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Results for “Electron Probe Microanalysis”

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At least 181 records · Page 10Linked to original sources

PubMed1996

Bone-bonding behavior of plasma-sprayed coatings of BioglassR, AW-glass ceramic, and tricalcium phosphate on titanium alloy.

The bone-bonding behavior of three kinds of bioactive ceramics coated on titanium alloy by the plasma-spray technique was investigated. Titanium alloy (Ti-6A1-4V) coated with BioglassR (45S5), apatite-wollastonite containing glass ceramic (AW), or beta-tricalcium phosphate (TCP) was prepared, and rectangular specimens were implanted into the tibial bones of mature male rabbits, which were sacrificed 8 or 24 weeks after implantation. The tibiae containing the implants were dissected out and subjected to detachment tests to measure the failure load. The bone-implant interface was investigated by Giemsa surface staining, contact microradiography, and scanning electron microscopy-electron probe microanalysis (SEM-EPMA). Eight weeks after implantation, the failure loads for implants coated with BioglassR, AW, and TCP were 1.04 +/- 0.94, 2.03 +/- 1.17, and 3.91 +/- 1.51 kg, respectively, and 24 weeks after implantation, the respective failure loads were 2.72 +/- 1.33, 2.39 +/- 1.30, and 4.23 +/- 1.34 kg. Failure loads of AW- and TCP-coated implants did not increase significantly with time. After the detachment test, breakage of the coating layer was observed. Bioactive ceramics can act as stimulants that induce bonding between bone and metal implants. However, failure load of metal implants coated with the bioactive ceramics was lower than that of bulk AW or TCP. It appears impossible to obtain a higher failure load using a bioactive-ceramic coating on titanium alloy. Histologically, the coating layer was found to become detached from the metal implant and the bone tissue bonded to the coating layer. SEM-EPMA observation revealed breakage of the coating layer, although bonding between bone and the coating layer was evident. A Ca-P-rich layer was observed at the interface between bone and the AW coating, and a Ca-P-rich and a Si-rich layer were observed at the interface between bone and the BioglassR coating. For clinical application, it would seem better to use coated metal implants for short-term implantation. However, there is a possibility of breakage of the coating layer because of both dissolution of the bioactive ceramic and mechanical weakness at the interface between the coating layer and the metal implant.

Alloys↗

PubMed1985

Ultrastructure and chemical composition of calcite urinary calculi in Chinese swamp buffalo.

Four urinary calculi, derived from Chinese swamp buffalo, were studied by using qualitative chemical analysis, X-ray diffraction, scanning electron microscopy and qualitative energy dispersive (electron probe) microanalysis. Qualitative chemical analysis showed that the predominant ions were calcium and carbonate with small amounts of magnesium and ammonium. X-ray diffraction confirmed that the calculi were primarily composed of calcium carbonate (calcite). On ultrastructural examination, three apparently distinct structural regions were identified in the calculi: outer large laminations; cavities containing variable numbers of small spheres and rods; and large spheres. There did not appear to be material that acted as a nidus and all regions, on qualitative electron probe analysis, contained primarily calcium with trace amounts of magnesium, phosphorus, potassium and chloride. It was concluded that calcite calculi in Chinese swamp buffalo are probably formed through a process of asynchronous layering and that nidus formation may not be necessary. Moreover, the ultrastructure of the calcite calculi is similar to that reported for siliceous calculi in ruminants and this suggests that similar factors may be involved in their formation.

Animals↗

PubMed1995

Artefacts in electron microscopy: ultrastructural features of chrysiasis.

Eleven cases of chrysiasis have been studied ultrastructurally and by electron probe microanalysis. Tissue samples were examined both with and without osmium and uranyl acetate staining. There was a significant morphological difference in the appearance of the gold deposits within aurosomes between the two groups. The untreated group showed finely granular deposits, often arranged in a linear fashion. Aurosomes from samples treated with osmium and uranyl acetate showed more electron-dense deposits and star-like formations. We propose that treatment of the tissue with osmium and uranyl acetate causes a change in the electron microscopic appearance of aurosomes, including the formation of the characteristic star-like aurosomes.

Antirheumatic Agents↗

PubMed1989

Detection of cationic and non-cationic markers in the rat glomerulus by electron probe analysis.

Acidic glycans (glomerular polyanion substances) in the rat kidney were visualized ultrastructurally by three cationic markers: colloidal iron, ruthenium red, and polyethylenimine-phosphotungstic acid (PEI-PTA). Heavy metal atoms (Fe, Ru and W) were detected in ultrathin sections by energy-dispersive electron probe microanalysis (EPMA). Characteristic peaks of the locally bound elements were obtained in spectra derived from the dense structures seen by transmission electron microscopy (TEM)--i.e. the glycocalyx of podocytes and/or the polyanion sites in the lamina rara externa of the glomerular basement membrane. Weaker signals were emitted by some extraglomerular structures. This finding may reflect a low concentration of glycans in structures lacking apparent density by TEM, and/or incomplete specificity of the markers, partial dislocation of reactive substances or the presence of an endogenous element (Fe). Experimental argyrosis was elicited by the peroral administration of silver nitrate. Dense Ag precipitates were seen chiefly in the lamina densa and characteristic peaks of silver were displayed in this site by EPMA, and was best demonstrated in non-contrasted sections. A single i.v. injection of Ag proteinate failed to produce glomerular pigmentation. The only dense granular product in tubular cells yielded characteristic peaks of Fe (endogenous siderosomes) but EPMA excluded detectable amounts of silver.

Animals↗

PubMed1989

A histological study of calcium pyrophosphate dihydrate crystal-deposition disease.

Synovial, meniscal, articular cartilage, and other connective tissue from fifty-seven patients who had calcium pyrophosphate dihydrate crystal-deposition disease was examined by light microscopy, electron microscopy, and electron-probe microanalysis. Safranin O-positive hypertrophic chondrocytes that contained proteoglycans were observed in the tissues of each patient. Microcrystals that were suggestive of early precipitation of crystals were found in the degenerating matrix surrounding hypertrophic chondrocytes. The matrix contained electron-dense amorphous material, including proteoglycans and debris of cellular components. The microcrystals were often seen in contact with degenerating collagen fibers. There was never any histological evidence of formation of crystal in the areas that had no hypertrophic chondrocytes. Chondrocytes of this kind, surrounded by characteristic degenerating matrix, were never observed in the articular tissue from sixty-one patients who had only osteoarthritis. On the basis of our results, we speculate that electron-dense amorphous material containing proteoglycans and debris of cellular components, and the degenerating collagen fibers that were seen around the hypertrophic chondrocytes, may play important roles in the formation of calcium pyrophosphate dihydrate crystals.

Adult↗

PubMed1987

Hydroxyapatite deposition in osteoarthritic articular cartilage of the proximal femoral head.

Hydroxyapatite crystal deposition in the articular cartilage of the proximal femoral head was examined by using light and electron microscopy and electron probe microanalysis. The hydroxyapatite deposition was significantly more frequent in patients with osteoarthritis (40.7%, 22 of 54) than in control subjects (6.0%, 3 of 50) (P less than 0.001). Initial deposition of needle-like crystals was always seen on or within the electron-dense, amorphous material around the degenerating hypertrophic chondrocytes. Matrix vesicles were rarely seen in the calcifying areas.

Cartilage, Articular↗

PubMed1991

Secretory granule calcium loss after isolation of rat alveolar type II cells.

Morphological change and lamellar body loss suggests that alveolar type II cells rapidly de- or redifferentiate after several days of primary culture. To determine whether type II cells or lamellar body compositional changes precede these obvious morphological changes, we examined the in situ elemental composition of lamellar bodies and type II cells from intact lung and at different times after isolation using electron probe microanalysis (EPMA). Isolated cells were prepared by standard methods and plated on either tissue culture plastic or kept in suspension with stirrer flasks. Cell pellets obtained at 0, 3, 24, and 48 h after isolation were rapidly frozen, and thin freeze-dried cryosections were prepared and examined cold in a transmission electron microscope equipped for EPMA. Eight to ten type II cells from each of three to four different preparations for each time period were analyzed. A rapid, progressive, and sustained fall in lamellar body calcium and sulfur content occurred by 48 h of primary culture, suggesting rapid alteration in calcium and protein metabolism by type II cells and/or lamellar bodies after isolation. Also, marked changes in type II cell cytoplasmic Na and K occurred in freshly isolated cells, with incomplete normalization by 48 h. Culture on laminin-enriched Matrigel for 1 wk increased both lamellar body calcium or sulfur content, but 100 nM dexamethasone had no effect. Lamellar body calcium accumulation appears to be a very sensitive index of differentiated type II cell function.

Animals↗

PubMed1980

Evaluation of a preparative method for x-ray microanalysis of soft tissues.

We have adapted the cryopreparative methods designed for the radioautography of diffusible substances (Stumpf and Roth, 1966, 1967) to produce freeze-fried sections of soft tissues for electron probe microanalysis. This report concerns the evaluation of these methods for use with X-ray microanalysis with particular reference to: (1) the preservation of cellular morphology, (2) the introduction of structural artefact by ice crystal formation, (3) the preservation of natural elemental distributions under experimental conditions where known quantities of diffusible elements are present, (4) the effects of ice crystal formation upon possible artefactual elemental redistributions, (5) the effect of section thickness on elemental quantitation, and (6) the effect of tissue excision on element translocation. Freeze-dried sections were prepared from mouse pancreas and from 20% (w/v) solutions of bovine serum albumin (BSA) and gelatin containing known amounts of inorganic salts and were analysed in a scanning electron microscope fitted with energy dispersive X-ray detecting equipment. With the preparative methods used, the morphology of pancreatic acinar cells was well preserved. Acinar cell boundaries, nuclear boundaries, chromatin, nucleoli, ergastoplasm and zymogen granules were readily discernible. Ice crystals were present within sections of BSA, but 70% had a cut surface area < 1 micrometer2 and over 90% had a cut surface area of < 2 micrometer2. Characteristic peak-to-continuum ratios of elements in the BSA sections remained constant over an order of magnitude change in magnification. Elemental redistributions were not detected until the magnification was such that the analysed area fell totally within the confines of a single ice crystal. No differences in elemental peak-to-continuum values were obtained between 2 and 4 micrometer sections of the gelatin-salt solution. Tissue excision did not cause element translocations when compared to tissues frozen in situ. We conclude that this method is valid for preparing tissues for microanalysis under our conditions (analysis of nuclear, cytoplasmic, and secretory compartments) and is limiting only when analyses are conducted at very high magnifications.

Animals↗

PubMed1988

Sn in the Ag-Hg phase of dental amalgam.

In a recent study, Sarkar and Eyer (1986) studied an amalgam which was formed using a unique procedure. Based on their results, they concluded that the solubility of Sn in the Ag-Hg (gamma 1) phase of dental amalgam was virtually nil (less than 0.25 wt%). This finding is contrary to the published results of other investigations. The purpose of the present study was to clarify these disparate findings. A low-copper dental amalgam was examined by electron probe microanalysis. This amalgam was selected because it exhibits unusually large gamma 1 grains (10 microns). Because the influence of the electron-analyzing beam can be completely contained within these large grains, grain boundaries or peripheral phases would not be excited, and a valid analysis of the gamma 1 grains themselves could be made. The analyses showed significant Sn contents of 2.0-3.0 wt%. Analyses of areas which contained grain boundaries showed slight or no differences in Sn content compared with that for the grains alone. Furthermore, secondary electron scans of this dental amalgam failed to reveal the intergranular precipitates of Sn-Hg observed by Sarkar and Eyer (1986) in their amalgam. These different results can be explained by the fact that the unique amalgam investigated by Sarkar and Eyer does not exhibit the same diffusional patterns as does dental amalgam, and that the composition of the gamma 1 in the two amalgams is not the same. The final conclusion is that the Ag-Hg (gamma 1) phase in dental amalgam does indeed contain a significant amount of Sn.

Dental Amalgam↗

PubMed1986

[Sites of aluminum accumulation in bone marrow: study using electron microscopy, ionic microscopy and X-ray microanalysis].

Two methods of analytical microscopy have been used to study the distribution of aluminum in bone marrow of rats intoxicated by aluminum gluconate. Images of the distribution of aluminum in a field of 250 microns in diameter were obtained by analytical ion microscopy. They show that this element was concentrated in spots, associated with iron or alone, in the cytoplasm of some cells. Electron Probe Microanalysis (EPMA) has shown that aluminum concentration occurred in cells of the reticulo-endothelial system, principally in the reticular cells of erythroblastic islets. In cells of the reticuloendothelial system, aluminum was observed in intracytoplasmic organelles having ultrastructural characteristics of lysosomes or phagolysosomes. In these organelles, aluminum is always associated with phosphorus and sometimes with iron. No cytoplasmic or nuclear aluminum accumulation was detected in any other variety of bone marrow cells. The consequences of the selective accumulation of aluminum in the cytoplasm of reticular cells of erythroblastic islets for the maturation of erythrocytes are discussed.

Aluminum↗

PubMed1989

Cellular mechanisms of toxicity and tolerance in the copper-loaded rat. III. Ultrastructural changes and copper localization in the kidney.

The distribution of copper and related changes have been studied in copper-loaded rat kidneys at the ultrastructural level by X-ray electron probe microanalysis, in order to clarify the pathogenesis of copper-induced damage and subsequent recovery in this organ. Male rats fed a high copper diet (1500 ppm) for 16 weeks were killed at intervals; their kidneys were removed and portions of kidney cortex fixed in 4% paraformaldehyde and 2% glutaraldehyde for electron microscopy: other samples were analysed for copper by AA spectrophotometry. Increasing copper accumulation was associated with progressive PCT cell disarray and characterized by irreversible nuclear damage coincident with the intranuclear accumulation of Cu, S, P, and Ca. Copper was also identified within structurally intact lysosomes associated with Zn and Fe (Type I lysosomes) or P and S (Type II lysosomes, putative Cu-MT). Subsequent copper decline and tubular recovery was associated with the facilitated lysosomal sequestration of copper and excretion of copper-containing cell products into the tubule lumina, Cu-MT and alpha-2 urinary protein-copper. The cytotoxicity of copper in the kidney, as well as the liver, is associated primarily with irreversible nuclear damage, whereas lysosomal copper sequestration protects the cell from injury.

Animals↗

PubMed1980

Localization of calcium in presynaptic nerve terminals. An ultrastructural and electron microprobe analysis.

Ultrastructural techniques and electron probe microanalysis were used to determine whether or not the smooth endoplasmic reticulum (SER) within presynaptic nerve terminals is a Ca-sequestering site. The three-dimensional structure of the SER was determined from serial sections of synaptosomes. The SER consists of flattened cisterns that may branch and are frequently juxtaposed to mitochondria. To investigate intraterminal Ca sequestration, synaptosomes were treated with saponin to disrupt the plasmalemmal permeability barrier. When these synaptosomes were incubated in solutions containing Ca, ATP, and oxalate, electrondense Ca oxalate deposits were found in intraterminal mitochondria, SER cisterns, and large vesicular profiles. Saponin-treated synaptosomes that were incubated in the presence of mitochondrial poisons contained electron-dense deposits within SER cisterns and large vesicular profiles, but very rarely in mitochondria. Similar deposits were observed within saponin-treated synaptosomes that were not post-fixed with OSO4, and within saponin-treated synaptosomes that were prepared for analysis by freeze-substitution. Electron-probe microanalyses of these deposits confirmed the presence of large concentrations of Ca. When oxalate was omitted from the incubation solutions, no electron-dense deposits were present in saponin-treated synaptosomes. In other control experiments, either the Ca ionophore A23187 or the Ca chelator EGTA was added to the incubation media; electron-dense deposits were very rarely observed within the intraterminal organelles of these saponin-treated synaptosomes. The data indicate that presynaptic nerve terminal SER is indeed a Ca-sequestering organelle.

Adenosine Triphosphate↗

PubMed1983

Bone cysts containing silicone particles in bones adjacent to a carpal silastic implant.

Silastic implants for a wide variety of medical purposes are in current and frequent use worldwide. Only recently there have been reports of the migration of silicone to the surrounding tissues via lymphatics. In the present material of nine cases with carpal implants followed for more than two years, bone cysts developed in the surrounding bones on five occasions. The only cysts so far investigated thoroughly contained foreign body reaction, and silicone could be detected by electron probe microanalysis. A long-term follow-up is suggested whenever these implants are used.

Adult↗

PubMed1989

Cellular mechanisms of toxicity and tolerance in the copper-loaded rat. II. Pathogenesis of copper toxicity in the liver.

The distribution of copper has been studied in the liver of the copper-loaded rat at the ultrastructural level by X-ray electron probe microanalysis in order to clarify the pathogenesis of copper-induced damage. Male rats fed a high copper diet (1500 ppm) for 16 weeks were killed at intervals; their livers were removed and fixed in 4% paraformaldehyde and 2% glutaraldehyde for electron microscopy and were analyzed for copper by AA spectrophotometry. Three different forms of lysosomes were identified with respect to their morphology and X-ray emission profiles: Type I lysosomes appeared early and contained iron and zinc in addition to markedly elevated copper peaks, whereas later appearing Type II lysosomes included sulfur and phosphorus in addition to copper. Type III lysosomes were associated with the recovery period and contained much reduced elemental residue. Degenerative changes were not observed in any of the three types of lysosomes. Copper and other elemental residues, including sulfur, were also identified within the hepatic parenchymal cell nuclei and by contrast were associated with irreversible nuclear damage. Nuclear copper is directly injurious to this organelle and responsible for the subsequent cell death whereas copper contained within lysosomes is apparently innocuous.

Animals↗

PubMed1998

Improvement of bond strength in metal-ceramic systems using a gold intermediate layer.

The mechanism of bonding between metal and ceramic in systems using the functionally graded method with pure gold and gold mixture as a primer was examined. Four types of samples, porcelain, porcelain-gold, porcelain-metal and porcelain-gold-metal were prepared. The gold intermediate layer was fired at 1000 degrees C. For porcelain and metal, low-fusing opaque, body porcelain and palladium alloy were used. The intermediate layer was composed of three layers; pure gold, gold-palladium and gold-porcelain layer. During the bending test of each sample, the porcelain peeled away from the porcelain-metal system, while porcelain with the gold intermediate layer remained on the metal surface even after maximal loading. The bond strength of the porcelain-gold-metal system was much higher than that of the porcelain-metal system, and the toughness of the former was much greater than that of the latter. Laser microscopy and scanning electron microscopy (SEM) showed a smooth interface between the intermediate layer and the metal which suggested proper chemical bonding, and no gap was observed. At the interface between the porcelain and the gold intermediate alloy, a good mechanical anchor lock was observed. Electron probe microanalysis (EPMA) showed a clear distribution of each element (e.g. Si, Au and Pd) in the porcelain, gold intermediate layer and metal frame.

Dental Bonding↗

PubMed1994

Preparation of unfixed and undecalcified frozen sections of adult rat periodontal ligament during experimental tooth movement.

The upper first molars of adult male rats were moved for 7 days and unfixed, undecalcified frozen sections of the molar periodontal ligament were prepared and observed. The upper jaws of the rats were immersed rapidly in liquid nitrogen and sectioned with a cryostat using a super hard knife. Five micrometer serial sections were cut, collected, freeze-dried and observed with both light and scanning electron microscopy. Electron probe microanalysis (EPMA) was also performed on the sections. On the tension side of the periodontal ligament, periodontal fibers were stretched and the osteoblasts were aligned on the osteoid, which showed metamasia with the toluidine blue stain. On the pressure side where the periodontal ligament was extremely compressed, tissue degeneration was caused by tooth movement and the osteoclasts were observed on the bone surface adjacent to the degenerating tissues. Scanning electron microscopy revealed a network arrangement of the collagen fiber bundles on the tension side, but not on the pressure side of the periodontal ligament. The spectrum obtained from EPMA of the osteoid demonstrated X-ray (Ka) peaks of Na, P, S, K and Ca.

Animals↗

PubMed1985

Cross-linked polypentapeptide of elastin as a calcifiable matrix: molecular weight dependence.

The polypentapeptide, (L X Val1-L X Pro2-Gly3-L X Val4-Gly5)n, when cross-linked by gamma-irradiation was shown to calcify when exposed to dialysates of calcium and phosphate augmented fetal bovine sera and the molecular weight dependence of this calcification is investigated. Five molecular weight fractions, labeled I to V in order of increasing polymer size from under 12,000 dalton (I), that is, n less than 30, to over 100,000 daltons (V), that is, n greater than 240, were gamma-irradiation cross-linked at 10-12 MRAD to form matrices I-V. Calcium-45 was used to follow the time course and relative amount of calcium uptake from the sera. Scanning electron microscopy and electron probe microanalysis were used to characterize the extent of matrix calcification. All matrices took up calcium-45 from the sera; however, only matrices formed from polypentapeptide with n greater than 100 calcified, that is, matrices III, IV, and V. Matrix V with n greater than 240 calcified massively and in a manner comparable to chemically cross-linked polypentapeptide with n approximately 40 using nonaugmented sera. Presumably, gamma-irradiation results in chain breakage. The gamma-irradiation cross-linked matrices with values of n ranging from under 30 to greater than 240 establish the molecular weight dependence of matrix calcification.

Animals↗

PubMed1992

Hexahedrally based crystals in human tooth enamel.

Mg-containing calcium phosphate crystals including pseudocuboidal, rhombohedral shapes and groupings of quadrangular blades cubically arranged were found in human tooth enamel by scanning electron microscopy and by electron probe microanalysis. In caries-free old enamel, these hexahedrally based crystals measuring 0.5-2.5 microns in length were observed in some crevices of tufts and lamellae. The crystals were rarely seen in the inner crevices of caries-free exfoliated deciduous enamel and none could be seen in sound young enamel. In brown-coloured old enamel possessing arrested caries with lamellae, some of the lamellae contained crystals measuring 0.1-1.5 mu in length adjacent to half-dissolved prisms. These crystals, identified as Mg-containing whitlockite, will grow during a long period after eruption of the tooth or during the enamel caries process.

Aged↗