[Scanning electron microscopy (SEM) and x-ray microanalysis of enamel during the transitional post-secretory phase of ameloblasts].
Explore the source record for details and available documents.
Ameloblasts↗
SEARCH · Search PubMed
Results for “Electron Probe Microanalysis”
Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Microanalysis with a soft X ray scanning microprobe.
Explore the source record for details and available documents.
Bone Diseases↗
X-ray microanalysis of epon sections after oxygen plasma microincineration.
Dark-gold sections of osmium tetroxide-fixed, Epon-embedded brown adipose tissue before and after low-temperature oxygen plasma microincineration were examined using a high-resolution scanning transmission electron microscope and an energy-dispersive X-ray spectrometer. Microincineration produced ash patterns which were free of organic matrix, chlorine (from the Epon) and probably osmium (from the fixative). X-ray sensitivity was improved by a factor of 2-4 owing to decreased background, and sulphur, calcium and probably phosphorus were detected in the ash. Fidelity of the ash patterns permitted microanalytical spatial resolution of 0.1 micrometer or better. Oxygen plasma microincineration is thus shown to offer advantages for high resolution X-ray microanalysis of conventionally sectioned biological material. Its future application to shock-frozen, frozen-dried, unstained sections is indicated.
Adipose Tissue, Brown↗
Electron probe X-ray microanalysis of the effects of Bacillus thuringiensis var kurstaki crystal protein insecticide on ions in an electrogenic K+-transporting epithelium of the larval midgut in the lepidopteran, Manduca sexta, in vitro.
An alkaline hydrolysate of Bacillus thuringiensis var kurstaki HD1 (Btk) parasporal crystals was administered at 25 micrograms ml-1 (f.c.) to isolated, short-circuited, midguts of tobacco hornworm (Manduca sexta) larvae. The short-circuit current (s.c.c.), a precise measure of K+ active transport, was inhibited by 78% in 10 min in Btk-treated midguts as compared to controls. The elemental concentrations of K, together with Na, Mg, P, S, Cl and Ca, as well as the water content, were determined by electron probe X-ray microanalysis (EPXMA) in the muscle cells, columnar cells and goblet cells, as well as in the extracellular goblet cavity and the bathing media. The average K concentration in the goblet cell cavity was 129 mmol/kg wet wt in control midguts but only 37 mmol/kg wet wt in Btk-treated midguts. The elemental concentrations, including that of K, in other cell compartments were much less affected by Btk, but a rise in total cell calcium is suggested. It has been previously suggested that in vitro Btk acts specifically on limited regions of the apical membrane of the midgut epithelial cells. The simplest interpretation of the EPXMA results would be that initially Btk interacts specifically with the goblet cell apical membrane, which bounds the goblet cavity and contains the K+ pump responsible for the s.c.c. and high transepithelial potential difference (p.d.). Such interaction results in a rapid disruption of K+ transport across the goblet cell apical membrane, leading to dissipation of the K+ gradient and loss of p.d. The histopathological changes previously reported by other workers would then be a consequence of K+ pump inhibition causing changes in the intracellular pH, Ca2+ etc. Some possible molecular bases for these specific interactions between Btk and cell membrane are discussed.
Animals↗
[Ions and chromatin structure--morphologic and x-ray microanalytic findings].
It is quite common that the different procedures for isolation of nuclei make use of the purifying effect of sedimentation through concentrated sucrose. For this reason we investigated by light and electron microscopy the changes of chromatin structure in dependence on the amount and sort of ions present in the solution used for isolation and resuspension of nuclei. A decreasing concentration of monovalent cations (Na+, K+) leads to a swelling of the whole nuclei in consequence of the decondensation of the chromatin fibres. This change of nuclear structure can be reversed by small additions (0.5-1.5 mM) of divalent cations (Mg2+, Ca2+, Cu2+). Inasmuch as each change of the electrostatic balance within the nucleoplasm causes morphological alterations also the pH of the solution influences the chromatin structure. Data of X-ray-microanalysis have established the importance of divalent cations for the maintenance of a certain nuclear structure under conditions of low ionic strength.
Animals↗
An electron probe X-ray microanalysis study during organogenesis from internode-derived nodules of Humulus lupulus var. Nugget.
Elemental changes during the induction of organogenesis from internode-derived nodules of Humulus lupulus var. Nugget were studied by electron probe X-ray microanalysis (EPMA) of specimens submitted to physical fixation procedures. X-ray spectra were collected from cambial and cortical cells. Four days after explants inoculation an increase of K and Ca was detected in cells of both regions. Four to twelve days after explants inoculation an increase of Cu, Zn, Fe, S and Mn was therein detected. Values of Cu, Zn, Fe, K and S were lower in control explants than in induced explants 12 days after induction. Although S presented fluctuations it increased throughout the induction period. X-ray spectra collected from organogenic nodules revealed higher levels of Ca, K, Fe, P and S on peripheral regions where regeneration was occurring. Ca was mobilized in several directions, from inner regions of nodules towards their periphery at the onset of plantlet regeneration. Levels of Mg and Na were low or absent. Control explants neither formed nodules nor regenerated plantlets. The results suggest that EPMA can be used to study relative elemental changes during plant morphogenesis induction and enables the early establishment of organogenic regions in nodules.
Journal Article↗
Electron probe X-ray microanalysis of residual bodies in aged cultured human glial cells.
Secondary lysosomes of the residual body type are frequent in nondividing cells from phase III cultures of human glial cells. These organelles have previously been shown to be analogous to lipofuscin granules of postmitotic cells in vivo. Most recent studies favor the assumption that residual bodies mainly result from incomplete degradation within the lysosomal vacuome of endogenous cellular components such as mitochondria and endoplasmic reticulum. Since iron occurs in several metalloenzymes produced by such organelles, it should then be possible to demonstrate accumulated iron within residual bodies. X-ray dispersive analysis of sectioned biological material is often hampered by diffusion and dissolution during preparation, as well as by too low a concentration of the elements. In this study we cultured glial cells on Formvar-coated gold grids and studied them unsectioned, after brief glutaraldehyde fixation and freeze-drying, in a transmission electron microscope at 100 kV in TEM and STEM mode. It was then possible to demonstrate iron in residual bodies of aged cells, presumably because the type of preparation utilized does not permit much dissolution.
Aging↗
The effect of aluminium coating on elemental signals in X-ray microanalysis.
It has been determined that, in the normal range of aluminium coating thicknesses used to remove charge from non-conducting specimens in the electron microscope, no detectable influence on the elemental signals obtained in X-ray microanalysis is observed. This is in contrast to a previous report (Hopkins et al., J. Electron Microsc. Tech., 18:176-182, 1991) of a reduction in elemental signal with increasing aluminium coating thickness. An explanation of errors in the previous interpretation is provided.
Aluminum↗
Mercury-induced loss of K+ from yeast cells investigated by electron probe x-ray microanalysis.
According to Passow & Rothstein (1960), the mercury-induced loss of K+ from yeast cells is an all-or-none effect. This hypothesis was tested by analysing individual yeast cells by means of energy-dispersive X-ray microanalysis. A dual effect of mercury was observed. The cell population was split into two parts: one part consisted of cells that had suffered a (nearly) complete loss of K+- the number of these cells increased with increasing concentrations of HgCl2; the other consisted of cells that had only lost part of their K+ content--these cells showed a normal distribution around a central value that decreased with increasing concentrations of HgCl2. Our analysis shows that the effect of mercury is more complex than originally suggested and that, in addition to an all-or-none effect, a gradual loss of K+ occurs.
Copper↗
Deposition of bismuth by Yersinia enterocolitica.
Yersinia enterocolitica 8081c cultures in exponential growth were incubated for 1 h in 0.1% microcrystalline bismuth subsalicylate (BSS) suspensions. Scanning electron microscopy (SEM) revealed microcrystals directly bound to BSS-treated bacteria. Energy dispersive spectroscopy (EDS) X-ray microanalysis of the attached microcrystals confirmed that the crystals were the microcrystalline BSS. X-ray spectra positive for bismuth were also obtained by SEM-EDS X-ray microanalysis of whole bacteria, suggesting metal incorporation into the bacteria in regions absent of bound microcrystals. Transmission electron microscopy of thin sections of embedded preparations of BSS-treated exponential-growth-phase bacteria showed electron-dense deposits in the periphery of the bacteria. Y. enterocolitica cultures that were in stationary phase at the time of incubation with microcrystalline BSS showed no evidence of the electron-dense deposits and EDS spectra were negative for bismuth. Bacteria incubated in the absence of microcrystalline BSS also lacked electron-dense deposits. Scanning transmission electron microscopy used in conjunction with EDS X-ray microanalysis to view and analyze semi-thick sections (250-300 nm) of embedded preparations of BSS-treated bacteria in exponential growth confirmed that the electron-dense deposits at the periphery of the bacteria are the sites of bismuth depositions.
Bismuth↗
Ultrastructural localization of calcium, by electron-probe X-ray microanalysis, in the small intestine of suckling rats.
The subcellular distribution of calcium has been investigated in samples, from the intestinal mucosa of 10-day rats, prepared for X-ray microanalysis by various techniques designed to minimize the loss of this element. Calcium retention and its threshold of detection was most satisfactory in freeze-dried frozen thin sections. In resin-embedded samples the best retention of calcium was found in specimens fixed in absolute ethanol, embedded without osmication, and sectioned onto glycerol. The results of this investigation indicate the presence of calcium in the supranuclear vacuole of enterocytes in the distal intestine of the neonatal rat. This calcium is probably taken up during the endocytosis of material from the intestinal lumen. The same mechanism may also be important in the uptake of other metals by suckling animals.
Animal Population Groups↗
Microanalysis near particles and voids at grain boundaries.
Some of the problems of using high spatial resolution microanalysis in the vicinity of particles and voids in metal grain boundaries are discussed. New analytical results are presented for nickel based alloys, which suggest that elemental distributions in the region immediately adjacent to growing grain boundary particles and voids are often anisotropic.
Electron Probe Microanalysis↗
Use of coincidence techniques to improve the detection limits of electron spectroscopy in STEM.
A method of improving the detection limits of microanalysis using electron energy losses due to inner-shell excitation is proposed. This is based on coincidence detection of the energy-loss electrons with another signal which also results from inner-shell excitations, i.e., Auger electrons or characteristic X-rays. It is concluded that there will be a significant improvement in the detection of monolayers on a homogeneous monatomic substrate by using coincidence of energy-loss electrons with Auger electrons.
Electron Probe Microanalysis↗
Leaching and corrosion of polyvinyl chloride (PVC) tubes in a dialysis water distribution system.
PVC tubes, from the dialysis water distribution system of a 14 and a 7 year old plant, were analysed by scanner electron microscopy (SEM) and X-ray microanalysis (EDAX). Results showed that the leaching of material occurs depending on time of use. The phenomenon does not modify the chemical composition of the material. Results suggest that PVC alterations, induced by time, could support bacterial proliferation thus reducing the quality of dialysate.
Corrosion↗
Comparison of the methods of cathodoluminescence, electronprobe microanalysis, and calcium staining, applied to human aorta with isthmus stenosis.
Electron probe x-ray microanalysis is a useful method for studying pathologic and age-related calcification mechanisms in the aorta and in muscular arteries by means of elemental analysis in microareas. In the present investigation, this method was correlated with the histochemical alizarin-S-calcium staining and with cathodoluminescence analysis in the scanning electron microscope. Portions of the proximal region of a human aorta with isthmus stenosis was shock-frozen and sectioned in a cryostat. Serial sections were investigated by calcium staining, electron probe, and cathodoluminescence microanalysis. Using quantitative electron probe microanalysis of calcium and phosphorus, it was shown that the principal regions of calcium phosphate mineralization could be located using either alizarin-S staining or cathodoluminescence analysis. The advantage of the cathodoluminescence analysis is its higher lateral resolution compared with that of light microscopy, and the fact that no special staining is required. In addition, it was possible to obtain scanning images, thus providing additional information about the topology of the tissue surface, which is necessary to decide whether or not the section is suitable for microanalysis. Quantitative microanalysis is a valuable tool for basic research on calcified arteries. The results of the combined analysis in the proximal and distal regions as well as in the stenosis will be published in a later paper.
Aortic Coarctation↗
[Monocrystalline aluminum dental implants in animals: a study of the peri-implant tissue].
After the extraction of two molars in a dog's jaw, a single crystal alumina screw was implanted. Monthly radiographs were taken and analyzed by means of a video display computer (VDC) to obtain densitometric informations about the interface. After one year implantation, the bone segment containing the prosthesis was fixed in 4% paraformaldehyde, embedded in methacrylate and sectioned by a microtome saw. The results in light microscopy with ordinary and polarized light, in SEM and X-ray microanalysis, show the presence of a thick connective tissue layer interposed between the screw and the bone. The histological findings confirm the results obtained through the VDC analysis of the radiographic images.
Absorptiometry, Photon↗
Quantitative electron probe x-ray microanalysis of biological bulk specimens.
X-ray microanalysis of thick biological specimens is of considerable practical interest. Quantitative analysis of this kind of specimens poses some difficulties, and quantitative methods are less well developed than for thin sections. In this tutorial, the various parts of the ZAF-corrections are examined in some detail, and special attention is given to possible problems with the use of the ratio model. In quantitative analysis of metals (Z greater than 20) in biological bulk specimens, attention should be given to secondary fluorescence by the continuum. Various types of standards are compared, both with respect to homogeneity and with respect to their effect of quantitation with the ZAF-correction method. In both respects, organic standards of the 'gelatin' or 'resin' type perform better than do crystal standards. The use of relative intensities (P/B-ratios) in quantitative analysis of biological bulk specimens is considered. In most, but not all, cases use of P/B-ratios has advantages over the use of absolute X-ray intensities.
Crystallization↗
Ultrastructure of Trichophyton mentagrophytes stained with neutral red.
The ultrastructure of Trichophyton mentagrophytes cells stained with neutral red was investigated using electron microscopy and X-ray microanalysis. Fixatives containing molybdenum and chromium were used to prevent the outflow of neutral red. Electron-dense particles composed of metals and dye were observed exclusively in the vacuoles, which were increased in number and size, but not near the cell wall. Results indicate that neutral red passes directly through the fungal cell wall and is incorporated into the vacuoles.
Electron Probe Microanalysis↗