PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Electron Probe Microanalysis”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources
PubMed2003

Speciation of sulfur in individual aerosol particles from work places by wavelength-dispersive electron-probe microanalysis.

The oxidation state of sulfur has been determined by measuring the energy shift of the S K(alpha) line by wavelength-dispersive electron-probe microanalysis. On flat polished samples the energy shift between sulfate (S(+6)) and sulfide (S(-2)) was 1.3 eV, in good agreement with previous literature data. The observed energy shift of the S K(alpha) line is dominated by the change of the valence state of sulfur--the effects of co-ordination geometry and nearest neighbours are small. The relationship between the energy shift of the S K(alpha) line and the oxidation number of sulfur is linear, to a first approximation. The effect of particle geometry on the position of the S K(alpha) line is usually small and introduces an error of approximately half an oxidation number. The apparent sulfur valence states observed for individual aerosol particles from work places in a nickel refinery are highly variable and most probably result from different mixtures of the two end-members sulfide and sulfate.

Journal Article↗
PubMed1997

Assay of acetylcholinesterase activity and elemental composition in brain compartments by electron probe microanalysis.

Using histochemical techniques the distribution of acetylcholinesterase (AChE) activity in rat brain has been well established. These assays are based on the precipitation of a specific deposit containing copper-ferricyanide. The amount of locally deposited product is proportional to the AChE activity in the examined area of the section. Thus, the amounts of copper or (and) iron as the deposited histochemical labels mark the distribution and magnitude of the enzyme activity. The present protocol describes an approach to obtain by electron probe microanalysis (EPMA) a map of copper deposited in different brain regions via AChE histochemistry. EPMA allows a wide range of chemical elements to be analyzed. Thus, together with the determination of the copper concentration, elemental contents (Na, Cl, K and Ca) are measured as the specific environment for local AChE activity.

Acetylcholinesterase↗
PubMed2004

Uniformity and physical states of troglitazone in solid dispersions determined by electron probe microanalysis and microthermal analysis.

Solid dispersions of troglitazone with PVP K30 in a weight ratio of 1:2 were prepared by the closed melting method. Solid dispersions that exhibit different degrees of crystallinity (0 and 36%) were prepared by changing the charged amount of water, which functions as a plasticizer for PVP K30. Electron probe microanalysis (EPMA) and microthermal analysis (micro TA) of the solid dispersions were performed to investigate the uniformity and physical state of troglitazone in the solid dispersions. The EPMA study confirmed that troglitazone was dispersed homogeneously in the sample whose apparent crystallinity was 0%. However, the sample with a 36% crystallinity was heterogeneous. The micro TA study showed that the sample with a 36% crystallinity was present in two states, crystal and amorphous. EPMA and micro TA would be useful tools to confirm the uniformity and physical states, respectively, of solid dispersions.

Chemistry, Pharmaceutical↗
PubMed1997

Electron probe microanalysis and transverse microradiography studies of artificial lesions in enamel and dentin: a comparative study.

In cardiology and research involving the interactions between restorative materials and dental hard tissues, it is important for small changes in tooth mineral content to be measurable. Currently, transverse microradiography (TMR) is the most accepted tool for the above purpose. Electron Probe Microanalysis (EPMA) can yield both qualitative identification of elements and quantitative compositional information. The purpose of this study was to compare the mineral distribution in well-defined artificial lesions, in dentin and enamel, by the use of both TMR and EPMA on the same sample. The good correlation between the two sets of data validates EPMA as a technique and helps in the interpretation of its results. The data from TMR analysis are expressed as vol% of mineral, while EPMA gives the levels of Ca and phosphate in wt%. The conversion between the two sets of data is complicated by the fact that local density is, as yet, unknown.

Analysis of Variance↗
PubMed2002

Fluorescent labeling analysis and electron probe microanalysis for alveolar ridge augmentation using calcium phosphate cement.

Our previous histopathological study showed that the augmentation block, prepared from a calcium phosphate cement (CPC) mixed with H2O at powder to liquid ratio of 5 g/mL, placed on the alveolar bone ridge, was gradually replaced by natural bone. In the present study, fluorescent labeling analysis (FLA) and electron probe microanalysis (EPMA) were performed on the same surgical site of the above histopathological study. Fluorescent labeling agents, that would be incorporated into newly formed mineralized tissues, were injected into dogs intramuscularly twice a week during the 3 week period that ended 1 week before sacrifice. The specimens obtained from the block were subjected to FLA for assessing the extent of new bone formation and to EPMA for measuring the elemental (Ca, P, Mg) distributions. FLA results showed the presence of newly formed bone at 1 month after surgery. EPMA results showed that the elemental distributions in the augmentation site were similar to those of the residual bone area at 6 months after surgery. FLA and EPMA examinations also indicated that the implants were surrounded and fixed by natural bone chronologically. A CPC augmentation block is clearly useful for alveolar ridge augmentation and osteointegrated implant fixation.

Alveolar Process↗
PubMed1995

Scanning electron microscopy-electron probe microanalysis study of the interface between apatite and wollastonite-containing glass-ceramic and rabbit tibia under load-bearing conditions after long-term implantation.

Glass-ceramic implants containing oxy- and fluoroapatite [Ca10(PO4)6(O, F2)] and beta-wollastonite (CaSiO3) were studied under load-bearing conditions in a segmental replacement model in the tibia of the rabbit. A 16-mm segment of the middle of the tibial shaft was resected at a point distal to the junction of the tibia and the fibula. The defect was replaced by a 15 mm-long hollow, cylindrical implant that was fixed by intramedullary nailing using Kirschner wire. The implants were 9 mm in diameter and 15 mm long bearing a central hole 3.05 mm in dianeter. The rabbits used were killed 6 months, 1 year, 18 months, and 2 years after implantation. The interface between the bone and the glass-ceramic was investigated by scanning electron microscopy-electron-probe microanalysis (SEM-EPMA). None of the glass-ceramic implants broke, and the glass-ceramic had bonded directly to the bone tissue without any intervening soft tissue. A calcium-phosphorus layer (Ca-P layer) was observed at the glass-ceramic/bone interface. This layer was 30-100 microns thick at 6 months after implantation, 60-110 microns thick at 1 year after implantation, 80-200 microns thick at 18 months, and 120-350 microns thick at 2 years. At the lateral surface of the glass-ceramic uncovered by the bone, the calcium-phosphorus layer was 50-80 microns thick at 6 months after implantation, 250-450 microns thick at 1 year, 300 approximately 400 microns thick at 18 months, and 300 microns thick at 2 years. The thickness of the calcium-phosphorus layer increased moderately after long-term implantation. However, it was difficult to estimate the rate of increase in the thickness of calcium-phosphorus layer.

Animals↗
PubMed2001

Characterization of interglobular dentin and Tomes' granular layer in dog dentin using electron probe microanalysis in comparison with predentin.

The interglobular dentin (IG) and the Tomes' granular layer (TGL) as well as predentin are hypomineralized regions in dentin. Some previous studies proposed that the IG and the TGL are identical with difference only in size, whereas other suggested that they are distinct structures. In order to characterize their matrix components, the present study was designed to analyze the elements of calcium (Ca), phosphorus (P), and sulfur (S) in the IG and the TGL in comparison with predentin using the Electron Probe Microanalysis (EPMA). The TGL was highest in the concentration of both Ca and P among the hypomineralized regions followed by the IG and predentin, whereas predentin was the highest in the concentration of S followed by the IG and the TGL. Alcian blue staining suggested that the S elements identified with the EPMA are incorporated into the sulfated glycosaminoglycan chains of proteoglycans. The present study first demonstrated distinct characteristics of matrix components in the IG and the TGL, i.e., the IG is poorer in mineralization but much richer in a proteoglycan content than the TGL. The IG may originate from predentin because of their analogy, whereas the TGL may follow a different ontogeny.

Alcian Blue↗
PubMed2003

Material properties of subchondral bone from patients with osteoporosis or osteoarthritis by microindentation testing and electron probe microanalysis.

Cancellous bone from patients with osteoarthritis (OA) has a reduced material density and appears to be undermineralized. It is hypothesized that this will result in a reduction in the mechanical stiffness and strength of the bone matrix. In this study, bone was obtained from superior and inferior sites, subjected to relatively high and low loads, respectively, from human femoral heads retrieved after surgery for osteoporotic hip fracture (OP), or for hip arthroplasty due to OA. Microindentation testing was used to measure the hardness of cancellous bone at various depths from the subchondral bone plate. The elemental composition from immediately adjacent microscopic sites was determined using electron probe microanalysis (EPMA). Overall, OA bone was found to have hardness values that were 7% lower than those from OP bone. Bone from the inferior site was harder than that from the superior in both diseases except in female OP patients. There was no variation with depth below the subchondral plate and no difference between sexes. No difference was found in the composition of the bone from the different disease groups and no correlation was found between hardness and any of the composition measurements. Though only an indirect measurement of stiffness, the reduction in hardness values supports the hypothesis that OA bone has a reduced elastic modulus.

Aged↗
PubMed2000

[The electron probe microanalysis on oral precancer treated by garlic].

OBJECTIVE: To evaluate the effect of 4 kinds of trace elements on experimental oral precancer treated by garlic. METHODS: The palatal mucosae of 42 Wistar rats were painted with 0.5% of 4-nitroquinololine-1-oxide(4NQO) three times weekly for 7 weeks by coating method. Then the animals were divided randomly into two groups. The treatment group was treated three times weekly with garlic solution at the posterior hard palatal mucosae by coating method, and in the control group, the vehicle-distilled water was used instead of garlic solution. At the 5th and 8th weeks of the treatment and the 7th week after the treatment was stopped, some animals were killed. The palatal epithelial cells were prepared and surveyed by electron probe microanalysis. RESULTS: During the treating period, garlic improved the levels of epithelial cells' nuclei copper, selenium, molybdenum and extranuclei selenium, molybdenum(P < 0.01), but it decreased the contents of epithelial cells' extranuclei copper and extra- and intranuclei zinc(P < 0.01). CONCLUSIONS: Garlic can treat the oral precancer by improving the levels of epithelial cells' nuclei copper, selenium, and molybdenum and extranuclei selenium and molybdenum.

4-Nitroquinoline-1-oxide↗
PubMed1993

Microheterogeneity of subsarcolemmal sodium gradients. Electron probe microanalysis in guinea-pig ventricular myocytes.

1. The effect of stimulation on possible subsarcolemmal sodium accumulation was studied in ventricular myocytes (2 mM [Ca2+]o, 36 degrees C). By trains of eighteen paired voltage-clamp pulses (180 ms to 0 mV, 20 ms to -45 mV, 180 ms to +50 mV, 620 ms to -45 mV) unloaded contractions were potentiated to an optimum. 2. Potentiation reversibly enlarged and prolonged the diastolic tail currents due to Na(+)-Ca2+ exchange. Eighteen pulse pairs were estimated to provide a sodium influx that could increment the total intracellular sodium concentration (sigma Na(i)) by no more than 0.5 mM. 3. Potentiation reversibly increased the current at +50 mV and made it more noisy. Cell-attached recordings with a second electrode attributed this noise to the activation of K+ (Na) channels. In inside-out patches, a comparable channel activity was obtained with 40 mM sodium. Hence, the cell-attached recordings suggest that potentiation can increase intracellular sodium concentration to 40 mM. 4. Electron probe microanalysis (EPMA) measured sigma Na in a volume within 20 nm of the inner side of the sarcolemma. Potentiation reversibly increased sigma Na20nm to 40 +/- 7 mM. When stimulation was terminated, sigma Na20nm fell within 8 s to 37 +/- 8 mM and within 3 min to 19 +/- 6 mM. In unstimulated cells sigma Na20nm was 17 +/- 5 mM. 5. In potentiated cells, shock-frozen at early systole, sigma Na fell with a space constant of 28 nm from the sarcolemma to the centre; at 1 microns distance sigma Na was 12 +/- 3 mM. The steep gradient suggests that sodium does not freely diffuse and sigma Na20nm is controlled by transmembrane fluxes rather than by cell dialysis. 6. sigma Na20nm data were distributed with peaks at 5, 30 and 60 mM. Quantitative elemental digital imaging demonstrated patches with 60-80 mM sigma Na20nm alternating with others of 0-15 mM sigma Na20nm. This 'sodium microheterogeneity' suggests that Ca2+ efflux at low sigma Na20nm and K+(Na) channel activation at high sigma Na20nm can operate simultaneously.

Animals↗
PubMed1977

Electron probe microanalysis in the study of gallstones.

Detailed information on the structure and composition of gallstones was obtained using an electron probe microanalyser in conjunction with the other methods. Gallstones were studied layer by layer without greatly disturbing the arrangement of the materials present. Elements, including trace elements such as copper, iron, and manganese, were identified and their distributions mapped. The range of the method was extended to determine the character and distribution of certain chemical groups present by treating sections of gallstone with reagents which contained easily detected elements. The nature of the bonding of the sulphur in the stones was studied by examining the sulphur-X-ray spectrum. Pigmented sulphur-containing deposits were found to contain sulphur in a low valence state but taurine conjugates and the sulphate groups of mucosubstances were not detected. Microcrystalline apatite present in the stones contained some manganese and seemed to be implicated in the absorption of the low valence sulphur compound and in the nucleation of some stones.

Calcium↗
PubMed1995

"Standardless" quantitative electron probe microanalysis with energy-dispersive X-ray spectrometry: is it worth the risk?

"Standardless" procedures for quantitative electron probe X-ray microanalysis attempt to eliminate the need for standardization through calculation of standard (pure element) intensities. Either "first principles" calculations, which account for all aspects of X-ray generation, propagation, and detection, or "fitted standards" calculations, which use mathematical fits to measured intensities from a limited set of pure standards, can form the basis for standardless analysis. The first principles standardless analysis procedure embedded in the National Institutes of Health/National Institute of Standards and Technology comprehensive X-ray calculation engine and database, Desktop Spectrum Analyzer, has been tested against spectra measured on NIST standard reference materials, research materials, and binary compounds. The resulting distribution of errors is broad, ranging from -90% to +150% relative. First principles standardless analysis can thus lead to unacceptably large errors.

Electron Probe Microanalysis↗