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At least 55 records · Page 3Linked to original sources
PubMed1979

Electron probe microanalysis of elemental composition of mouse cardiac myocytes during post-natal maturation.

Elemental concentrations in the cytoplasm and nucleus of t tests post-natal mouse myocytes were measured at 2, 4, 8, 16, 32 days and in adults using electron probe X-ray microanalysis. Using an analysis of variance test, significant age dependent changes were found in intracellular potassium, sulfur, phosphorus, and chlorine concentrations (mg/kg dry weight), while sodium and magnesium concentrations did not show significant changes. The application of t tests following linear regression analyses (age versus concentration for each element) did, however, give a significant slope for cytoplasmic sodium, potassium, sulfur, and phosphorus values. The findings correspond closely with an emission spectroscopy-titrimetric study of whole heart ventricle of the same developmental period (Hazelwood and Nichols, '70).

Aging↗
PubMed1991

Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors.

Honey bee photoreceptors contain large sacs of endoplasmic reticulum (ER) that can be located unequivocally in freeze-dried cryosections. The elemental composition of the ER was determined by electron probe x-ray microanalysis and was visualized in high-resolution x-ray maps. In the ER of dark-adapted photoreceptors, the Ca concentration was 47.5 +/- 1.1 mmol/kg (dry weight) (mean +/- SEM). During a 3-sec nonsaturating light stimulus, approximately 50% of the Ca content was released from the ER. Light stimulation also caused a highly significant increase in the Mg content of the ER; the ratio of Mg uptake to Ca released was approximately 0.7. Our results show unambiguously that the ER is the source of Ca2+ release during cell stimulation and suggest that Mg2+ can nearly balance the charge movement of Ca2+.

Animals↗
PubMed1989

[Comparative study of bioactive calcium phosphate ceramics after implantation in spongy bone in dogs. Histologic, ultrastructural and electron probe microanalysis].

An experimental model of posterior spine arthrodesis in dogs was created using 3 types of calcium phosphate biomaterials already known for their applications as bone substitutes, namely: hydroxyapatite (HA), which is not readily resorbable; highly resorbable tricalcium phosphate (TCP); and a mixture of HA and TCP (BCP), the resorbability of which depends on the proportion of HA and TCP. The BCP implants had a macroporous structure, whilst the HA and TCP implants were used in dense form. The creation of macropores increases the surface exchange area, thus enabling the osseous colonization processes. By carefully removing the posterior articular facets it was possible to remove the articular surfaces and to fit into each appropriate location a block a few millimeters in diameter. The anatomopathological assessment was performed using histological methods, transmission electron microscopy, and energy dispersion microprobe analysis. Our results indicate that calcium phosphate ceramics may be used as bone substitutes for carrying out arthrodeses, provided (1) immediate immobilization using a spine containment technique is effected; (2) their chemical composition is sufficiently stable over time; (3) they are sufficiently bioactive so as to allow their colonization and replacement by bone.

Animals↗
PubMed1989

31P-NMR study of P-based dental adhesives and electron probe microanalysis of simulated interfaces with dentin.

The structure and function of P in P-based dental adhesives have not been defined properly. The purpose of this study was to evaluate these parameters in some currently available materials. Five dental adhesives were selected: Bondlite, Clearfil New Bond, J&J Dental Adhesive, Prisma Universal Bond, and Scotchbond. High-resolution 31P-NMR spectroscopy was used to identify the phases of the incorporated P and the kinetics of monomer-bonded P in an aqueous environment. Areas of 5 mm diameter located on polished sound dentin were subjected to the corresponding adhesive treatments and covered with translucent molds of the same diameter, which were filled up to 1 mm length with a visible-light-cured hybrid composite. Following 60 sec of light exposure from lateral directions, the specimens were embedded in fast-setting resin, cross-sectioned, and analyzed in an electron probe microanalyzer. The elemental profiles of Ca, P, and Cl were determined from area and line scans. Great differences in the 31P resonance shifts were obtained from the tested adhesives, indicating the presence of monomer-bonded and free P. A rapid hydrolysis of the resin-bonded P in the presence of water was identified. The x-ray images revealed dentin demineralization, with distinct differences in the P distribution pattern and the P/Cl ratio.

Dental Bonding↗
PubMed1978

Electron probe microanalysis of fluorotic bovine teeth.

Incisor teeth were obtained from adult cattle which since 4 months of age to 5 or 6 years were maintained on rations containing a yearly average of 40 ppm F in the forage. Microchemical analyses were performed on the fluorotic bovine incisors. The microdistribution of fluoride varied markedly at different sites within the same tooth. Fluoride concentrations varied with the depth from the tooth surface and were influenced by the concentrations of fluoride present in the forage during amelogenesis, and the presence of hypoplastic pits and hyperplastic coronal cementum in enamel. The cementum in these lesions contained remarkably high concentrations of fluoride, and it was less calcified and more porous than adjacent enamel.

Animals↗
PubMed1991

[Electron probe microanalysis of fluorine content in deciduous and permanent teeth from an area with a fluoride-deficient (0,3% mg/I) water supply].

The content of fluorine in deciduous and permanent teeth of young people was determined by x-ray microanalysis. The purpose of this investigation was to determine the concentrations of F in teeth without any supplementation of fluorides and to elaborate basic dates as a standard of comparison. F was measured in microvolumes with a wavelength-dispersive spectrometer (Step-Scan 100 sec) after coating with about 300 A of Carbon. The highest values were established in the outermost surface of enamel with quantities between 300 and 600 micrograms/g. The lower concentrations were found in deciduouns teeth. In both dentitions the F-content increases at the surface following the permanent change between de- and remineralization. In subsurface areas the values are decreasing quickly. At a deep of 10 microns from surface layer the content is only 70 micrograms/g and than it declines to a minimum of 20-30 micrograms/g.

Child↗
PubMed1975

Electron probe microanalysis of secondary carious lesions associated with silver amalgam fillings.

Secondary caries associated with silver amalgam fillings is characterized by outer lesions and cavity wall lesions. In this study the content of minerals and the penetration of elements from the amalgam into such lesions were analyzed. In sections of 11 teeth including cases of natural secondary caries and experimental in vitro and in vivo lesions around silver amalgam fillings the distribution of Ca, P, Mg, Zn, Sn, Cu, Ag and Hg was studied by means of two-dimensional X-ray images, linear scans and point analyses. Dentine wall lesions where microradiographs had shown increased radiopacity relative to intact tissue, exhibited considerably reduced Ca and P values. The outer portion of the radiopaque areas contained 5--8% Zn and Sn, decreasing to less than 0.1% at a varying distance up to 130 mum from the cavity wall. Hg was not detected, nor was Ag, except in one specimen. The increased radiopacity of this zone as observed on microradiographs is, therefore, obviously caused by the presence of Zn and Sn. Zn and Sn had also penetrated into the moderately demineralized enamel lesions, but the concentrations were generally lower than those observed in the dentine.

Calcium↗
PubMed1976

Electron probe microanalysis of secondary carious lesions adjacent to silicate fillings.

Secondary caries associated with silicate fillings is characterized by lesions at the tooth surface and lesions of the cavity wall. The mineral content of the cavity wall lesions and the penetration of elements originating from the silicate fillings were studied in experimental in vitro and in vivo lesions as well as in natural carious lesions. Dentine wall lesions, where microradiographs had shown increased radiopacity relative to intact tissue, exhibited increased Ca and P values. Elements derived from the silicate fillings were regularly found in enamel and dentine. The concentrations of fluorine (F) and of zinc (Zn) amounted to 2-3% by weight close to the cavity wall and decreased gradually to less than 0.1% at depths of 600 mum and 400 mum, respectively, from the cavity. Aluminum (Al) most often occurred in a 20-40 mum-wide zone, showing a maximum concentration of 2-3% near the cavity. Sulfur (S) was often present in the dentinal cavity walls of natural secondary caries, but not in the in vitro specimens. The findings indicate that F released from the silicate filling significantly modifies the progress of a carious lesion in the adjacent enamel and dentine. Through its tendency to form complexes with F, Al may possibly enhance the cariostatic effect of F.

Aluminum↗
PubMed1991

Three-dimensional spatial relationship between the collagen fibrils and the inorganic calcium phosphate crystals of pickerel (Americanus americanus) and herring (Clupea harengus) bone.

High-voltage (1.0 MV) electron microscopy and stereomicroscopy, electron probe microanalysis, electron diffraction and three-dimensional computer reconstruction, have been used to examine the spatial relationship between the inorganic crystals of calcium phosphate and the collagen fibrils of pickerel and herring bone. High-voltage stereo electron-micrographs were obtained of cross-sections of the cylinder-shaped intramuscular bones in uncalcified regions, in regions where only one or only several crystals had been deposited in some of the fibrils, and in successive sections containing progressively more mineral crystals until the stage of full mineralization was reached. High-resolution electron probe microanalysis confirmed that the electron-dense particles contained calcium and phosphorus. In the earliest stages of mineralization and progressing throughout the mineralization process, the crystals are located only within the collagen fibrils; crystals are not observed free in the extracellular spaces between collagen fibrils. The progressive increase in the mass of mineral deposited in the bone tissue with time occurs, essentially, completely within the collagen fibrils including the stage of full mineralization. At this stage, cross-sectional profiles of collagen fibrils are completely obliterated by mineral. A small number of crystals that are located on or close to the surface of the fibrils appear to extend a very short distance into the spaces between the fibrils. These ultrastructural observations of the very onset of calcification in which nucleation of the calcium phosphate crystals is clearly shown to begin within specific volumes of collagen fibrils, and of the subsequent temporal and spatial sequences of this phenomenon, which shows that calcification continues wholly within the collagen fibrils until maximum calcification is achieved, add important information on the basic physical chemical mechanism of the calcification and the structural elements that are involved. The spatial and temporal independence of the sites where mineralization is initiated establishes that such ultrastructural locations within individual collagen fibrils represent independent, physical chemical nucleation loci. The findings are totally inconsistent with the proposal that crystals must first be deposited in matrix vesicles, or other components such as mitochondria, and subsequently released and propagated in the interfibrillar space, until they eventually reach and impregnate the hole zone regions of the collagen fibrils. Three-dimensional computer reconstruction of serial transverse and longitudinal sections demonstrates periodic swellings along the collagen fibrils, corresponding to the hole zone region of their axial period as mineralization proceeds.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Visualization of sulfur-containing components associated with proliferating chondrocytes from rat epiphyseal growth plate cartilage: possible proteoglycan and collagen co-migration.

Electron microscopy of epiphyseal growth plate cartilage from normal 4-5-week-old rats has revealed extensive fibrillar aggregates and globules in the pericellular spaces of proliferating chondrocytes. These cells contained small globules and diffusely coiled, fine filaments located within large, membrane-invested vacuoles. All such structures were observed after a variety of different tissue fixation regimes, including glutaraldehyde, osmium tetroxide, and potassium pyroantimonate. The fibrillar aggregates and globules were often overlapping and intermeshed and extended to 0.5 micron in length from their point of origin at cell membranes. Vacuoles were usually found at the periphery of cells, and some, by membrane fusion with the cell envelope, appeared contiguous with extracellular spaces wherein their contents could be discharged. Fine filaments and globules were occasionally observed in the Golgi complex and cisternae of endoplasmic reticulum of the chondrocytes. Further characterization of the cellular and pericellular components by electron microscopic radioautography, electron probe microanalysis, and electron spectroscopic imaging indicated the presence of sulfur, a result suggesting these aggregates, filaments, and globules in part represent proteoglycans in various stages of synthesis, secretion, and assembly. Additional radioautography utilizing 3H-proline implied that filament bundles are also composed of collagen, a result posing the possibility that this protein and the putative proteoglycans may co-migrate both intracellularly and within pericellular matrices. In extracellular matrices adjacent to cell lacunae, the fibrillar aggregates appeared in close association with typical collagen type II fibrils, an observation providing evidence for proteoglycan-collagen network formation in this region of the rat epiphysis. These microscopic and analytical data in situ would support certain studies in vitro of proteoglycan-collagen type II and IX association and are important in describing the interaction of such cartilage components ultimately involved in matrix formation.

Animals↗
PubMed1977

Crystalloid nature of mineral deposits in Bowman's capsule of the human glomerulus. Study by X-ray microanalysis and electron microdiffraction.

Abnormal crystalline mineral deposits are often observed in the basement membrane of Bowman's capsule in the human glomerulus. The nature of these deposits has been the subject of much discussion. By means of electron probe microanalysis and electron diffraction techniques, we have identified these abnormal deposits as whitlockite (beta-calcium-orthophosphate).

Calcium Phosphates↗
PubMed1989

Subcellular calcium content in cardiomyopathic hamster hearts in vivo: an electron probe study.

In the Syrian cardiomyopathic hamster heart, abnormal cellular calcium regulation, resulting in cellular calcium overload, is believed to play a role in the pathogenesis of cardiac hypertrophy and failure. Alternatively, the primary abnormality may be coronary vasospasm, resulting in reperfusion-induced necrosis. According to the latter hypothesis, only those cells that suffer an ischemic insult would contain elevated calcium levels. To determine whether a generalized elevation in myocytic calcium exists in myopathic hamster hearts, we measured cellular and subcellular calcium concentrations by electron probe microanalysis in cryosections of 50-day and 96-day myopathic and control hearts, rapidly frozen in vivo. Total calcium content of ventricular homogenates from each group was also measured by atomic absorption spectrophotometry. No significant differences in subcellular calcium were found by electron probe microanalysis among 50-day and 96-day myopathics and their age-matched controls. In 50-day myopathic and control hearts, mitochondrial calcium was 0.7 +/- 0.2 and 0.9 +/- 0.2, respectively, and A-band calcium was 3.0 +/- 0.4 and 2.6 +/- 0.4 mmol calcium/kg dry wt(+/- SEM). Results from 96-day animals were similar. Localized regions of elevated calcium were found only at sites of necrotic foci: in Na+-loaded cells (mitochondria: 4.7 +/- 1.3 (SEM) mmol/kg dry wt), in dying cells (mitochondria: 72 +/- 22 (SEM) mmol/kg dry wt) or as extracellular deposits (7-10 mol/kg dry wt). Total calcium content of hearts from myopathic hamsters, as determined by atomic absorption spectrophotometry, was also 13 times (50-day) and 50 times (96-day) higher than controls. These results demonstrate that there is a marked heterogeneity in cellular calcium content in myopathic hamster hearts, but the data do not support the hypothesis of a generalized cellular calcium overload.

Animals↗