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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↗

PubMed2004

Pulmonary fibre burden in sheep living in the Biancavilla area (Sicily): preliminary results.

In a national survey on mortality from malignant pleural neoplasms in Italy, aimed at detecting geographic clusters of cases of the disease, the town of Biancavilla, located in a volcanic area of Eastern Sicily, showed high risk of pleural mesothelioma in the absence of occupational asbestos exposure. An environmental survey suggested the stone quarries located in 'Monte Calvario', south-east of the town of Biancavilla, as a possible source of asbestiform fibre exposure. A subsequent crystal-chemistry investigation of the 'Monte Calvario' amphiboles identified the mineral asbestiform fibres as 'fluoro-edenite', a new end-member of the edenite ==> fluoro-edenite series. A collaborative epidemiological and environmental study was initiated to investigate the characteristics of the outbreak of malignant mesothelioma and test the hypothesis of a causal association with exposure to naturally occurring fibres. To investigate if a sheep population could be used to monitor the environmental diffusion of the fibres, we examined lung specimens from 27 culled sheep, at least 3 years old and living near Monte Calvario to check for the presence of fluoro-edenite fibres, using scanning electron microscopy (SEM) analysis and X-ray microanalysis. Fourteen mineral species have been isolated in the mineral particulate matter taken from pulmonary parenchyma, and fluoro-edenite was detected in eight sheep. These preliminary data suggest a possible bio-indicative role of sheep as sentinel animals in the evaluation of environmental fibre diffusion, which merits further investigation.

Animals↗

PubMed1981

Ultrastructural analysis and quantitative distribution of Macro-and microelements in young teeth hard tissues by the use of an X-ray microanalyser.

Determination of quantity, distribution and topography of calcium, phosphorus, magnesium and copper in transverse and longitudinal sections of deciduous and early erupted permanent human teeth were made by the use of an x-ray microanalyser and simultaneous analysis of the microstructure of the examined surface by the use of an electron scanning microscope. The examinations demonstrated the higher content of calcium and phosphorus, greater density and more homogenous distribution of these elements in the deciduous teeth. In the permanent teeth characteristic conglomerations of mineral granules were visible in the area corresponding to the dentine tubuli.

Calcium↗

PubMed2000

Modulation imaging in reflection-mode near-field scanning optical microscopy

A simple implementation of modulation of the near-field optical signal of near-field probes based on the shear-force feedback system is demonstrated in a reflection-mode near-field optical microscope. The modulation exhibits a derivative type of dependence on the near-field signal and no sensitivity to topography. It is shown that the modulation image can be calculated directly from the derivative of the conventional near-field scattering image. This type of near-field modulation is an excellent way to reject far-field artifacts from the near-field signal.

Journal Article↗

PubMed2004

Hemocyte-mediated shell mineralization in the eastern oyster.

The growth of molluscan shell crystals is usually thought to be initiated from solution by extracellular organic matrix. We report a class of granulocytic hemocytes that may be directly involved in shell crystal production for oysters. On the basis of scanning electron microscopy (SEM) and x-ray microanalysis, these granulocytes contain calcium carbonate crystals, and they increase in abundance relative to other hemocytes following experimentally induced shell regeneration. Hemocytes are observed at the mineralization front using vital fluorescent staining and SEM. Some cells are observed releasing crystals that are subsequently remodeled, thereby at least augmenting matrix-mediated crystal-forming processes in this system.

Animals↗

PubMed1989

Contact probes for intravascular laser recanalization. Experimental evaluation.

Experimental laser ablation of atheromatous plaques was performed with a bare quartz glass fiber, a metal probe, and a sapphire probe. The tissue response after irradiation with increasing energies was evaluated by means of light and scanning electron microscopy. Laser emission through the bare fiber caused a narrow, deep crater with an irregular surface surrounded by a zone of thermal necrosis. After tissue ablation with the metal probe, a disproportion between the small tissue defect and the large zone of thermal necrosis was observed. The largest tissue defect was vaporized by the sapphire contact probe. A small zone of thermal necrosis surrounded the laser crater.

Arteries↗

PubMed1986

Is mucus involved in biocrystallization? Study of the intestinal mucus of the sea-water eel Anguilla anguilla L.

Freeze-dried intestinal mucus of sea-water-adapted eels was analysed by scanning electron microscopy (SEM) and X-ray microanalysis. Calcite crystals were observed in the mucus fibres; their concentration increased along the hindgut. Random SEM observations made in situ indicated that mucus fibres were involved in the genesis of these crystals. Calcium-rich mucus globules were found fused inside crystal matrices. Single typical rhombohedric crystals of various complexity appeared within the mucus framework. The steps of crystal biogenesis were reconstituted in in-vitro conditions.

Anguilla↗

PubMed1983

Analysis of surface contaminants on intraocular lenses.

Surface contaminants have been studied on a variety of intraocular lenses by three methods: scanning electron microscopy, energy dispersive x-ray analysis (EDXA), and electron spectroscopy for chemical analysis (ESCA). Many particulate contaminants were observed on both commercially available lenses packaged for implantation and experimental batches of lenses. The nature of these particles could be inferred using the EDXA technique. Thin films of sodium dodecyl sulfate (SDS) that were resistant to removal were found on many of the lenses by ESCA. Cleaning procedures were developed that did not involve SDS and that generated extremely clean lens surfaces.

Animals↗

PubMed1980

[Scanning electron microscopy and x-ray microanalysis of the small intestine of suckling rabbits exposed to cholera toxin].

Surface alterations and elemental distribution in small intestinal enterocytes of suckling rabbits were studied by scanning electron microscopy and x-ray microanalysis. The latter was performed on 10 mu thick freeze-dried cryosections. Cholera toxin was found to diminish the sodium and chloride content in the epithelial layer from the cryptae towards the tops of the villi, while in control animals, no difference in the elemental distribution was revealed. The changes in the enterocyte surface consisted in the disarrangement of the microvilli and appearance of bullous enlargements on their tops.

Animals↗

PubMed1986

Identification of urinary stone and sediment crystals by scanning electron microscopy and x-ray microanalysis.

A procedure based on scanning electron microscopic techniques is described for the identification of crystals in urinary sediments and stones. The crystals are identified by their morphology and elemental composition using scanning electron microscopy and x-ray microanalysis. The procedure has a number of advantages over conventional methods. It is easy to use. It is non-destructive so that both the exterior and interior of the same stone can be separately analyzed. It is the only technique in which information about spatial relationships between various crystals in a stone can be obtained easily. Scanning electron microscopic techniques can detect minor components, and analysis of a wide variety of materials ranging from amorphous substances to microcrystals to macroscopic stones is possible.

Animals↗

PubMed1991

Line analysis of interface layer on dentin by means of electron-probe microanalysis.

Three types of brominated methacrylates, SBPPM, BPylM, and BNEM, were synthesized. The distribution of Br, Ca, and Fe at the interface between dentin treated with the 10-3 solution and resin containing these monomers was analyzed using an electron-probe microanalyzer (EPMA) in order to predict the composition and thickness of the interface layer on dentin for the corresponding unbrominated methacrylates. There was no significant difference between the brominated and unbrominated methacrylates in either the bond strength to the treated dentin or in the thickness of the interface layer on dentin observed with a scanning electron microscope (SEM). The thickness determined with EPMA was equivalent to that observed with SEM. The concentration of each brominated methacrylate in the interface layer was higher than the original concentration in the resin monomers, and BNEM showed higher concentration than the others. The presence of Fe in the layer was confirmed by EPMA.

Animals↗

PubMed2000

[Mixed tophi. Calcium pyrophosphate dihydrate crystals in gout tophi].

Calcification of tophi is a well-known secondary phenomenon in gout. Because there are no data available on the nature of the calcium component, light and scanning electron microscopic as well as X-ray microanalysis studies were performed on calcified tophi. In unstained histological slides, urate crystals were detected as negative birefringent needles; after incubation of the slides in distilled water, the urate crystals had disappeared, only positive birefringent calcium pyrophosphate dihydrate (CPPD) crystals of different size remained. An identical result was obtained by scanning electron microscopy. By X-ray microanalysis, peaks for calcium and phosphorus were measured, indicating the presence of CPPD. The occurrence of CPPD crystals in urate tophi as well as in foreign body granulomata indicates that the occurrence of CPPD is not restricted to articular tissues. The biochemical mechanism leading to the appearance of these crystals remains unknown, but it may be assumed that an increase of connective tissue destruction may be responsible for this calcification process.

Adult↗

PubMed2003

Characterization of hydrophobized pullulan with various hydrophobicities.

In this study, we prepared self-assembling nanospheres of hydrophobized pullulan. Pullulan acetate (PA), as hydrophobized pullulan, was synthesized by the acetylation of pullulan. PA derivatives were synthesized by changing the degree of acetylation. PA was characterized by Fourier transform infrared (FT-IR), X-ray diffractometry (XRD), and differential scanning calorimetry (DSC). The particle size distribution of the PA was determined using photon correlation spectroscopy (PCS) and the number-average particle size was found to depend upon the degree of acetylation of PA. Morphology by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed the PA nanospheres were spherical in shape. The fluorescence probe technique was used to study the self-association behavior of hydrophobized pullulans in water using pyrene as a hydrophobic probe. The critical association concentration (CAC) values were determined from the fluorescence excitation spectra, CAC values were dependent upon the degree of acetylation. Drug release studies using clonazepam (CNZ) as a hydrophobic model drug showed that the increased drug contents and increased degree of acetylation resulted in a slower release rate of drug from the nanospheres.

Acetylation↗

PubMed2000

Microfracture mechanisms of composite resins containing prepolymerized particle fillers.

The effect of prepolymerized particle fillers on fracture toughness of four commercial composite resins was studied. The ground surface morphology was examined with a field emission scanning electron microscope. Fracture toughness was determined by using single edge notched specimens. Acoustic Emission (AE), which is the elastic wave due to the release of energy from the localized sources of material, was detected by sensors of a high-sensitivity and low-noise resonance type during the fracture toughness test. Acoustic Emission signals detected were analyzed for parameters such as amplitude and energy. Fracture surfaces were examined with a scanning electron microscope. The fracture toughness values, AE releasing patterns during fracture toughness test, and the fracture surface findings were analyzed to understand the fracture behavior of composite resins containing prepolymerized particle fillers. A microfracture model and fracture mechanisms to increase the fracture toughness of this type of composite resins are proposed.

Acoustics↗

PubMed2001

Characterisation of 0.22 caliber rimfire gunshot residues by time-of-flight secondary ion mass spectrometry (TOF-SIMS): a preliminary study.

The application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) for the characterisation of gunshot residue (GSR) from 0.22 caliber rimfire ammunition is reported. Results obtained by TOF-SIMS were compared with conventional scanning electron microscopy (SEM) studies. As could be expected, TOF-SIMS exhibited greater elemental sensitivity than SEM equipped with energy dispersive X-ray detection (SEM-EDX), and was also capable of detecting fragments characteristic of inorganic compounds. This preliminary study indicates that TOF-SIMS offers substantial potential for forensic GSR examinations as a complementary technique to SEM-EDX. In addition TOF-SIMS is applicable to the analysis of individual particles in the typical size range encountered in GSR casework.

Electron Probe Microanalysis↗

PubMed2006

Linear least-squares fit evaluation of series of analytical spectra from planar defects: extension and possible implementations in scanning transmission electron microscopy.

In a previous paper, a new technique was introduced to determine the chemistry of crystallographically well-defined planar defects (such as straight interfaces, grain boundaries, twins, inversion or antiphase domain boundaries) in the presence of homogeneous solute segregation or selective doping. The technique is based on a linear least-squares fit using series of analytical (electron energy-loss or energy-dispersive X-ray) spectra acquired in a transmission electron microscope that is operated in nano-probe mode with the planar defect centred edge-on. First, additional notes on the use of proper k-factors and determination of Gibbsian excess segregation are given in this note. Using simulated data sets, it is shown that the linear least-squares fit improves both the accuracy and the robustness to noise beyond that obtainable by independently repeated measurements. It is then shown how the method originally developed for a stationary nano-probe mode in transmission electron microscopy can be extended to a focused electron beam that scans a square region in scanning transmission electron microscopy. The necessary modifications to scan geometry and corresponding numerical evaluation are described, and three different practical implementations are proposed.

Journal Article↗

PubMed1995

Polarization of mitochondria in the unfertilized mouse oocyte.

Maturation of an immature oocyte into one capable of being fertilized involves tightly choreographed movements of chromosomes and organelles. The localization of mitochondria during maturation was studied in live mouse oocytes by confocal laser scanning microscopy (CLSM). Mitochondria were labeled with rhodamine 123 or Mitotracker (Molecular Probes, Eugene, OR) both of which are cell permeant and accumulate in mitochondria; acridine orange was used to mark chromatin. Prior to maturation, oocytes appeared to be radially symmetrical with no evident polarity; fully mature oocytes exhibited obvious polarity marked by the position of the metaphase II spindle in the cortex. CLSM revealed several interesting features of mitochondrial distribution: 1) A cortical clump of mitochondria was seen approximately 30-45 degrees to one side of the metaphase II spindle and marked the region of polar body I extrusion. 2) Large foci of mitochondria (7-14 microM) were frequently found around the central region of the mature oocyte, while the central region often exhibited markedly fewer mitochondria. 3) Small mitochondrial foci (3 microM) in the cortex and near the GV characterized several oocytes which failed to mature. 4) Non-spindle-associated mitochondria were not uniformly distributed in the mature oocyte but were concentrated in the hemisphere containing the metaphase II spindle. 5) The distal margins of this mitochondrial hemisphere were sharply demarcated at the cortex. These findings should help us understand organelle localization during mammalian oocyte maturation, and may give insights into possible causes of infertility and into early events of preimplantation development.

1-Methyl-3-isobutylxanthine↗

PubMed2006

Preparation of biosensors by immobilization of polyphenol oxidase in conducting copolymers and their use in determination of phenolic compounds in red wine.

Electrochemically produced graft copolymers of thiophene capped polytetrahydofuran (TPTHF1 and TPTHF2) and pyrrole were achieved by constant potential electrolysis using sodium dodecylsulfate (SDS) as the supporting electrolyte. Characterizations were based on Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Electrical conductivities were measured by the four-probe technique. Novel biosensors for phenolic compounds were constructed by immobilizing polyphenol oxidase (PPO) into conducting copolymers prepared by electropolymerization of pyrrole with thiophene capped polytetrahydrofuran. Kinetic parameters, maximum reaction rate (V(max)) and Michaelis-Menten constant (K(m)) and optimum conditions regarding temperature and pH were determined for the immobilized enzyme. Operational stability and shelf-life of the enzyme electrodes were investigated. Enzyme electrodes of polyphenol oxidase were used to determine the amount of phenolic compounds in two brands of Turkish red wines and found very useful owing to their high kinetic parameters and wide pH working range.

Biosensing Techniques↗