V. , Martínez Alonso F.J. , Martínez Cuadrado G. , González-Santander Martínez M. , Monteagudo M. 
Published: June 2020

Several studies have provided detailed descriptions about the effects of calcitonin (CT) on different cell types such as osteoclasts, multinucleate giant cells and trophoblastic cells. CT main role is associated with the maintenance of peripheral Ca2+homeostasis and it may also modulate free intracellular Ca2+. Myoblasts are particularly sensitive to changes in extra and intracellular Ca2+concentration, so we have studied CT effects on myotome myoblasts differentiation.Chick embryos from 56-59 h. of incubation (Hamburger and Hamilton stages 16-17) were injected with 0,25 IU of CT dissolved in 125 ul of 0,9 % sterile saline solution (CALSYNAR-50, from Rorer Labs.- synthetic lyophilized salmon CT made by Armour Pharmaceutical Co., Kankakee, Illinois, USA). CT was injected into the ammniotic cavity through a window in the egg shell. Afterwards, the window was closed and the eggs returned into the incubator, until embryos had incubated for 103 h., to reach H.H. stage 24. Some embryos were only injected with saline solution (controls).
Wheat necrosis induced by Pyrenophora tritici-repentis toxin
Authors: Freeman Thomas , Rasmussen Jack , Francl Leonard , Meinhardt Steve 
Published: June 2020

Tan spot is a serious foliar disease of wheat caused by Pyrenophora tritici-repentis. This fungal pathogen produces a proteinaceous phytotoxin that induces necrosis in susceptible but not resistant cultivars. Larez et al. reported generalized membrane breakdown and cell death in advance of fungal spread, an effect presumably due to excreted fungal products, including the necrosis toxin. The direct ultrastructural effects of necrosis toxin isolated from P. tritici-repentis have not been previously examined.Crude extract from a culture of isolate 86-124 (1) was thawed and centrifuged for 20 min at 35O00g. The supernatant was filtered through a 0.45 μm Whatman nylon filter and placed in dialysis tubing with a 3,500 molecular weight cut off. The crude extract was dialyzed overnight against 10 volumes of 20 mM sodium acetate buffer, pH 4.8. The dialyzed extract was loaded onto a fresh 10 ml S-sepharose Fast Flow column (Pharmacia) previously equilibrated with 20 mM sodium acetate.
The removal and morphology of intact biofilms from implanted venous access devices
Authors: Gregory M.A. , Hadley G.P. 
Published: June 2020

The insertion of implanted venous access systems for children undergoing prolonged courses of chemotherapy has become a common procedure in pediatric surgical oncology. While not permanently implanted, the devices are expected to remain functional until cure of the primary disease is assured. Despite careful patient selection and standardised insertion and access techniques, some devices fail. The most commonly encountered problems are colonisation of the device with bacteria and catheter occlusion. Both of these difficulties relate to the development of a biofilm within the port and catheter. The morphology and evolution of biofilms in indwelling vascular catheters is the subject of ongoing investigation. To date, however, such investigations have been confined to the examination of fragments of biofilm scraped or sonicated from sections of catheter. This report describes a novel method for the extraction of intact biofilms from indwelling catheters.15 children with Wilm’s tumour and who had received venous implants were studied. Catheters were removed because of infection (n=6) or electively at the end of chemotherapy.
Immunohistochemical localization of prolactin receptor in human digestive tissues
Authors: García-Caballero T. , Gallego R. , Fraga M. , Pintos E. , Beiras A. 
Published: June 2020

Prolactin (PRL) is primarily recognized for its lactogenic effect. However, it is known that this polypeptide hormone exerts a great variety of biological functions acting on reproduction, osmoregulation, growth, metabolism, immunomodulation and even on behavior. The actions of PRL initiate with hormone binding to a specific cell surface receptor that belongs to the cytokine/GH/PRL receptor family or the hematopoietin receptor family The PRLR is widely distributed in numerous tissues. The aim of the present work was to investigate by immunohistochemistry the cellular distribution of PRLR in the human gastrointestinal tract and associated glands (liver and pancreas).Samples of normal esophagus, stomach, small and large intestine, liver and pancreas were obtained from surgical pieces or recent autopsies. These samples were immersion-fixed in 10% buffered formalin for 24 hr, dehydrated and embedded in paraffin routinely. B6.2 anti-PRLR and avidin-biotin-peroxidase complex (ABC) procedure were employed. The B6.2 mouse monoclonal antibody (prepared against a membrane enriched fraction of human metastatic breast cancer), was generously provided by Dr. Barbara K. Vonderhaar and used at a dilution of 1:250, for 1 hr.
Sequential staining and de-staining of a single section by a panel of fluorescently-tagged lectins
Authors: Michael Stanley C. , Phillips Thomas E. 
Published: June 2020

Numerous previous studies have used fluorescently tagged lectins to demonstrate the mucin glycoprotein secretory product of intestinal goblet cells are heterogeneous in respect to their lectin binding sites . Lectins stain the mucin secretory product in partially overlapping subpopulations of goblet cells. There are several difficulties in using a panel of fluorescently tagged lectins to determine the overlapping sites of binding. First, steric hindrances resulting from the binding of the first lectin compete with the subsequent binding of other lectins to the same or adjacent sites. Secondly, the number of fluorescent tags that can be practically differentiated by routinely configured microscopes is generally limited to two or three. As an alternative approach, we investigated whether 8 M urea could remove previous bound lectins without damaging the carbohydrate binding sites. Microwave treatment with 8 M urea has previously been used to recover antibody binding sites masked by fixation and embedding.Small pieces of distal colon were removed from anesthetized rats and fixed for 2 hours at room temperature in 2% freshly-depolymerized paraformaldehyde in 70 mM NaCl, 30 mM HEPES, 2 mM CaCl2, pH 7.4.
An improved cryofixation technique for optimal orientation of Caenorhabditis elegans for cryosectioning and EPXMA
Authors: Roberts Edward , Wallace Nancy , Freedman Jonathan , LeFurgey Ann 
Published: June 2020

INTRODUCTION: Plunge freezing into liquid cryogens has been frequently employed with success for cryofixation of biological specimens <lmm in size; however, positioning of cells or organisms with a precise orientation for subsequent cryosectioning is difficult. In these studies, a metal mirror cryofixation device, e.g. cryogun, has been tested to determine its applicability for cryofixation of small organisms such as nematodes or larval invertebrates with specific positioning. The objective of the experiments was to determine the optimum technique for rapid cryofixation and cryosectioning of the intestinal tract and lumen of the nematode Caenorhabditis elegans, prior to electron probe x-ray microanalysis (EPXMA) of subcellular elemental distribution.METHODS: Freezing and sectioning quality obtained using plunge freezing into -190°C liquid propane (Figure la) was compared with that obtained with -196°C metal mirror fixation using the cryogun (PS 1000, Delaware Diamond Knives, Wilmington, DE)(Figure lb). C. elegans were grown in culture to the adult stage, and individual nematodes were placed on either (1) a wooden specimen stub compatible with the plunge freezing device (Figure 2a) or (2) a cryogun specimen mount (Figure 2b).
Advantages of Low Temperature SEM for Bacterial Studies
Authors: Roy Stéphane , Babic Isabelle , Watada Alley E. , Wergin William P. 
Published: June 2020

The application of transmission electron microscopy (TEM) has greatly increased our understanding of structure-function relationships in bacteriology. However, to achieve further advancements investigators are seeking preparation procedures that would avoid the artifacts associated with conventional chemical fixation, dehydration and critical point drying or embedding. In our laboratory a field emission scanning electron microscope (SEM) was recently equipped with a cold stage. This combination of techniques, referred to as low temperature (LT) SEM, allowed us to examine frozen, fully hydrated biological specimens. The present investigation images bacteria that were cryofixed for LTSEM observations and then freeze-substituted for TEM observations. In addition an attempt was made to culture the samples that had been cryofixed and observed with LTSEM so that taxonomic identification and further microscopic observations could be made.Bacteria used in this study were isolated from spinach leaves (variety New Jersey). LTSEM observations of cryofixed samples were performed on a Hitachi S-4100 field emission SEM equipped with an Oxford CT-1500HF Cryotrans System.
Ionic channels for mechanoelectrical transduction and frequency tuning by vertebrate hair cells
Authors: Hudspeth A. J. 
Published: June 2020

The electrical activity of vertebrate hair cells, including mechanoelectrical transduction, resonant frequency tuning, and synaptic transmission, results from the action of an ensemble of ionic channels. In an effort to understand how hair cells function as the sensory receptors of the internal ear, our research group is conducting in vitro investigations of the ionic channels of saccular hair cells from the bullfrog, Rana catesbeiana.Mechanoelectrical transduction commences when stimuli, derived from sounds or accelerations, deflect the hair bundle, a cluster of enlarged microvilli termed stereocilia.
The ultrastructure of hepatocellular carcinomas in english sole (Parophrys vetulus) from puget sound
Authors: Stehr Carla 
Published: June 2020

High prevalences of liver neoplasms have been found in English sole (Parophrys vetulus) from urban waterways of Puget Sound, Washington. Although the etiology of these neoplasms is not known, evidence suggests that chemical contaminants may be the causative agents. Electron microscopy studies were undertaken to investigate subcellular structures of hepatocellular carcinomas from these fish.English sole were collected by otter trawl from several urban waterways of Puget Sound, Washington State. Grossly visible liver nodules were excised from freshly killed fish and divided for light and electron microscopy. Tissues for light microscopy were processed by standard histological procedures, and stained with Hematoyxlin and Eosin.
Sequential degranulation of eosinophils induced by antigen or autocoids in allergic humans
Authors: Sjoerdsma Kate W. , Metzger W. James 
Published: June 2020

Eosinophils are important to the pathogenesis of allergic asthma, and are increased in bronchoalveolar lavage within four hours after bronchoprovocation of allergic asthmatic patients, and remain significantly increased up to 24 hours later. While the components of human eosinophil granules have been recently isolated and purified, the mechanisms of degranulation have yet to be elucidated.We obtained blood from two volunteers who had a history of allergic rhinitis and asthma and a positive skin test (5x5mm wheal) to Alternaria and Ragweed. Eosinophils were obtained using a modification of the method described by Roberts and Gallin.
Investigation of shock-wave deformation history from recovered structure
Authors: Mogilevsky M.A. , Bushnev L.S. 
Published: June 2020

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.
Tem studies of partially crystallized Y-Si-Al-O-N glasses
Authors: Rai R.S. , Dinger T.R. , Thomas G. 
Published: June 2020

Although Si3N4 has many attractive refractory properties some limitations occur due to intergranular oxynitride glass phases that result from liquid phase sintering with oxide additions. Hence it is of fundamental and technical importance that a more detailed understanding of such glasses and possible crystallization behavior is obtained.This research is being done on a series of compositions of Y-Si-Al-O-N which can be made as glasses and subsequently heat treated to promote crystallization. Here the results of crystallization (of glass Y.26Si.30Al.11ON.11) leading to Y2Si2O7 crystals of different forms is described. Specimens for electron microscopic observations were prepared by ion milling followed by a thin layer of carbon and examined by conventional TEM, CBED, EDXS and at atomic resolution in the Berkeley ARM.
Recrystallization behavior of ion beam modified α-Al2O3
Authors: Sklad P. S. 
Published: June 2020

The importance of Al2O3 as a technological material is demonstrated by its use in such widely varying fields as energy production and conversion, catalysis, primary metal production, and communications. Properties of interest include room temperature and elevated temperature strength and fracture toughness, hardness and wear resistance, chemical stability in aggressive environments, high surface area and thermal stability, adhesion of thin metallic films, and dimensional stability. Many of the properties of critical interest are surface controlled.Until recently charged particle techniques have been used primarily to investigate the radiation damage behavior of Al2O3. However, in the last few years ion beam techniques have been used extensively as a means to modify the near-surface properties of Al2O3. One aspect of this work involves the use of ion implantation to produce an amorphous phase on a single crystal α-Al2O3 substrate and the investigation of the recrystallization behavior during post implantation annealing.