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At least 1,171 records · Page 65Linked to original sources
PubMed2007

A novel method for the study of the biophysical interface in soils using nano-scale secondary ion mass spectrometry.

The spatial location of microorganisms and their activity within the soil matrix have major impacts on biological processes such as nutrient cycling. However, characterizing the biophysical interface in soils is hampered by a lack of techniques at relevant scales. A novel method for studying the distribution of microorganisms that have incorporated isotopically labelled substrate ('active' microorganisms) in relation to the soil microbial habitat is provided by nano-scale secondary ion mass spectrometry (NanoSIMS). Pseudomonas fluorescens are ubiquitous in soil and were therefore used as a model for 'active' microorganisms in soil. Batch cultures (NCTC 10038) were grown in a minimal salt medium containing 15N-ammonium sulphate (15/14N ratio of 1.174), added to quartz-based white sand or soil (coarse textured sand), embedded in Araldite 502 resin and sectioned for NanoSIMS analysis. The 15N-enriched P. fluorescens could be identified within the soil structure, demonstrating that the NanoSIMS technique enables the study of spatial location of microbial activity in relation to the heterogeneous soil matrix. This technique is complementary to the existing techniques of digital imaging analysis of soil thin sections and scanning electron microscopy. Together with advanced computer-aided tomography of soils and mathematical modelling of soil heterogeneity, NanoSIMS may be a powerful tool for studying physical and biological interactions, thereby furthering our understanding of the biophysical interface in soils.

Electron Probe Microanalysis↗
PubMed1984

Occurrence of fibrous sodium aluminumtetrafluoride particles in potrooms of the primary aluminum industry.

Inorganic fibrous particles have been found in the work environment of the primary aluminum industry. Based on scanning electron microscopic analysis, the concentrations ranged from 9 to 720 fibers/cc. The fibers were generally thinner than 0.1 micron in diameter and shorter than 5 microns. By electron microscopy, energy dispersive X-ray microanalysis, and selected area electron diffraction the fibers were identified as sodium aluminumtetrafluoride.

Air Pollutants, Occupational↗
PubMed2005

Nanomechanical sensing of DNA sequences using piezoresistive cantilevers.

A microfabricated cantilever with an internal piezoresistive component has been sensitized with thiol tethered ss-DNA strands and utilized for an in situ, label-free, highly specific, and rapid DNA detection assay. The generation of a differential surface stress onto the functionalized cantilever surface upon target recognition has allowed nanomechanical identification of 12-nucleotide complementary DNA probes with single base mismatch discrimination (sensitivity of 0.2 microM). Interestingly, utilization of an overhang extension distal to the surface enhanced the sensitivity to the 0.01 microM level. The cantilever was functionalized by inkjet printing technology. Replacing the capture probe with locked nucleic acid (LNA) resulted in a faster target probe capture kinetics compared to DNA-DNA hybridization. The capabilities of the piezoresistive cantilever indicate future ergonomic convenience via miniaturization alternative to the conventional laser-based detection method for portable on-site applications.

Base Sequence↗
PubMed1992

Protein images obtained by STM, AFM and TEM.

Scanning tunnelling microscopy and atomic force microscopy, one scanning the tunnelling current and the other the repulsive atomic force between same and probe, can give high-quality surface topographies of proteins, which have been difficult to obtain by more conventional methods such as transmission electron microscopy.

Macromolecular Substances↗
PubMedDate not supplied

Coral graft restoration of osteochondral defects.

The quality of osteochondral repair produced by coral grafted into subchondral bone was examined. Osteochondral defects of 4 mm diameter and 4 mm deep in left femoral grooves of 24 rabbits were repaired using plugs of natural coral or left empty to heal naturally as ungrafted controls. The right knees were kept intact for normal controls. The morphology of the repair tissue, at three and six months post operation, was characterised using histology and by scanning electron microscopy. Resorption of coral and its replacement by new bone was demonstrated using Energy Dispersive X-ray Analysis (EDXA) of the scanning electron microscope. The resorbing coral was gradually replaced by bone at subchondral bone level. The surface tissue matured with time and at six months it was anatomically similar to the adjacent hyaline cartilage: it contained cells that were shaped and arranged in columns similar to the normal controls. The ungrafted controls had healed with fibrous tissue which was often markedly thicker than the adjacent hyaline cartilage and was separated from the surrounding by vertical fissures. Coral grafting of the osteochondral defect enhanced repair of surface tissue.

Animals↗
PubMed1994

The microtrephine. A new diagnostic tool for obtaining corneal biopsies.

We have developed a new tool for obtaining biopsies of the cornea in a manner which is less traumatic than former biopsy techniques. The new instrument consists of a drill with an aperture of 160 microns which functions as a trephine and is powered at 30,000 rpm. The instrument contains a 120 microns mandrel to remove the samples. In order to monitor electrolyte contents in alkali burnt corneas, 32 rabbit eyes underwent an alkali burn of one cornea (1 n NaOH for 30 sec) followed by a sequence of microtrephinations at different times. A total of 81 microtrephinations were performed. Fifty samples were obtained. One corneal perforation occurred. Forty-four puncture sites were examined by means of histology. Forty-eight biopsies were examined in a scanning electron microscope and identified as punctures of corneal tissue by way of an energy dispersive X-ray analysis. Human corneas had been punctured with this device.

Animals↗
PubMedDate not supplied

The effect of fast secondary electrons on x-ray microanalysis in the scanning electron microscope.

In this paper, the effect of fast secondary electrons (FSE), which result from inelastic scattering of incident electrons, on the characterization of materials in the scanning electron microscope are investigated with the aid of Monte Carlo simulations. The effect of FSE on x-ray microanalysis of light elements is investigated. A full description of the Monte Carlo simulations of FSE in solids is given.

Boron↗
PubMed2005

Observation of the morphology and calcium content of vestibular otoconia in rats after simulated weightlessness.

Reduction in bone formation may have been the main reason for the lower calcium content of the otoconia after simulated weightlessness in rats. The head-ward distribution of blood volume may explain the morphological changes observed in the middle and inner ears. To observe morphological changes in the vestibular organs and measure the calcium content of otoconia in rats after simulated weightlessness. We used a tail suspension model of simulated weightlessness and then investigated changes in the vestibular organs using scanning electron microscopy and X-ray microanalysis. In comparison to untreated rats, the vestibular otoconia of the rats subjected to simulated weightlessness were small, irregularly shaped or fissured, and were arranged loosely and out of order. In addition, the calcium content of the otoconia was markedly decreased.

Animals↗
PubMed1987

Role of scanning electron microscopy and x-ray microanalysis in the identification of urinary crystals.

Urinary crystals can be identified by using analytical electron microscopic techniques of scanning electron microscopy and energy dispersive x-ray microanalysis. Crystal habit can be recognised by scanning electron microscopy and their chemical nature by elemental analysis. With a conventional detector the lightest element that can routinely be detected is sodium, but with a windowless or thin window detector even carbon can be detected. Thus almost all the commonly occurring urinary crystals including uric acid can be analysed by energy dispersive x-ray microanalysis.

Calcium↗
PubMed1979

Scanning x-ray microanalysis of root canal sealers.

Seven commercially available root canal sealer powders were analyzed by scanning x-ray microanalysis to identify constituent elements in each. Analysis showed that strongly cytotoxic sealers in vitro contained lead or magnesium, while those materials which exhibited mild or moderate cytotoxicity in vitro contained bismuth, zinc, calcium, or silicone.

Dental Cements↗
PubMed1987

Etching patterns of Co-Cr alloys for bonded cast restorations.

Resin-bonded bridges may replace missing teeth and act as splints in periodontal treatment. The objective of this study was to investigate the etch pattern after electrolytic etching of selected Co-Cr alloys in hydrochloric acid and to assess the changes in alloy composition after different etching times. The alloys investigated were Vitallium, Wironit, Wironium, Nobilium Hard, and Niranium NN. Alloy specimens were electrolytically etched in a hydrochloric acid solution for 1, 2, 5, and 10 min. The etched specimens were examined in a light microscope and a scanning electron microscope (SEM). Different etching patterns were revealed in the various alloys. Microprobe analyses after the etching of Vitallium showed generally that Co was released and that Cr content increased at the surface.

Acid Etching, Dental↗
PubMed2005

Three distinct read-out modes for enzyme activity can operate in a semi-wet supramolecular hydrogel.

Assays of hydrolytic enzyme activity, such as of glycosidases and phosphatase, as well as several proteases, using a semi-wet supramolecular hydrogel array composed of a glycosylated amino acetate are described. It has been demonstrated that the microcavity formed by gel fibrils is suitable to immobilize native enzymes without denaturation under semi-wet conditions, and thus the nanofiber has been rationally used as a sensing domain to monitor enzymatic reactions. By using a fluorogenic substrate, reducing the size of the hydrogel can significantly improve the problem of suppressed diffusion within the gel matrix thus making the hydrogel a promising semi-wet matrix for evaluating enzyme activity. Confocal laser scanning microscopy observations have shown that an environmentally sensitive fluorescent probe accumulates in the hydrophobic domain of the gel fiber and emits fluorescence more strongly upon hydrolytic cleavage of the substrate peptides. Not only a simple environmentally sensitive probe but also a FRET (fluorescence resonance energy transfer)-type read-out mode can be devised to analyze the enzymatic hydrolysis-triggered redistribution of the probe between the nanospace and the nanofiber to accomplish a more clearly distinguished enzyme assay. Thus, it is clear that three distinct read-out modes, that is, 1) fluorogenic substrates, 2) substrates bearing an environmentally sensitive probe, or 3) a substrate exhibiting FRET, can operate under the semi-wet hydrogel conditions used in these investigations. In addition, owing to the unique properties of the present supramolecular hydrogel in semi-wet conditions, that is, its phase-segregation properties and dynamics, the supramolecular substrate/enzyme array has successfully been used for high-throughput screening of single and multiple enzymes based on their activity, lysate analysis, and quantitative evaluation of inhibitor potency and selectivity.

Enzyme Inhibitors↗
PubMed2002

Microscale evaluation of the effects of grazing by invertebrates with contrasting feeding modes on river biofilm architecture and composition.

River biofilms are a valuable food resource for many invertebrates. In the present study biofilms were cultivated in a rotating annular bioreactor with river water as sole source of inoculum. The resulting biofilms were then presented to starved snails, ostracods, and mayflies as sole food source. The biofilms were then removed and microscopically examined to determine areas that had been grazed. The grazed and ungrazed areas were marked and analyzed for the effects of grazing using confocal laser scanning microscopy and image analyses. Samples were treated with fluorescent probes for nucleic acids to quantify bacterial biomass and fluor-conjugated lectins to quantify exopolymer, and far red autofluorescence was imaged to quantify algal or photosynthetic biomass. Grazing by snails significantly reduced algal biomass (1.1 +/- 0.6 micro m 3 micro m 2 to 0.02 +/- 0.04 micro m 3 micro m 2), exopolymer (5.3 +/- 3.4 micro m 3 micro m 2 to 0.18 +/- 0.18 micro m 3 micro m 2), and biofilm thickness (154 micro m +/- 50 to 11 micro m +/- 5.2; ANOVA, p < or= 0.05). Although bacterial biomass was influenced by grazing snails the impact was not statistically significant (p <or= 0.05). Ostracods had a significant (p <or= 0.05) impact on the algal biomass and exopolymer but not on bacteria. Mayfly grazing resulted in reduction of biofilm thickness to approximately 40 mm and reductions in all biofilm components with little evidence of selectivity. Thus grazing consistently resulted in a significant reduction in autotrophic biomass and exopolymer with a resultant increased importance of bacterial biomass within the grazed regions. Examination of grazed biofilms after a recovery period in the absence of grazing indicated that grazed regions remained predominantly bacterial after 28 days. A comparison of grazing in diclofop methyl and atrazine contaminated (1 ppb and 10 ppb) versus control biofilms indicated no significant influence of the contaminants on grazing patterns.

Animals↗
PubMed2005

Atypical cutaneous leishmaniasis in Central America: possible interaction between infectious and environmental elements.

Biopsies of 71 cases of atypical cutaneous leishmaniasis from Costa Rican patients were evaluated by histopathological procedures and attempts were made to culture Leishmania from nine biopsies. Leishmanin skin tests were carried out in 31 patients and 112 healthy individuals. Additional biopsies from 19 patients from Nicaragua were evaluated by routine histopathology. Ten biopsies were studied by confocal and nine by scanning electron microscopy. Inorganic material was analysed using an electron probe for microanalysis. Leishmania parasites were isolated from only two biopsies, but 90.3% of the patients from Costa Rica were leishmanin-positive, as were 27.7% of healthy individuals. Routine histopathological studies revealed naked granulomas formed by differentiated macrophages. Abundant inorganic material was observed in sections examined by confocal microscopy. Electron probe analysis revealed that silica and aluminium were the predominant elements in large particles. We postulate that the presence of this inorganic material, possibly of volcanic origin, in the skin may modulate the immunological response to Leishmania and may inhibit visceralization in the cases caused by Leishmania chagasi.

Adolescent↗
PubMed1999

Crystal growth of carbonate apatite using a CaCO3 flux.

Single crystals of carbonate apatite were grown using a CaCO3 flux under an Ar gas pressure of 55 MPa. The crystals obtained were observed by scanning electron microscopy, optical microscopy and X-ray diffraction. Electron probe microanalyses and thermal analyses were performed. CO3 ions in planar triangle form replaced both OH sites and PO4 tetrahedral sites in the apatite structure: in particular, the OH sites were perfectly substituted by CO3 ions using this method.

Journal Article↗