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At least 1,423 records · Page 79Linked to original sources
PubMed2004

Physical and chemical characterization of mn phosphate/sulfate mixture used in an inhalation toxicology study.

The use of methylcyclopentadienyl manganese tricarbonyl (MMT) in unleaded gasoline has given rise to numerous debates on the potential public health risk associated with manganese emissions. In fact, combustion products are mainly Mn phosphate, Mn sulfate, and Mn phosphate/sulfate mixture. Our research group did several inhalation studies in order to assess the toxicity of each Mn species. The objective of this study is to determine the physical and the chemical characteristics of a mixture of Mn phosphate/sulfate used in one of these inhalation toxicology studies. First, the mixture was analyzed by X-ray diffraction in order to obtain the specific peak of Mn phosphate and Mn sulfate. These peaks were used as reference. Second, samples of the mixture were collected on filters in the inhalation chamber at a concentration level of 3000 microg/m(3). They were analyzed by scanning electron microscopy (SEM), analytical transmission electron microscopy (ATEM), and x-ray energy-dispersive spectrometry (EDS) to show their size, morphology, and chemical composition. Results indicate that 33% of the particles were found to be agglomerated, while free particles accounted for 44% for Mn phosphate and 23% for Mn sulfate.

Electron Probe Microanalysis↗
PubMedDate not supplied

Simultaneous triple fluorescence detection of mRNA localization, nuclear DNA, and apoptosis in cultured cells using confocal scanning laser microscopy.

We describe a multifluorescence labeling technique for simultaneous detection of mRNA, nuclear DNA, and apoptosis in cultured cells. Digoxigenin-labeled cRNA probes were used to study proto-oncogene expression in rat pleural mesothelial cells undergoing apoptosis following exposure to crocidolite asbestos or hydrogen peroxide (H2O2). Hybridized cRNA probe was detected by immunolocalization with an anti-digoxigenin monoclonal primary and fluorophore-conjugated anti-mouse secondary antibody. Cells undergoing apoptosis were simultaneously identified by the TdT-mediated biotin-dUTP nick-end labeling (TUNEL) method and a streptavidin-conjugated far-red fluorophore, and nuclear DNA was stained with oxazole yellow dimer (YOYO-1). With confocal scanning laser microscopy, we demonstrated increased c-jun mRNA expression within the cytoplasm of both TUNEL-positive and non-apoptotic cells following exposure to either crocidolite asbestos or H2O2. Thus, this technique represents a useful in vivo approach for evaluating apoptosis-associated gene expression with confocal scanning laser microscopy.

Animals↗
PubMed1994

Intercellular contacts between chick stereocilia after acoustic overstimulation.

The goal of this study was to analyze the distribution of actin and the shape of stereocilia of chick hair cells that survive acoustic trauma. Chicks were exposed to intense octave band noise for 4 h. They were killed either immediately after the exposure, after 6 or after 72 h. The basilar papillae were examined using scanning electron microscopy and fluorescence microscopy, with phalloidin as an actin-specific probe. Injured hair cells which survived the trauma displayed disorganized stereocilia bundles, elongated stereocilia, and supernumerary stereocilia bundles. Tips of stereocilia in the damaged region of the basilar papilla appeared to be in contact with tips of stereocilia of neighboring hair cells. These contacts may represent 'stress links' which appear in traumatized hair cells. These results show that substantial changes in stereocilia occur within hours of exposure to intense noise. We speculate that surviving hair cells may play a role in the process of repair of the basilar papilla after noise trauma and that the changes in stereocilia structure described here are related to this role.

Acoustic Stimulation↗
PubMedDate not supplied

[Scanning electron microscopy and elementary analytic studies of osteosarcoma].

By scanning electron microscopical (SEM) screening analyses of 14 osteosarcomas characteristic three-dimensional structures of tumor osteoid could be demonstrated. These osteoid formations are highly characteristic for osteosarcoma; we did not find them at any other bone tumor or tumor like lesion until now. With these results a better understanding of characteristic growth patterns of bone tumors could be achieved by SEM. No specific results could be found by elementar analysis, x-ray microanalysis, x-ray fluorescence and x-ray diffractometer techniques. The significance of single interesting values has to be evaluated in the future.

Bone Neoplasms↗
PubMed1998

Desktop X-ray microscopy and microtomography.

Recent developments in X-ray microtomography have made it possible to miniaturize a CT scanner into a versatile and cost-effective desktop system that fits into any laboratory environment. The possibilities of the technique are demonstrated for a range of applications. It is also shown how an existing scanning electron microscope with an X-ray detector can, with a specially developed attachment, be transformed into an X-ray microscope and microtomograph.

Animals↗
PubMed2004

The use of scanning ion conductance microscopy to image A6 cells.

BACKGROUND: Continuous high spatial resolution observations of living A6 cells would greatly aid the elucidation of the relationship between structure and function and facilitate the study of major physiological processes such as the mechanism of action of aldosterone. Unfortunately, observing the micro-structural and functional changes in the membrane of living cells is still a formidable challenge for a microscopist. METHOD: Scanning ion conductance microscopy (SICM), which uses a glass nanopipette as a sensitive probe, has been shown to be suitable for imaging non-conducting surfaces bathed in electrolytes. A specialized version of this microscopy has been developed by our group and has been applied to image live cells at high-resolution for the first time. This method can also be used in conjunction with patch clamping to study both anatomy and function and identify ion channels in single cells. RESULTS: This new microscopy provides high-resolution images of living renal cells which are comparable with those obtained by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Continuous 24h observations under normal physiological conditions showed how A6 kidney epithelial cells changed their height, volume, and reshaped their borders. The changes in cell area correlated with the density of microvilli on the surface. Surface microvilli density ranged from 0.5 microm(-2) for extended cells to 2.5 microm(2) for shrunk cells. Patch clamping of individual cells enabled anatomy and function to be correlated. CONCLUSIONS: Scanning ion conductance microscopy provides unique information about living cells that helps to understand cellular function. It has the potential to become a powerful tool for research on living renal cells.

Animals↗
PubMed1994

Study on gutta-percha points using scanning electron microscopy and analysis with electron microprobe.

A comparative study of the apical morphology and contour was performed with the scanning electron microscope at 45x, 70x and 300x, while the chemical composition of eight gutta-percha point brands was surveyed with an EDAX 9100 electron microprobe. They were classified according to their apical morphology as conical (25%) and truncate (75%), based on their contour as regular (50%) and irregular (50%) and according to their surface as without defects (50%) and with defects (50%). The analysis of inorganic compounds revealed the presence of varying proportions of Zn, Ba, Si, Mg. Ca, P, Cl and Al, possibly implying that the presence of Ba and Al could interfere with postendodontic repair or at least irritate the periapical area if inadvertently overfilled.

Electron Probe Microanalysis↗
PubMed1989

A minibead method for detection of membrane lectins.

Membrane lectins are being increasingly implicated in many biological phenomena. Previous methods for detection of these substances are applicable only to homogeneous cell populations. We have now developed a method that permits morphological identification of lectin-bearing cells in heterogeneous cell populations. Amide-modified latex minibeads (0.345 or 0.532 micron) were activated with glutaraldehyde and then covalently bound to p-aminophenyl derivatives of various sugars. When the probe thus constructed was incubated with cell systems known to bear well-defined membrane lectins (galactosyl receptors in hepatocytes, mannosyl receptors in macrophages), binding occurred and could be visualized by scanning electron microscopy. Binding was inhibited in the presence of excess soluble sugar, indicating the specificity of reaction. Incubation of a mixture of two different-sized probes with two different cell types led to segregation of the probes. This method also permits semiquantification of binding.

Animals↗
PubMed1994

Calcium fluoride formation on sound enamel using fluoride solutions with and without lactate.

The formation of calcium (Ca) fluoride (CaF2) on bovine enamel blocks during clinically relevant treatment times using neutral fluoride (F) solutions (0.26 mol/l F) with and without 0.1 mol/l lactate was investigated. Uncoated and pellicle-coated blocks were evaluated for alkali-soluble (1 mol/l KOH, three consecutive 24-hour treatments) Ca, PO4, and F after treatment by the F solutions for 0, 5, 15, 30, and 60 min. There was an overall time-related increase in F recovery, while Ca tended to remain at baseline levels. Less F was recovered from the pellicle-coated blocks. The addition of lactate to the F treatment solution did not result in an overall increase in alkali-soluble F recovery, but did result in the formation of cuboidal shaped crystals which closely approached the morphology of pure CaF2. A 1:2 stoichiometric ratio Ca:2F (mol:mol) was not established based on chemical analyses. The ultrastructural and elemental composition of surface deposits on the samples, as determined using scanning electron microscopy, X-ray diffraction, and energy-dispersive spectroscopy, established the presence of CaF2 after 24-hour F treatments; however, it was not possible to directly demonstrate the formation of CaF2 after clinically relevant treatment times.

Animals↗
PubMed1999

[The fine fraction of airborne particulate: a pollutant of increasing environmental and health relevance. Methodologies for sampling and characterizing single particles].

Among the atmospheric pollutants detectable in the environment, the inhalable airborne particulate (PM10) is regarded with increasing care. Indeed a number of epidemiological studies support the correlation between both acute and chronic adverse health effects and the PM10 pollution in the urban environment. According to recent results the health effects could be related to the physico-chemical characteristics of the particulate itself. With the aim of characterising the individual particles, PM10 samples collected by multi-stage cascade impactor are examined by scanning electron microscopy (SEM) and X-ray microanalysis with energy dispersion spectroscopy (EDS). The obtained data are analysed using multivariate statistical techniques (hierarchical clustering methods, principal factor analysis) to determine the components of the particulate. By these methods a series of studies was carried out by the Istituto Superiore di Sanità to investigate the PM10 pollution in several environmental situations.

Air Pollutants↗
PubMed1997

Digalactosyl diacylglycerols, plant glycolipids rarely found in bacteria, are major membrane components of bacteroid forms of Bradyrhizobium japonicum.

The membrane lipids of free living and bacteroid forms of Bradyrhizobium japonicum, obtained from nodules occupied by both typed and untyped bacteria, were isolated and characterized by a combination of NMR spectroscopy, mass spectrometry, and other chemical and physical methods. These studies indicated that both the free living and bacteroid forms of this organism contain glycolipids almost exclusively of the type found in plant cells. In the bacteroid forms, there was a dramatic shift towards the synthesis of digalactosyl diacylglycerol as the major lipid. This glycolipid has rarely been found outside of the plant kingdom and photosynthetic bacteria, and its occurrence in the bacteroid form of a plant symbiont is therefore remarkable. The presence of plant cell and organelle contaminants in the bacteroid preparations was ruled out by scanning electron microscopy, Southern blot analyses for plant DNA using specific gene probes, and chemical analyses for plant marker steroids, steroid glycosides, and cerebrosides. Digalactosyl diacylglycerol is not found in the plasma membrane of plant cells (of which the peribacteroid membrane is an extension) but is thought to be restricted to plastids. This result follows our earlier finding that the other predominant plant glycolipid, sulfoquinivosyl diacylglycerol, is a membrane component of fast growing Rhizobia and is found even when cells are cultivated in free culture where there is no question of plant contamination. The near absence of these lipids in the membranes of bacteria outside of this special group of organisms and photosynthetic bacteria suggests that the trait could have been passed on through gene transfer from plants to the bacteria at some point during the development of their symbiotic relationship. In the case of digalactosyl diacylglycerol, there is also the possibility that some common biosynthetic intermediates are used by both the plant and the bacteria. This is a striking parallel with some host-pathogen interactions.

Carbohydrate Conformation↗
PubMedDate not supplied

Functionally gradient bonelike hydroxyapatite coating on a titanium metal substrate created by a discharging method in HBSS without organic molecules.

PURPOSE: This study evaluated the quality of coatings on titanium surfaces prepared by discharging in Hanks' balanced salt solution without organic molecules (HBSS-). MATERIALS AND METHODS: 10 x 10 x 1.0-mm titanium plates were used as cathodes of a coating device developed in the laboratory and immersed in HBSS-. A piece of platinum foil was used as a counterelectrode. Discharging was maintained at 1 A and 10 V (416 mA/cm2) for periods of 90, 270, and 540 seconds. Crystal phases of the coatings were identified by x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). In addition, the surface characterization and Ca/P atomic ratio of the titanium surfaces were determined by x-ray photoelectron spectroscopy (XPS). Furthermore, the surface topography, the thickness of the coatings, and the bonds between coatings and titanium substrates were observed by scanning electron microscopy. RESULTS: The FTIR and XRD studies demonstrated that the deposits on the titanium after 540 seconds of discharging were crystalline hydroxyapatite. In addition, the thickness of the titanium suboxide layer increased during discharging. The XPS studies indicated that after 540 seconds of processing, the mean Ca/P ratio of the coatings on the titanium was 1.71, which is similar to that of human bone. DISCUSSION: In addition, the replacement of sodium ions with calcium ions seemed important for the promotion of crystallization of the coating. Furthermore, the XPS studies demonstrated that the coatings had a gradient function. Scanning electron microscopy showed that adhesion between coatings and the titanium substrate was close. The coatings were approximately 1 microm thick. CONCLUSION: These findings suggest that a very thin crystalline bonelike hydroxyapatite coating with a gradient function could be prepared on a titanium metal substrate in HBSS- by a discharging method.

Adhesiveness↗
PubMed1998

Identification of zinc phosphide in a falsely labeled rodenticide bait.

"Kela" is a commercial rodenticide bait commonly used in Israel, made of wheat grains, which, according to its label, contains chlorophacinone. This product was involved in the death case of a man in which the victim's female companion was accused of assisting in this suicide and was subsequently convicted. Analysis of the wheat grains revealed zinc phosphide, whose use is restricted to authorized exterminators only, instead of chlorophacinone. Zinc phosphide was identified using microscopic examination, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray powder diffraction (XRD).

Aged↗
PubMed1984

Varied light and scanning electron microscopic appearances of barium sulphate in smears and histological sections.

The various light and scanning electron microscopic appearances of barium sulphate in smears and in histopathological lesions in sections are illustrated. One type of barium sulphate (E-Z-HD) includes much larger, bright birefringent particles and has very different appearances from other widely used types. Such larger particles in sections were not originally suspected to be barium sulphate and were identified only by energy dispersive x ray analysis in a scanning electron microscope. This form of barium sulphate is used for double contrast upper gastrointestinal radiography, and is not thought to have been responsible for the lesions in which it has been observed by us.

Barium Sulfate↗
PubMed1987

Image analysis and X-ray microanalysis in cytochemistry.

When cytochemical reaction products are homogeneously distributed within an organelle, point analyses suffice for the quantitative approach. However, quantitative analysis becomes tedious, when the elements in the reaction product are inhomogeneously distributed. Problems arise when elements from two reaction products have to be related to each other, or to endogenous cytological products (ferritin, haemosiderin, calcium, electron dense markers), either topographically or in concentration. When analyzing inhomogeneous/heteromorphical reaction product-containing organelles special attention has to be paid to measure and relate both volume and concentration. In this paper a relative simple structure (eosinophil granules) is chosen to demonstrate that the acquisition of the requested morphometrical plus chemical information and their integration is possible. The following points will be covered to acquire the morphometrical and chemical information: a). How to estimate the total cell cross-sectioned area. b). How to estimate the total cross-sectioned area of all reaction product-containing particles inside that cell. The ratio of these two areas will provide the requested information about the particle volume fraction. By using the X-ray detector in addition: c). How to acquire the chemical information at the requested resolution, within a reasonable total acquisition time d). How to integrate the morphometrical and chemical data per organelle, by matrix analysis in a reduced scan area. e). How to acquire quantitative chemical information, by the use of cross-sectioned standards. f). How to make this acquisition method independent from changes in the instrumental conditions during the acquisition.

Animals↗
PubMed2005

Particulate matter characterization at a coastal site in south-eastern Italy.

Several samples of airborne particulate matter (PM), collected from 6th November to 6th December 2003 at a coastal site in the south-east of Italy, have been analyzed by different techniques to characterize elemental composition and morphological properties of the inorganic PM fraction and obtain preliminary results on anthropogenic contributions. Al, Cr, Cu, Fe, Mn, V, Pb, Ti, Ca and Zn mass concentrations, evaluated by an inductively coupled plasma atomic emission spectrometer, account for up to l% of the bulk PM mass in the investigated samples. According to geochemical calculations, Ca, Al, Fe and Mn are predominantly of crustal origin, while Cr, Cu, Pb, V, Ti and Zn heavy metals are of anthropogenic origin. Ion chromatography analyses have identified sulfate (SO(4)(2-)) nitrate (NO(3)(-)), sodium (Na(+)), and ammonium (NH(4)(+)) as the main ionic components accounting for up to 38% of the total PM mass and up to 90% of the total ionic mass. Besides ion chromatography, X-ray energy dispersive (EDX) microanalyses have revealed the high variability of Cl: its weight concentration varies from about 24% to below the detection limit (>or=0.5%) in the investigated samples. The marked anti-correlation between the excess of S and the Cl/Na ratio has allowed inferring that reactions between sea salt particles and acidic sulfates, which liberate HCl gas to the atmosphere leaving particles enriched in non-sea-salt sulfates, have significantly contributed to chloride depletion. Morphological analyses by scanning electron microscopy have shown that about 90% of the total sampled particles have a diameter <or=5 microm.

Air Pollutants↗
PubMed1994

Protoporphyrin biosynthesis in melanoma B16 cells stimulated by 5-aminolevulinic acid and chemical inducers: characterization of photodynamic inactivation.

The stimulation of protoporphyrin (PP) biosynthesis in B16 melanoma cells in order to facilitate photodynamic cell killing was studied. Biosynthesis and accumulation of PP in the melanoma cells was increased from 8 to 15 pmol/mg protein by the use of dimethyl-sulfoxide (DMSO), a differentiation-inducer. Treatment of the cells with the porphyrogenic agent allylisopropyl-acetamide (AIA) stimulated an additional PP increase. The most remarkable enhancement of intracellular PP was achieved by the supplementation of 5-aminolevulinic acid (5-ALA) to the growth medium following the addition of DMSO and AIA during the induction phase. The intracellular concentration of PP exceeded 21,950 pmol/mg protein following combined stimulation by DMSO/AIA and 5-ALA. The porphyrins produced in the incubated cells, in serum-depleted medium, consisted of 95% PP; 88% of it was recovered from the cells and only 7% was excreted into the medium. Photosensitization of the B16 melanoma cells containing high PP concentrations was effective even at low light doses. Potassium (K) efflux was the first measurable sign of cell damage determined by X-ray microanalysis (XRMA) following fast liquid-nitrogen fixation. During a 1 min interval, 70% of cellular K was lost. After 5 min illumination, complete cell destruction was detected by scanning electron microscopy (SEM) and XRMA. The photodamaged cells showed influx of Na, Cl and Ca ions accompanying the immediate K losses. Ultrastructural cell damage was manifested by disintegration of the outer membrane. Total cell death of B16 melanoma cells was achieved by chemical induction of endogenous PP and photosensitization.

Allylisopropylacetamide↗