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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↗
PubMed2006

SEM evaluation of neodentinal bridging after direct pulp protection with mineral trioxide aggregate.

The purpose of this study was to observe the basic morphology and determine the chemical composition of neodentinal bridges adjacent white mineral trioxide aggregate (WMTA) when used as a direct pulp capping material. The experimental procedures were performed on six intact dogs' teeth. The pulps were exposed and cavities were filled with WMTA. After 2 weeks, neodentinal bridge formation was evaluated by scanning electron microscope (SEM) of cross-sections of the specimens and electron probe microanalysis (EPMA) of the pulpal surfaces. Results of SEM observation showed that the most characteristic reaction of pulp cells was the intimate connection of cell processes and secreted extracellular fibres with the crystals of the pulp capping material. Results of EPMA indicated that the mineralisation of neodentinal bridge formation occurred progressively from the periphery to the central area. Based on these results, it appears that WMTA has the potential to be used as a direct pulp capping material during vital pulp therapy.

Aluminum Compounds↗
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↗
PubMed1993

Electron microprobe analysis in periodontal guided tissue regeneration.

Electron microprobe analysis was used to determine the evolution of Ca, P and S in regenerated tissue surrounding incisors roots after periodontal treatment with guided tissue regeneration. Our results, which showed increased Ca and P, and decreased S are discussed in relation to the process of mineralization electron probe microanalysis with potentially provided an accurate means of assessing the degree of mineralization in extremely small tissue samples.

Calcium↗
PubMed2003

Thermal expansion and microstructural analysis of experimental metal-ceramic titanium alloys.

UNLABELLED: Statement of problem Low-fusing porcelains for titanium veneering have demonstrated inferior color stability and metal-ceramic longevity compared to conventional porcelains. PURPOSE: This study evaluated the microstructure and thermal expansion coefficients of some experimental titanium alloys as alternative metallic substrates for low-fusing conventional porcelain. MATERIALS AND METHODS: Commercially pure titanium (CP Ti) and various metallic elements (Al, Co, Sn, Ga, In, Mn) were used to prepare 8 titanium alloys using a commercial 2-chamber electric-arc vacuum/inert gas dental casting machine (Cyclarc). The nominal compositions of these alloys were the following (wt%): I: 80Ti-18Sn-1.5In-0.5Mn; II: 76Ti-12Ga-7Sn-4Al-1Co; III: 87Ti-13Ga; IV: 79Ti-13Ga-7Al-1Co; V: 82Ti-18In; VI: 75.5Ti-18In-5Al-1Co-0.5Mn; VII: 85Ti-10Sn-5Al; VIII: 78Ti-12Co-7Ga-3Sn. Six rectangular wax patterns for each test material (l = 25 mm, w = 3 mm, h = 1 mm) were invested with magnesia-based material and cast with grade II CP Ti (control) and the 8 experimental alloys. The porosity of each casting was evaluated radiographically, and defective specimens were discarded. Two cast specimens from CP Ti and alloys I-VIII were embedded in epoxy resin and, after metallographic grinding and polishing, were studied by means of scanning electron microscopy and wavelength dispersive electron probe microanalysis. One specimen of each material was utilized for the determination of coefficient of thermal expansion (CTE) with a dilatometer operating from room temperature up to 650 degrees C at a heating rate of 5 degrees C/minute. RESULTS: Secondary electron images (SEI) and compositional backscattered electron images (BEI-COMPO) revealed that all cast specimens consisted of a homogeneous matrix except Alloy VIII, which contained a second phase (possibly Ti(2)Co) along with the titanium matrix. The results showed that the coefficient of thermal expansion (CTE) varied from 10.1 to 13.1 x 10(-6)/ degrees C (25 degrees -500 degrees C), depending on the elemental composition. CONCLUSION: The CTE of titanium can be considerably changed by alloying. Two-phase alloys were developed when alloying elements were added in concentrations greater than the maximum solubility limit in alpha-titanium phase.

Aluminum↗
PubMed1999

Elemental analysis and clinical implications of calcification deposits associated with silicone breast implants.

Calcification of the fibrous capsule surrounding silicone breast implants is a well-recognized occurrence that increases with time following implantation. These mineralized deposits potentially confound mammographic breast cancer surveillance already made difficult by the obscuring effects of silicone breast implants. The authors performed elemental analysis of silicone breast implant-associated calcifications to define better their chemical composition as related to mammographic and clinical significance. Electron probe microanalysis and infrared spectroscopy revealed all of the calcification deposits to be calcium complexed with tribasic phosphate. No evidence of calcium oxalate, calcium carbonate, silicone, or talc was observed. Caution must be employed in interpreting mammograms in women with silicone breast implants as well as those who have had their silicone breast implants removed. High-density mammographic calcifications indicative of calcium phosphate associated with a silicone breast implant may represent an accepted consequence of implantation or nearby carcinoma. We recommend baseline mammography on women who have had their silicone breast implants removed to prevent unnecessary fine-needle aspiration or tissue biopsy of retained breast capsule calcifications during subsequent routine surveillance for carcinoma.

Breast↗
PubMed2004

Monolithic columns with a gradient of functionalities prepared via photoinitiated grafting for separations using capillary electrochromatography.

Stationary phases for capillary electrochromatography with a longitudinal gradient of functionalities have been prepared via photoinitiated grafting of polymer chains onto the pore surface of a porous polymer monolith. In order to achieve the desired retention and electroosmotic flow, the hydrophobic poly(butyl methacrylate-co-ethylene dimethacrylate) monolith with optimized porous properties was grafted with a layer of ionizable polymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid). A moving shutter and a neutral density filter were used to control the dose of UV light received at different locations along the monolith in order to create the longitudinal gradient of functionalities. Formation of the desired gradients was confirmed using electron probe microanalysis of different locations along the column. The preparation technique significantly affects performance in the CEC mode as demonstrated on the separations of a model mixture using columns both with homogeneous distribution of grafts and with a gradient of functionality. Columns grafted with the gradient of functionalities were found superior to those functionalized uniformly. A comparison of the performance of the gradient column with another containing evenly distributed functionalities showed the performance benefits of the "gradient" column.

Electrochemistry↗
PubMed1975

Renal sodium-potassium adenosine triphosphatase. Optical localization and x-ray microanalysis.

The distribution of sodium-potassium adenosine triposphatase (Na-K-ATPase) activity in kidney sections has been studied by a method based on the hydrolysis of p-nitrophenyl phosphate in alkaline medium containing dimethyl sulfoxide. The products at each stage in the reaction sequence have been subjected to electron probe microanalysis. The initial product was identified as a mixture of KMgPO4 and Mg(PO4)2, and sequential analysis demonstrated the linearity of conversion of this product to a visible form. In human, rabbit and rat kidneys the distribution of activity was found to be essentially identical, with highest levels located in thick ascending limbs and distal convoluted tubules. The initial reaction was completely potassium dependent and was inhibited by ouabain in concentrations reflecting the relative sensitivity of microsomal Na-K-ATPase in each species. Measurement of initial product phosphorus by means of the electron probe is presented as a practical technique for direct quantitation of Na-K-ATPase activity in identified tubule segments.

Adenosine Triphosphatases↗
PubMed1996

Ultrastructure of selected struvite-containing urinary calculi from cats.

OBJECTIVE: To elucidate the ultrastructural details of struvite-containing urinary calculi from cats. DESIGN: Specimens studied were inclusive of the range of textures visible during preliminary analysis by use of a stereoscopic dissecting microscope. Textural types, which were used to infer crystal growth conditions, were differentiated with regard to crystal habit, crystal size, growth orientation, and primary porosity. SAMPLE POPULATION: Thirty specimens were selected from a collection of approximately 1,600 feline urinary calculi: 20 of these were composed entirely of struvite, and 10 consisted of struvite and calcium phosphate (apatite). PROCEDURE: Qualitative and quantitative analyses of specimens included use of plain and polarized light microscopy, x-ray diffractometry, scanning electron microscopy with backscattered electron imagery, x-ray fluorescence scans, and electron probe microanalysis. RESULTS: Four textural types were recognized among struvite calculi, whereas 2 textural types of struvite-apatite calculi were described. CONCLUSIONS: The presence of minute, well interconnected primary pores in struvite-containing urinary calculi from cats is an important feature, which may promote possible interaction of calculi with changes in urine composition. CLINICAL RELEVANCE: Primary porosity, which can facilitate interaction between the calculus and changing urine composition, may explain the efficacy of dietary or medicinal manipulations to promote the dissolution of struvite-containing uroliths from this species.

Animals↗
PubMed2003

Effect of smear layer on root demineralization adjacent to resin-modified glass ionomer.

The cariostatic effect of resin-modified glass ionomer (RMGI) on secondary root caries is well-documented. However, this beneficial effect may be dependent upon the mode of cavity surface treatment. To investigate this relationship, we studied 4 cavity surface treatments prior to the placement of RMGI: no treatment (None), polyacrylic acid (PAA), phosphoric acid (H(3)PO(4)), and Scotchbond Multi-Purpose adhesive (SMP) as a control. Specimens were aged for two weeks in synthetic saliva, thermocycled, and subjected to an artificial caries challenge (pH 4.4). Polarized light microscopy (PLM) and microradiography (MRG) showed significantly less demineralization with the H(3)PO(4) cavity surface treatment as revealed by ANOVA and Tukey's multiple comparisons (p < or = 0.05). Dentin fluoride profiles determined by electron probe microanalysis (EPMA) supported PLM and MRG findings. It may be concluded that removal of the smear layer with phosphoric acid provides significantly enhanced resistance to secondary root caries formation adjacent to RMGI restorations.

Acid Etching, Dental↗
PubMed2000

Assessment of X-ray photoelectron spectroscopy for analysis of particulate pollutants in urban air.

XPS was used to determine hourly and seasonal changes in urban airborne airborne particulates collected in London, UK. Particles were collected on a Burkard spore trap and on PTFE filters for hourly and daily readings, respectively, at periods during the summer and winter. Analysis within 24 h of collection was advisable to avoid build-up of surface contamination from the atmosphere. Carbon and oxygen species dominated the particulate surface with traces of Na+, Mg2+, Ca2+, SiO2, Cl-, NH4+, NO3- and SO4(2-) present. Major species could not be identified on particles collected by the Burkard spore trap as the peaks from the particles coincided with peaks from the tape in the O 1s and C 1s regions. In addition, particle loads were insufficient to establish changes in surface chemistry of the remaining trace species on an hourly basis. Carbon species could be identified for particles collected on PTFE filters as the binding energies for particles and PTFE are separated by 8 eV in the C 1s region. Three regions were identified, namely C-H/C-C, C-O/C-N and C=O/COO-. There was evidence of higher levels of soot during the winter due to more anthropogenic activity, which is in agreement with other data. Fe was a major element detected by electron probe microanalysis in the bulk of winter particles but not on the surface, implying an organic coating on the particles sufficiently thick (> 2 nm) to absorb the Fe photoelectrons.

Air Pollutants↗
PubMed2005

Chemical differences between white and gray mineral trioxide aggregate.

The purpose of this research was to determine and compare the composition of white mineral trioxide aggregate and gray mineral trioxide aggregate. Electron probe microanalysis results indicated that lime (CaO), silica (SiO2), and bismuth oxide (Bi2O3) were the dominant compounds in each case and were present at comparable levels in either of the types of mineral trioxide aggregate analyzed. It was concluded that the most significant differences observed were between the measured concentrations of Al2O3 (+122%), MgO (+130%), and especially FeO (+1000%) when gray mineral trioxide aggregate was compared with white mineral trioxide aggregate.

Aluminum Compounds↗
PubMed1995

Bone-bonding behavior of three heat-treated silica gels implanted in mature rabbit bone.

Silica gel has been reported to induce apatite nucleation on its surface in vitro and it can act as a stimulant that induces formation of chemical apatite (Ca-P) layers on the surfaces of bioactive glass-ceramics. In this study, apatite formation in response to and the bone-bonding behavior of silica gels implanted in the tibiae of mature rabbits were studied. Implants were made from three silica gels treated at 400, 800, and 1000 degrees C, and the effects of such heat treatment on the above parameters were investigated. The silica gel was made by hydrolysis and polycondensation of tetraethoxysilane in aqueous solution containing polyethylene glycol. Rectangular implants (15 mm x 10 mm x 2 mm) of each heat-treated silica gel were implanted into both tibial bones of mature male rabbits, which were killed 4 or 8 weeks after implantation, and the tibiae containing the implants were dissected out. The bone-implant interfaces were investigated using Giemsa surface staining, contact microradiography, scanning electron microscopy-electron probe microanalysis, and X-ray diffraction. Histologically, no bonding of bone to any of the silica gels was observed at any time postimplantation. Soft tissue was observed at the bone-silica gel interface, but there were no giant foreign body or inflammatory cells. A Ca-P-rich layer was observed only on small areas of the surfaces of the silica gels treated at 400 and 800 degrees C 4 and 8 weeks after implantation. X-ray diffraction analysis confirmed the presence of hydroxyapatite in these Ca-P-rich layers.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗