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PubMed1974

Calcium-containing electron-dense structures in the axons of the squid giant synapse.

Following the Oschman and Wall technique, electron-dense structures (EDS) were found on unstained, unosmicated membranes of squid giant synapse axons. These densities contain high concentrations of calcium and phosphorus as identified by energy dispersive X-ray analysis. Based on the signal strength, the quantity is significantly greater than that of other regions of the membrane or tissue spaces. The calcium EDS occur as plaques or globules along the axonic membrane, and small globules are found between sheath cell processes. EDS also occur at the synaptic site. These densities were correlated with the opacity change seen in giant axons. It is proposed that these structures represent sites where the calcium-binding protein found by other investigators has become nearly saturated with calcium.

Animals↗
PubMed1974

Association of calcium with membranes of squid giant axon: ultrastructure and microprobe analysis.

Giant axons from the squid, Loligo pealei, were fixed in glutaraldehyde and postfixed in osmium tetroxide. Calcium chloride (5 mM/liter) was added to all aqueous solutions used for tissue processing. Electron-opaque deposits were found along the axonal plasma membranes, within mitochondria, and along the basal plasma membranes of Schwann cells. X-ray microprobe analysis (EMMA-4) yielded signals for calcium and phosphorus when deposits were probed, whereas these elements were not detected in the axoplasm.

Animals↗
PubMed1998

Bacterial biofilm formation, encrustation, and antibiotic adsorption to ureteral stents indwelling in humans.

Encrustation and urinary tract infection are problematic complications of ureteral stent usage. The objective of our first study was to use surface science techniques to examine three ureteral stent types for encrustation, biofilm formation, and antibiotic adsorption after use in patients. Black Beauty (N = 16), LSe (N = 16), and SofFlex (N = 32) ureteral stents were recovered from patients who had received trimethoprim or ciprofloxacin while the stent was indwelling. These stents were examined with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy/energy-dispersive X-ray analysis (SEM/EDX) for the presence and composition of encrustation or biofilm. Conditioning films and encrustations were found on all stents. Encrustation elements (Ca, Mg, P) were identified on 11 of 16 Black Beauty (69%), 7 of 16 LSe (44%), and 12 of 32 SofFlex (38%) stents. The stent type, duration of insertion, and age or sex of the patient did not correlate significantly with the amount of encrustation. Bacterial biofilms were found on 1 of 7 Black Beauty stents (14%) and 7 of 32 SofFlex stents (22%). In a second study, an additional 28 patients with SofFlex stents were treated with ciprofloxacin (N = 16) or ofloxacin (N = 12). Their stents were subjected to high-performance liquid chromatography to determine if oral antibiotic therapy can lead to drug adsorption to the stent. Analysis showed that both ciprofloxacin and ofloxacin adsorbed to the stent surfaces. The mean concentrations of the two antibiotics within the conditioning film of the stents were 0.99 microg/mL and 0.34 microg/mL, respectively. These surface science techniques provide a comprehensive method of evaluating ureteral stents and other prosthetic devices in vivo.

Administration, Oral↗
PubMed1990

Characterization of airborne dust in a soft paper mill.

The characteristics of airborne dust in a soft paper production plant have been characterized by scanning and transmission electron microscopy. A combination of X-ray diffraction, electron diffraction and energy-dispersive X-ray flouresence spectroscopy (EDX) was used to determine the structure and composition of the different components. Size distribution determination and phase identification were carried out. Besides the cellulose fibres, fibres of kaolinite, wollastonite, talc and other silicates were also identified. Gravimetric analysis and fibre counting by optical phase contrast microscopy were used to determine total dust and fibre concentrations. Total dust exposure at the plant was generally below 3 mg m-3. The respirable fraction of the total dust concentrations varied from 15 to 70%. The inorganic dust was 36 +/- 15% of the total dust. The ratio of inorganic fibres to total fibre concentration at the plant varied between 10 and 15%.

Air Pollutants, Occupational↗
PubMed2000

Cytological changes in chlorhexidine-resistant isolates of Pseudomonas stutzeri.

Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) have been used to examine chlorhexidine diacetate (CHA)-sensitive and -resistant isolates of Pseudomonas stutzeri and to determine the effects of CHA on the cells. Significant differences were observed in the structure, size and elemental composition of CHA-sensitive and -resistant cells. Treatment with CHA produced considerably greater changes in CHA-sensitive cells, with widespread peeling of the outer membrane, a substantial loss of cytoplasmic electron-dense material and extensive lysis. Cells from the resistant isolates showed no blebbing of the outer membrane and no structural damage. X-ray mapping confirmed the difference in CHA uptake between CHA-sensitive and CHA-resistant cells. It is proposed that changes in the outer membrane form a major mechanism of resistance to CHA in P. stutzeri.

Chlorhexidine↗
PubMed2003

Reverse Monte Carlo analysis of extended energy-loss fine structure for disordered structures of tetrahedrally coordinated materials: its applicability.

Capabilities of the reverse Monte Carlo method for characterizing the short-range structural correlations of solids were examined in the analysis of extended energy-loss fine structure (EXELFS). Since this method gives a three-dimensional atomic configuration consistent with the experimental EXELFS spectra, one can extract the statistical distributions of bond lengths, coordination numbers and bond angles of atom species of interest, which have been hard to achieve by conventional EXELFS analysis. The method was applied for the determination of amorphous Si structures and the damaged structure of an electron-irradiated SiC crystal. Advantages and disadvantages of the present method over the precise diffraction intensity measurement are discussed.

Carbon↗
PubMed1989

Movement of endogenous calcium in the elongating zone of graviresponding roots of Zea mays.

Endogenous calcium (Ca) accumulates along the lower side of the elongating zone of horizontally oriented roots of Zea mays cv. Yellow Dent. This accumulation of Ca correlates positively with the onset of gravicurvature, and occurs in the cytoplasm, cell walls and mucilage of epidermal cells. Corresponding changes in endogenous Ca do not occur in cortical cells of the elongating zone of intact roots. These results indicate that the calcium asymmetries associated with root gravicurvature occur in the outermost layers of the root.

Calcium↗
PubMed1994

Crystallization and analyses of crystals of various chemotypes of R-form lipopolysaccharides from Salmonella spp.

Various chemotypes (Re, Rd2, Rd1P-, Rd1, RcP-, Rc, Rb3, Rb2, Rb1, and Ra) of R-form lipopolysaccharides (LPSs) of Salmonella spp. were crystallized by treatment with 70% ethanol containing 250 mM MgCl2, and crystals of the LPSs were observed electron microscopically and analyzed by electron diffraction and synchrotron X-ray diffraction. All the LPSs tested formed three-dimensional crystals showing very similar shapes; hexagonal plate, solid column, discoid, square or rectangular plate, lozenge plate and truncated hexangular or rectangular pyramid forms. Electron diffraction patterns from the hexagonal plate crystals of all these LPSs obtained by electron irradiation from the direction perpendicular to the basal plane showed that they consist of hexagonal lattices with the lattice constant of 4.62 A. The crystals of all the LPSs thus formed gave ring-like X-ray diffraction patterns because of their small sizes. The long-axis values were calculated from the X-ray diffraction patterns from crystals of all the LPSs in the low-angle region and they corresponded roughly to the length of the proposed primary chemical structures of the R cores of the LPSs. The volume occupied by a single molecule of all the LPSs were calculated from the molecular weights based on the proposed structures and the crystallographic data obtained by electron diffraction, X-ray diffraction, and density determination.

Crystallization↗
PubMed1976

The application of x-ray analysis in the transmission electron analytical microscope (T.E.A.M.) to the quantitative bulk analysis of biological microsamples.

This paper describes: (a)methods for the high and low temperature ashing of biological tissue samples about 10(-4)-10(-5) g in weight; (b)a method of spraying the solubilized ash on to specimen grids which produces droplets of a size convenient for their quantitative analysis in a transmission electron analytical microscope (T.E.A.M.), but without the need to know the actual volume of individual droplets; (c)the construction of standard curves for determining the absolute concentration of Na, Mg, P, S, K, and Ca simultaneously in a given sample. For most of the elements the error in analysis was about 5% or less. It was proposed that the technique is useful for detecting local element-compartments in complex tissues, and thus may be an important aid in the interpretation of the results of point analyses performed on sections taken from adjacent micro-volumes.

Calcium↗
PubMed1982

Transfer, observation and analysis of frozen hydrated specimens.

Hitherto, the observation of frozen hydrated specimens in transmission electron microscopes has been inhibited due to the technical difficulties experienced in transferring the specimen to the microscope and maintaining it at a low temperature during observation. This has resulted in loss of the primary advantage of freezing since the frozen water had to be removed from the specimen before it could be introduced into the electron microscope. The cryo-transfer system overcomes these objections and provides a means to transfer frozen hydrated specimens from any preparation equipment into the microscope without ice condensation on the specimen. The cryo-transfer system consists of a cryo-transfer unit, a cryo-specimen holder and a temperature control unit.

Electron Probe Microanalysis↗
PubMed1986

A simple method for correlative light, scanning electron microscopic and X-ray microanalytical examination of the same section.

Thin paraffin sections, mounted on scanning specimen holders previously coated with polyester film tape (Minnesota Mining and MFG Co., Scotch film tape No. 850 gold), were processed for light microscopy (LM) in the conventional way, then covered with celloxin shellac and examined in the LM by using the upper illuminating source. After removal of the shellac from the surface of the sample by immersion in acetone, the sections were air-dried, coated with a copper layer in a vacuum evaporator and examined in a scanning electron microscope (SEM). The method allows: (i) high-quality LM possibilities for establishment of the diagnosis in pathological cases; (ii) SEM examination of the same area as observed in LM; and (iii) EPMA measurements of insoluble precipitates embedded in the tissue. The usefulness of the proposed method is obvious in cases where the composition of a precipitate on LM scale is to be compared with the LM appearance of the surrounding tissue.

Animals↗
PubMed1992

Electron spectroscopic study (ESI, EELS) of Nanoplast-embedded mammalian lung.

The potential of Nanoplast melamine resin embedding for the study of mammalian lung parenchyma was examined by means of electron spectroscopic imaging (ESI) and electron energy-loss spectroscopy (EELS). Samples were either fixed with glutaraldehyde-paraformaldehyde or glutaraldehyde-tannic acid, or were directly transferred to the embedding medium without prior fixation. Organic dehydrants, as well as fixatives containing heavy metals and stains, were omitted. A very high level of ultrastructural detail of chromatin, ribosomes, mitochondria and plasma membranes was achieved by ESI from the Nanoplast-embedded samples. The most prominent gain in ultrastructural detail was achieved when moving from an energy loss just below the L2,3 edge of phosphorus at 132 eV to an energy loss just beyond this edge. This reflects the prominent P L2,3 edge observed by EELS of Nanoplast-embedded samples in comparison with conventionally processed samples. Thus, taking into account possible sectioning artefacts, excellent heterochromatin images which rely on the phosphorus distribution can be obtained from Nanoplast-embedded samples by computer-assisted analysis of electron spectroscopic images. In this respect glutaraldehyde-paraformaldehyde fixation is preferable to glutaraldehyde-tannic acid fixation because the presence of silicon, revealed by EELS, in tannic-acid-fixed samples may introduce artefacts in phosphorus distribution images obtained by the three-window method because of the close proximity of the L2,3 edges of silicon and phosphorus.

Animals↗
PubMed1984

The in vivo corrosion of Dispersalloy.

The in vivo corrosion of Dispersalloy amalgam restorations was characterized by scanning electron microscopy and energy dispersive X-ray analysis. It was observed that the corrosion of CuSn resulted in pitting on the restoration surface. Corrosion of Sn-rich grain boundaries led to intergranular separation of gamma 1 grains. The tin released through corrosion reacted with Ca, P, Cl and O forming various insoluble complexes on the external surface, at the tooth-amalgam interface, and within the interior of the restoration. The demineralization of the amalgam-adjacent margin has been attributed to corrosion.

Chemical Phenomena↗
PubMed1986

Solid solubility of tin in silver-mercury gamma 1 in dental amalgams.

The solid solubility of Sn in gamma 1 has been studied by examining a series of gamma 1 samples containing 0.25-2.0 wt% Sn by scanning electron microscopy and energy-dispersive X-ray analysis. It has been observed that the addition of Sn to gamma 1 leads to the formation of mainly an intergranular Sn-Hg compound. On the basis of this observation it has been concluded that the solubility of Sn in gamma 1 is virtually nil.

Chemical Phenomena↗
PubMed1990

Effects of axotomy on distribution and concentration of elements in rat sciatic nerve.

X-ray microprobe analysis was used to determine the effects of axotomy on distribution and concentration (millimoles of element per kilogram dry weight) of Na, P, Cl, K, and Ca in frozen, unfixed sections of rat sciatic nerve. Elemental concentrations were measured in axoplasm, mitochondria, and myelin at 8, 16, and 48 h after transection in small-, medium-, and large-diameter fibers. In addition, elemental composition was determined in extraaxonal space (EAS) and Schwann cell cytoplasm. During the initial 16 h following transection, axoplasm of small fibers exhibited a decrease in dry weight concentrations of K and Cl, whereas Na and P increased compared to control values. Similar changes were observed in mitochondria of small axons, except for an early, large increase in Ca content. In contrast, intraaxonal compartments of larger fibers showed increased dry weight levels of K and P, with no changes in Na or Ca concentrations. Both Schwann cell cytoplasm and EAS at 8 and 16 h after injury had significant increases in Na, K, and Cl dry weight concentrations, whereas no changes, other than an increase in Ca, were observed in myelin. Regardless of fiber size, 48 h after transection, axoplasm and mitochondria displayed marked increases in Na, Cl, and Ca concentrations associated with decreased K. Also at 48 h, both Schwann cell cytoplasm and EAS had increased dry weight concentrations of Na, Cl, and K. The results of this study indicate that, in response to nerve transection, elemental content and distribution are altered according to a specific temporal pattern. This sequence of change, which occurs first in small axons, precedes the onset of Wallerian degeneration in transected nerves.

Animals↗
PubMed2006

Osteoblast-like cells are sensitive to submicron-scale surface structure.

OBJECTIVES: Studies showing that osteoblasts exhibit a more differentiated phenotype on rough titanium (Ti) surfaces and osteoclast-resorbed bone surfaces used materials characterized by average peak to valley distance (Ra). Other surface features impacting the cells include distance between peaks, curvature of the valleys, and relative distribution of flat and smooth regions. We used novel Ti surfaces prepared by electrochemical micromachining as models to examine specific contributions of individual design features to osteoblast response. Results show that micron-scale topography modulates cell number, cell morphology and prostaglandin E2 (PGE2). In the presence of the appropriate microtopography, submicron-scale rugosity modulates differentiation and transforming growth factor-beta1 (TGF-beta1) levels. In this study, we examined the role of different types of submicron-scale structures. MATERIAL AND METHODS: Thirty micrometer diameter craters on Ti disks were produced by photolithography resulting in an electropolished smooth surface, and arranged so that inside crater area vs. outside flat area was 6 (30/6). Submicron-scale structures were superposed by acid etching and porous anodization. Ra's were 700, 400, 60 nm on acid-etched, porous anodized and smooth 30/6 surfaces, respectively. RESULTS: MG63 osteoblast-like cells were sensitive to submicron-scale architecture. Cell morphology on anodized surfaces was similar to morphology on smooth surfaces, whereas on etched surfaces, cells had a more elongated differentiated shape. Cell number was greatest on smooth surfaces > anodized > etched. Osteocalcin and PGE2 were affected in a reverse manner. Active TGF-beta1 was greatest on etched 30/6 surfaces > anodized > smooth; latent TGF-beta1 was elevated on all rough surfaces. CONCLUSIONS: These results support our previous observations that submicron-scale structures modulate osteoblastic phenotype and show that the physical properties of the submicron-scale structures are important variables in determining osteoblast response to substrate topography.

Acid Etching, Dental↗