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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↗
PubMed1980

Electron-probe microanalysis. Aid in the study of skin granulomas.

Several causes of noncaseating epithelioid granulomas of the skin must be considered before the diagnosis of sarcoidosis can be made. We report here three such cases that were studied retrospectively with scanning electron microscopy in combination with backscattered electron imaging and x-ray energy spectrometry. Inorganic particles were identified in the granulomas of two patients, illustrating that these techniques are valuable aids in establishing the cause of granulomas.

Adult↗
PubMed1993

Strontium, a tracer to study the transport of calcium in mineralizing tissues by electron probe microanalysis.

In growth plate cartilage the mineralization starts extracellularly in the lower hypertrophic zone. The mineral formed is the calcium phosphate apatite. Enough calcium and phosphate must be available at the mineralization front as well as in regions with proceeding mineralization. There must be a transport of Ca (and phosphate) to these sites. Electron probe X-ray microanalysis is a well established method to analyze element concentrations in small volumes, but it cannot discriminate isotopes. Strontium is similar to Ca in its chemical and biological behaviour and is therefore a suitable tracer to investigate the transport of Ca. Small amounts of Sr (0.1 g per kg body weight) were administered intraperitoneally to young rats. After definite intervals of time ranging from 10 to 120 min, 2-4 rats were killed. On freeze dried cryosections the Sr/Ca ratio of the serum and of the intra- and extracellular space of the growth plate were measured. The Sr/Ca ratio reaches its maximum after about 10 min in the serum and after 20 min in the extracellular space of growth plate cartilage. The intracellular Sr/Ca ratio shows large variations because of the low intracellular Ca and Sr concentration, and is lower than the extracellular ratio for times shorter than 30 min. No significant differences were found between the different cell zones of the unmineralized growth plate cartilage. The results demonstrate that the transport of Ca to the growth plate cartilage is relatively fast and that in growth plate cartilage, Ca is transported extracellularly, not intracellularly.

Animals↗
PubMed1993

[Corrosive changes of dental alloys in oral environment--scanning electron microscopic observation and electron probe microanalysis on crown surfaces].

In order to study the changes of the intraoral metals, the surface condition and composition of the crowns removed from mouths were analyzed by SEM and EPMA. Thirty-four samples were categorized into four types of alloys. Corrosive changes were evaluated by comparing the analysis results between the crown surface and its fresh sectioned surface, and also with the data from former studies. 1. Changes observed in the Au alloys were slight compared to the other three types, both in surface feature and composition, except for a slight decrease in Cu. 2. In some Au-Ag-Pd alloys, nearly no dissolution was evident. Composition changes were small, with a slight decrease in Ag and relative increase in Pd. 3. The greatest changes were observed in the Ag-Sn-Zn alloys and Ag-In alloys, even with short intraoral usage period. Generally, their surfaces were rough, with thick layers of organic materials. The dendritic structure was distinct, and dissolution between each dendrite was observed. 4. Many of the Ni-Cr alloys presented dendritic structure with dissolution. Decrease in Ni and relative increase in Si and Cr were observed. 5. Corrosive changes showed a close resemblance to the results obtained by the conventional basic tests. However, there were some features which did not coincide, depending on the types of alloys.

Corrosion↗
PubMed1980

Cryoultramicrotomy, electron probe microanalysis and STEM of myocardial tissue.

Heart muscle preparations (papillary muscles and trabeculae) were frozen at 4.2 K on metal plate under vaccum after their length-tension relationships showed that no damage had occurred during dissecting and mounting the strips on the holder. Freeze substitution of some preparations directly after freezing demonstrated that no important cell damage due to ice crystals occurred in superficial cell layers during freezing. Ultrathin cryosections obtained at -130 degrees C were freeze dried and analyzed, in the STEM mode. The better the freezing procedure, the poorer was the contrast of the sections under electron microscopy. Preliminary approaches to increasing contrast after sublimation of tissue water show that a small increase in contrast is generally obtained at the cost of the peak/background ratio due to pronounced mass loss. The results of our analyses show that C1 content in heart muscle cells is high and distributed throughout the cytoplasm. Ca is detectable and quantitable in resting muscle in SR cisternae. The Ca amount in cytoplasm is low and just at the limit of detectability under our current analysis conditions. Preliminary experiments on papillary muscles subjected to caffeine contracture showed that calcium is not detectable in the cisternae as is the case in control experiments. Only a moderate amount of Ca is detectable in mitochondria, whereas the concentrations in cytoplasm, as in resting cardiac muscle, is too low to be quantitated.

Animals↗
PubMed1980

Electron probe microanalysis of isolated brain capillaries poisoned with lead.

The blood-brain barrier has been proposed as an important site for the toxic action of lead in the central nervous system. To investigate this, capillary endothelial cells were isolated from rat cortex and exposed to lead in vitro. Tissue suspensions were then prepared for electron microscopy and X-ray microprobe analysis. In cells exposed in vitro to lead, electron-dense deposits were observed within mitochondria. With X-ray analysis, it was determined that these intramitochondrial deposits contained lead in a non-crystalline matrix. Also, lead appeared to be accumulated in the same intramitochondrial areas as calcium. The results suggest that lead is preferentially sequestered in mitochondria of capillary endothelial cells. Further, this selective localization may be associated with lead-induced disruptions in intracellular calcium metabolism and transepithelial transport processes.

Animals↗
PubMed1982

Mineralization of human aortas with coarctation: quantitative electron probe microanalysis.

Aortas with coarctation (isthmus stenosis) are obviously an ideal model to investigate pressure dependent changes of the aorta, as one can compare the proximal region (high pressure) with the distal region (low pressure). 7 aortas of patients aged from 2 months to 54 years were investigated. The concentrations of Na, Mg, P, S, C1, K, and Ca were determined by electronprobe microanalysis. Ca and P are constituent parts of the developing mineral and are mainly discussed. The Ca/P ratio (by weight) is about 0.3 in the unmineralized and about 2 in the mineralized tissue. Mineralization is demonstrated by a parallel increase of Ca, P, and the Ca/P ratio. Enrichments of Ca and P are found above all in a subintimal band. Usually they occur proximally and distally, but are much more pronounced proximally. Even in the aorta of a 2 month old infant enrichments were found proximally, but not distally. Thus mineral deposits occur very early in regions of hypertension. The differences between the proximal and distal region may demonstrate the influence of blood pressure on vascular mineralization. The mineralization starts in small compartments, which increase in size and number in the process of mineralization. Mineralized regions could often be localized by cathodoluminescence. But to demonstrate and localize the initial mineral deposits and to quantify element contents, electronprobe microanalysis became indispensable.

Adolescent↗
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↗