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PubMed1980

Total rate imaging with x-rays (TRIX)--a simple method of forming a non-projection x-ray image in the SEM using an energy dispersive detector and its application to biological specimens.

X-ray images can be formed in a conventional scanning electron microscope equipped with a Si(Li) energy dispersive spectrometer. All the x-ray events generated in the electron beam scanning process are synchronously displayed in the same manner as for dot maps. The quasi-digital image formed using Total Rate Imaging with X-rays (TRIX) exhibits good gray scale contrast and is dependent on topography, orientation and atomic number. Although this latter dependence is complex, it has been found useful in locating several types of inclusions in lung tissue (silicosis), human alveolar macrophages and cigarette smoke condensate. This is because of the greater depth of penetration of x-rays than backscattered electrons (BSE) usually used for such localizations in a matrix, and the negligible sensitivity of the Si(Li) detector to x-rays from an organic biological matrix. The optimum procedure is to use a combination of TRIX and BSE to investigate such specimens.

Electron Probe Microanalysis↗
PubMed1995

Mineral element analysis of carious and sound rat dentin by electron probe microanalyzer combined with back-scattered electron image.

We recently demonstrated the advantages of back-scattered electron images (COMPO) in the visualization of dentinal caries, and the relationship of the change in the dentin fluorescence pattern in caries lesions. However, the exact nature of these changes is not known. In this paper, the nature of the changes in the areas with reduced mineral content in COMPO images was investigated. We examined the relation of changes in mineral elements and the appearance of soft carious and sound dentin in COMPO images using a scanning electron microscope (SEM) equipped with an electron probe microanalyzer (EPMA). Rat molars with small dentinal caries lesions just under the DEJ were chosen for the study. The Ca, P, Na, Mg, Zn, F, and total contents were determined by EPMA from five different dentin sites, and the Ca/P and Mg/Ca ratios were calculated. Generally, the lowest contents were found in caries lesions and highest in mantle dentin, with the exceptions of Mg and Zn. The Ca/P ratio was lowest in mantle dentin and highest in carious dentin. The results confirm that the change in fluorescence in the dentinal caries lesion is correlated with the very initial changes in mineral content, and that EPMA used in combination with COMPO images is a useful tool for determining small changes in mineral elements in the carious and adjacent areas of dentin.

Animals↗
PubMed2000

Imaging the effects of individual zinc impurity atoms on superconductivity in Bi2Sr2CaCu2O8+delta

Although the crystal structures of the copper oxide high-temperature superconductors are complex and diverse, they all contain some crystal planes consisting of only copper and oxygen atoms in a square lattice: superconductivity is believed to originate from strongly interacting electrons in these CuO2 planes. Substituting a single impurity atom for a copper atom strongly perturbs the surrounding electronic environment and can therefore be used to probe high-temperature superconductivity at the atomic scale. This has provided the motivation for several experimental and theoretical studies. Scanning tunnelling microscopy (STM) is an ideal technique for the study of such effects at the atomic scale, as it has been used very successfully to probe individual impurity atoms in several other systems. Here we use STM to investigate the effects of individual zinc impurity atoms in the high-temperature superconductor Bi2Sr2CaCu2O8+delta. We find intense quasiparticle scattering resonances at the Zn sites, coincident with strong suppression of superconductivity within approximately 15 A of the scattering sites. Imaging of the spatial dependence of the quasiparticle density of states in the vicinity of the impurity atoms reveals the long-sought four-fold symmetric quasiparticle 'cloud' aligned with the nodes of the d-wave superconducting gap which is believed to characterize superconductivity in these materials.

Journal Article↗
PubMed2000

Use of a Technovit 7200 VLC to facilitate integrated determination of aluminum by light and electron microscopy.

Technovit 7200 VLC is an excellent embedding medium for both inorganic histochemistry by light microscopy and X-ray microanalysis by scanning and transmission electron microscopy. Liver samples from rats after intraperitoneal treatment with aluminum chloride were fixed in glutaraldehyde and embedded in the resin. Thick sections were easily cut on an ultramicrotome and stained with aluminon for aluminum (Al). An intense positive reaction with aluminon was observed in the Kupffer cells by light microscopy. The surface structures of the same resin block cut for light microscopy were observed under a scanning electron microscope fitted with an energy dispersive X-ray spectrometer. The Kupffer cells appeared white in the backscattered mode. Localization of Al in the Kupffer cells was confirmed by an X-ray distribution map in the scanning electron microscope. Subcellular localization of Al in the Kupffer cells was performed on the same semithin sections using a transmission electron microscope equipped with an energy dispersive X-ray spectrometer. Most Al was found in lysosomes of the Kupffer cells. The resin was stable in the electron beam and chlorine-free.

Acrylic Resins↗
PubMed2000

The friction and wear patterns of orthodontic brackets and archwires in the dry state.

Frictional resistance at the bracket-archwire interface has been demonstrated to impede tooth movement when sliding mechanics are used. Thus, the coefficients of friction of titanium and stainless steel brackets used in conjunction with stainless and ion-implanted beta-titanium archwires were investigated using a single contact interface between the brackets and archwires. The wear patterns between the brackets and the.016- in flat archwire surfaces were also examined using scanning electron microscopy and energy dispersive x-ray analysis. Stainless steel brackets tested with. 016-in flat stainless steel wire surfaces recorded the lowest coefficient of static friction mean (0.289), whereas titanium brackets paired with.016-in flat ion-implanted beta-titanium wire surfaces produced the highest mean (0.767). Stainless steel brackets had significantly (P <.05) lower coefficients of friction than titanium brackets for all wires except.020-in round stainless steel wires. Ion-implanted beta-titanium wires generally had significantly larger coefficients of friction than stainless steel wires. The increased friction of the titanium and ion-implanted beta-titanium alloys is also reflected in the severity of their wear patterns. An inverse relationship between friction and archwire surface dimension was generally found for ion-implanted beta-titanium wires. Round stainless steel wires demonstrated lower coefficients of kinetic friction than the flat stainless steel wire surfaces.

Analysis of Variance↗
PubMed1982

Scanning electron microscopy and EDX analysis of exocrine and endocrine gland cells of rat pancreas surface-etched in an oxygen plasma.

Pancreas, double-fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin was cut into sections 0.5-1 micron thick. The sections were surface-etched in an oxygen plasma produced by exciting oxygen with a radio frequency generator. Structural components of exocrine and endocrine cells were morphologically investigated in the secondary electron image mode of the SEM. Moreover, in order to identify some cell components such as endocrine granules, the morphological image obtained of the etched surface by the SEM were compared with those seen in a TEM, using the serial sections from the same tissue block and at the same cellular level. For a microanalytical investigation, tissues were fixed with glutaraldehyde alone. The structural components of exocrine and endocrine cells were analyzed by SEM/EDX. A better resolution under the SEM was obtained of 0.5-0.8 micron thick sections after surface-etching in an oxygen plasma for 1 minute. Intracellular structures such as nuclear membranes, nucleolus, mitochondria, rough endoplasmic reticulum and zymogen granules were readily identifiable. Moreover, the internal structure of organelles such as cristae of mitochondria was recognized. In the serial sections, the mode of arrangement of intracellular structures in the SEM was well consistent with those in the TEM. The peaks of phosphorus, sulphur and calcium were clearly detected from the intracellular components such as nucleolus, nuclear membranes and secretory granules.

Animals↗
PubMed1995

[Morphological changes on gold-coated brass endodontic pins].

Scanning electron microscope (SEM) connected with X-ray microanalysis (EDX) was used to study surface alterations of gold-coated brass dental pins (Dentatus), taken out after some years from restored teeth due to necessity for repeating a restorative therapy. The study method led to establish that: --the gold coating of the base material, constituted of copper alloy, absolutely insufficient to prevent corrosion attack; --the observed morphological alterations are the consequence of a localized corrosion attack, produced by anaerobic bacteria, which origin is confirmed by the presence of S on the most attacked points; --finally the corrosive phenomenon does not cause a periapical pathology, but the process is contrary, or rather, it is the pathology that leads to the favourable conditions to create corrosion.

Copper↗
PubMed1995

Conjunctival tissue examination in severe eye burns: a study with scanning electron microscopy and energy-dispersive X-ray analysis.

BACKGROUND: Long-lasting inflammation is a major problem in treatment after severe eye burns and may find expression in an altered elemental composition of the conjunctiva. Particulate contamination of biological tissue induces such inflammatory processes. In the anterior eye segment, trauma or subsequent therapy may give rise to such contamination. Scanning electron microscopy and energy-dispersive X-ray analysis are able to detect traumatic residues of submicron size and changes of the elemental composition. METHODS: Conjunctival specimens from first-time peridectomy of three healthy and nine severely burnt-eyes were examined with scanning electron microscopy and energy-dispersive X-ray analysis. The samples were prepared as cryo- or paraffin sections, mounted on carbon blocks and coated with evaporated elemental carbon. RESULTS: The samples of healthy conjunctiva showed higher concentrations of Na, P and CI. These elements showed lower concentrations in conjunctival stroma of burnt eyes excised before the 20th day after trauma than in material obtained subsequently. In two burnt conjunctival specimens there was severe traumatic contamination with Ca in Ca(OH)2 and CaO burns, and in one case the traumatic substance was Si, in a peroxide plus silicone spray burn. In the remaining six cases, particulate contamination with Fe, Al, Ni, Zn, Cu, Ti and other substances was present in the burnt conjunctivas, while no contamination was detected in the specimens of healthy conjunctivas. CONCLUSIONS: The origin of the contaminant particles is assumed to be the trauma itself and the subsequent therapy. These investigations stress the importance, for clinical purposes, or early peridectomy and contamination-free therapy.

Burns, Chemical↗
PubMed1995

Characterization of thin hydroxyapatite layers formed on anodic titanium oxide films containing Ca and P by hydrothermal treatment.

An anodic titanium oxide film containing Ca and P (AOFCP) was formed on commercially pure titanium which was anodized in an electrolytic solution of dissolved beta-glycerophosphate (beta-GP) and calcium acetate (CA). Hydroxyapatite (HA) crystals were precipitated by hydrothermally heating the AOFCP at 300 degrees C. After hydrothermal treatment, the film was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray microanalysis (EDX), and tensile tests. The morphology, composition, and amount of HA crystals precipitated were significantly affected by the composition of the electrolytes. Near-stoichiometric HA crystals with high crystallinity were precipitated completely covering the AOFCP surface at specific electrolyte concentrations. The HA layers were thin at 1-2 microns in thickness. The adhesive strength of the film increased with decreasing electrolyte concentration and the maximum value was about 40 MPa. In vitro tests for 300 days suggested that the stability of the film was high. The high adhesive strength may result from the AOFCP existing as an intermediate layer between the HA layer and a titanium substrate. The intervention of the AOFCP may have prevented abrupt changes in Ca and P content at an HA coating-titanium interface as seen in a plasma-sprayed one. The porous TiO2 matrix of the AOFCP may be suitable for nucleation sites of HA crystals, as well as SiO2 matrix of silicate bioactive glasses or glass ceramics.

Acetates↗
PubMedDate not supplied

A quantitative cryo-scanning X-ray microanalysis protocol for the examination of the eye.

Analysis of elements present in fluids contained in small, poorly accessible sections of biological tissue is challenging. The choroid of the eye, which is a vascular tissue approximately 100 microm thick, surrounds the retina for the purposes of nutrient supply and metabolite removal, and which in the chick shows dramatic volumetric change in response to visual experiences. Because fluid homeostasis is critical to good vision, a complete understanding of the ionic changes driving large shifts in ocular fluids is required. However, the structure of the choroid and retina make extraction of pure fluids for analysis extremely difficult. Elemental x-ray analysis on a transverse chorioretinal specimen was performed after rapid freezing of a whole chick eye in liquid nitrogen, and mechanically fracturing the frozen globe. Using a Polaron Cryotrans System on a Cambridge S-360 scanning electron microscope and a Kevex Quantum detector, spectra were obtained for blood vessels, lymphatic vessels and vitreous that were readily visible at 265x. Analysis was performed on a frozen control solution of the elements found in the vessels. The elements and their concentrations found in blood vessels by x-ray analysis compared well with those from whole blood as established by conventional means. The analysis for lymph yielded results compatible with expectations; no other published data for small lymphatics enable a direct comparison. In conclusion, x-ray analysis can be used to acquire information that is otherwise unobtainable from tissue in situ. The same bulk-frozen elemental microanalysis protocol would have application to other organs and tissues when access to the site would destroy the integrity of the tissue under investigation.

Animals↗
PubMed1996

Biopersistence of man-made vitreous fibers and crocidolite asbestos in the rat lung following inhalation.

This study investigated possible relationships between fiber bio-persistence in the lung and previously observed differences in pulmonary toxicity between asbestos and man-made vitreous fibers (MMVF) following inhalation exposure. Fischer 344/N rats were exposed nose only, 6 hr/day for 5 days to 30 mg/m3 MMVF (two fiberglass compositions, rock wool, or slag wool) or to 10 mg/m3 crocidolite asbestos. At eight time points up to 1 year postexposure, lung fiber burdens were analyzed for number/lung and bivariate dimensions using scanning electron microscopy (SEM) and for chemical composition using SEM energy dispersive spectroscopy. After 365 days, > 95% of long (> 20 microns) MMVFs had disappeared from the lung compared to only 17% of long crocidolite fibers. Longer MMVFs disappeared more rapidly than short MMVFs, suggesting that long fibers were dissolving or breaking. Mean diameters and lengths of the MMVFs decreased with time, while the mean diameter of crocidolite remained unchanged and its mean length showed an apparent increase, probably related to macrophage-mediated clearance of short fibers. Leaching of oxides occurred in the fibrous glasses and slag wool and correlated with morphological changes in the fibers over time. No chemical or morphological changes were observed in crocidolite fibers. These changes in MMVF number, chemistry, and morphology over time in lung tissue compared to crocidolite asbestos demonstrate the relatively low biological persistence of some MMVFs in the lung and may explain why these MMVFs are not tumorigenic in rats, even after chronic exposure at high concentrations.

Administration, Inhalation↗
PubMedDate not supplied

Oxidized titanium screws coated with calcium ions and their performance in rabbit bone.

PURPOSE: The aim was to answer a fundamental question: Do the chemical properties of titanium implants influence osseointegration? MATERIALS AND METHODS: Screw-type implants produced of turned commercially pure (grade 1) titanium (controls) and electrochemically calcium-deposited titanium implants (Ca test implants) were placed in the tibiae and femora of a total of 10 mature New Zealand white rabbits. The macro arc oxidation method was applied for Ca implants. Surface oxides were characterized with different analytic techniques, including x-ray photoelectron spectroscopy, auger electron spectroscopy, scanning electron microscopy, thin-film x-ray diffractometry, and TopScan 3D. The bone response was evaluated by biomechanical tests, histology, and histomorphometry. RESULTS: After a follow-up period of 6 weeks, test Ca implants showed a significant increase in mean peak removal torque (P = .0001) and in the histomorphometric measurement of bone-to-metal contact around the implants (P = .028) in comparison to controls. In addition, more mature mineralized bone was observed adjacent to test Ca implants compared to controls, as evaluated on 10-microm undecalcified, toluidine blue-stained, cut, and ground sections. DISCUSSION: The potential role of surface Ca chemistry to a superior bone response is discussed with specific reference to interaction with Ca(+)-binding proteins and function as binding sites of calcium phosphate mineral. CONCLUSION: The present results suggest that the surface chemical composition of titanium implants is of great importance for the bone response. Ca ion-deposited titanium implants showed fast and strong osseointegration in the rabbit bone model.

Animals↗
PubMed1998

Blood vessels and red blood cells preserved in dinosaur bones.

Dinosaur bones, 80 million years old, were studied in the scanning electron microscope, and subjected to X-ray microanalysis. Samples for the investigations were prepared according to specially elaborated, and simultaneously described methods. Analysed were (a) the morphological structure of the blood vessels and (b) the remains of their contents. The walls of the blood vessels were found to be morphologically identical with those in present-day reptiles. Bodies were found at several places inside the vessels which strongly remind one of erythrocytes in modern bones. X-ray microanalysis of places where these bodies were accumulated revealed much higher levels of iron, than at any other regions of the blood-vessel wall. Further analysis of the "dinosaur erythrocyte" iron content could be a starting point for the possible determination of oxygen in the earth's atmosphere, 80 million years ago.

Animals↗
PubMed1979

Ultrastructure and x-ray microanalysis of macrophages exposed to cadmium chloride.

Macrophages have a direct role in the inflammatory response to cadmium exposure. Cadmium is not only an important air pollutant, but is also one component of cigarette smoke. To study the effects of soluble cadmium on macrophages, two model systems were chosen:rabbit alveolar macrophages (RAMs) obtained by pulmonary lavage and peritoneal macrophages elicited by intraperitoneal injections of 10(7) viable M. bovis, bacillus Calmette Guérin (BCG MACs). Macrophages were maintained in standard tissue culture medium from 4 to 30 hours with concentrations of cadmium chloride (CdCl2) ranging from 0 to 1.0 mM. Attached macrophages and RAMs in suspension were studied by conventional transmission electron microscopy (TEM), scanning electron microscopy (SEM), and energy dispersive x-ray microanalysis (EDX). In addition to routine techniques for TEM and SEM, preparatory procedures included snap freezing in liquid propane, and either cryoultramicrotomy or freeze-substitution with 1% osmium tetroxide in acetone. By TEM many macrophages exhibited laminated nuclear inclusions at doses as low as 0.05 mM CdCl2) (at 20 hrs) and as early as 4 hrs (at 1.0 mM CdCl2). Sections of cells fixed by freezing exhibited the same nuclear inclusions as well as mitochondrial densities that were not visible with any other preparative technique. Cadmium was demonstrated in the nuclear inclusions and mitochondrial densities by EDX in snap frozen cells. Lesser amounts of cadmium were also detected diffusely in treated cell cytoplasm and nuclei. Cadmium was only detected by EDX in cells fixed by freezing. These studies document the localization of Cd in nuclear inclusions and mitochondria providing morphological support for the biochemical findings of other laboratories. In addition, the value of fixation by freezing over conventional chemical fixation is illustrated.

Animals↗
PubMed2000

Effect of a ceramic and a non-ceramic hydroxyapatite on cell growth and procollagen synthesis of cultured human gingival fibroblasts.

BACKGROUND: Ceramic hydroxyapatites and non-ceramic hydroxyapatites have been used extensively as alloplastic materials for bone reconstruction. However, different forms of hydroxyapatite induce different types of tissue response. METHODS: Human gingival fibroblasts (FMM1 cells) were used to analyze ceramic and non-ceramic hydroxyapatite biocompatibility. The cells were grown on surfaces covered either by collagen (control group), collagen plus ceramic hydroxyapatite, or collagen plus non-ceramic hydroxyapatite. Scanning electron microscopy, growth and cell viability curves, and procollagen immunoprecipitation were obtained. For the growth and viability curves, 10(4) cells were seeded on 60 mm dishes. Cells from each group were counted, in triplicate, at 1, 3, 4, 5, and 6 days after seeding using the Trypan blue dye exclusion assay. RESULTS: The cells grew in close contact with both types of hydroxyapatite particles. No differences were found in the amount of procollagen synthesis among any experimental group. The cultures treated with ceramic hydroxyapatite had a growth delay for the first 5 days. There was no difference in cell viability between the control group and the non-ceramic hydroxyapatite group. However, cultures treated with ceramic hydroxyapatite showed significantly lower viability percentages than the other groups. CONCLUSIONS: Hydroxyapatite supports cell growth and fibroblast metabolism including collagen production, and hence is biocompatible. Cell viability and structural studies showed that non-ceramic hydroxyapatite has relevant physical and biological properties as an implant material.

Algorithms↗
PubMed1987

Silver enhancement of lectin-gold and enzyme-gold cytochemical labelling of eggs of the nematode Onchocerca gibsoni.

Wheat germ agglutinin-gold and chitinase-gold complexes were used to demonstrate the presence of chitin on the surfaces of eggs of the animal parasitic nematode Onchocerca gibsoni. The gold complexes were enhanced by silver intensification and examined by light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Distinctive labelling of the egg surfaces was obtained with both probes in all three microscope modes. The results indicate that the small colloidal gold markers (3-10 nm) commonly used for high resolution TEM studies may be silver enhanced and also used for sensitive LM and SEM studies.

Animals↗
PubMed1995

Energy-dispersive X-ray microanalysis of calcified tissues after NaOCl treatment and/or resin embedding.

By energy-dispersive X-ray microanalysis (EDX) in scanning electron microscopy, we studied the calcification of the inner-basic lamellas of a cow bone and the coronal cementum of a horse tooth treated with sodium hypochlorite (NaOCl). These tissues were divided into 4 groups with a combination of NaOCl treatment and polyester-resin embedding including, [A]: non-NaOCl + Resin, [B]: non-NaOCl + non-resin, [C]: NaOCl + Resin, and [D]: NaOCl + non-Resin. From the Ca and P values by EDX analysis, it was suggested that the natural porous spaces of [B] were higher than those of [A], and both the natural and NaOCl-soluble porous spaces were highest in [D]. However, [A] had the lowest porous spaces in both the tissues because the micropores formed 3-dimensionally by NaOCl treatment might be incompletely filled with the resin. The backscattered electron microscopy and the difference of the Ca/P ratios indicated that the NaOCl treatment of the calcified tissues caused some minerals besides organic materials to dissolve. Thus, the sample preparation of [B] is suitable for the quantitative EDX of calcified tissues, whereas the data of [C] except for the Ca/P ratio may be used to approximate the Ca and P contents.

Animals↗
PubMed1997

Changes in surface levels of mercury, silver, tin, and copper of dental amalgam treated with carbamide peroxide and hydrogen peroxide in vitro.

OBJECTIVES: The effect of 10% carbamide peroxide or 10% hydrogen peroxide on the surface levels of mercury, silver, tin, and copper of amalgam fillings was tested in vitro with scanning electron microscopy and energy dispersive spectrometric microanalysis. STUDY DESIGN: Samples of amalgam were treated for 14 and 28 days with either 10% carbamide peroxide or 10% hydrogen peroxide solutions and compared with phosphate buffer controls. RESULTS: A significant increase in mercury levels occurred after treatment with carbamide peroxide for 14 days (p < 0.01) and 28 days (p < 0.001) and after treatment with hydrogen peroxide for 28 days (p < 0.001). A significant increase in silver levels occurred after treatment with carbamide peroxide for 14 days (p < 0.05) and 28 days (p < 0.01) and subsequent to treatment with hydrogen peroxide for 14 days (p < 0.05) and 28 days (p < 0.001). A significant reduction in tin levels occurred after treatment with hydrogen peroxide for 14 days (p < 0.01) and 28 days (p < 0.001), and after treatment with carbamide peroxide for 28 days (p < 0.01). A significant reduction in copper levels was found after treatment with carbamide peroxide for 14 days (p < 0.05). CONCLUSIONS: It appears that prolonged treatment with bleaching agents may cause microstructural changes in amalgam surfaces, possibly increasing exposure of patients to toxic byproducts.

Carbamide Peroxide↗