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At least 1,135 records · Page 63Linked to original sources
PubMed1982

Mass determination of thin biological specimens for use in quantitative electron probe X-ray microanalysis.

In the quantitative electron probe X-ray microanalysis of thin specimens the total mass thickness of a specimen is often required to express the elemental content as fractions of the total mass. In the present paper three methods for the measurement of mass thickness of thin specimens are reviewed and compared as to their applicability for use in quantitative X-ray microanalysis. The methods are based on the use of the continuum X-ray intensity, the backscattered electron intensity, and the transmitted electron intensity, respectively. From experimental results, it is concluded that the mass measurement method, based on the transmitted electron intensity, gives more accurate mass values than does the continuum X-ray method. The use of an independent mass measurement method is advantageous when low temperature oxygen plasma ashing is applied to lower X-ray analysis detection limits. In this way, elements present in ashed specimens can be expressed as fractions of the original specimen mass.

Animals↗
PubMed1996

Effect of surface topography of titanium on surface chemistry and cellular response.

Surface topography plays a critical role in the interaction of dental implants with adjacent tissues. It has been hypothesized that an increase in surface roughness will result in an increase in calcium and phosphorus deposition after immersion in a simulated physiological solution and will increase protein production and calcium uptake by osteoblast-like cells. With the use of a profilometer, titanium samples ground with 600 grit silicon carbide paper were observed to have an average roughness (Ra) value of 0.28 +/- 0.03 micron, whereas titanium samples polished with 0.3 micron Al2O3 exhibited a Ra value of 0.11 +/- 0.01 micron. X-ray photoelectron spectroscopy analyses indicated the presence of calcium, phosphorus, sodium, and chlorine on both surface conditions after immersion in a protein-free physiologic solution. No significant difference in calcium and phosphorus concentrations were observed between the 600 grit or Al2O3 polished titanium samples after immersion in solution. The Ca/P ratio for both 600 grit and Al2O3 polished titanium was in the range of 0.8 to 1.1 after 12 days in solution. The percent protein retained by the rat bone marrow cell layer on both the Al2O3 polished and 600 grit titanium surfaces increased dramatically during the initial 3 days of the study. The 45Ca assays revealed no significant difference in cellular calcification on Al2O3 polished and 600 grit titanium surfaces. For both the Al2O3 polished and 600 grit surfaces, a sharp increase in 45Ca incorporation was observed after 9 days incubation.

Aluminum Oxide↗
PubMed1989

Probing of the canine mammary artery damages endothelium and impairs vasodilation resulting from prostacyclin and endothelium-derived relaxing factor.

It is routine practice for many cardiac surgeons to probe internal mammary arteries to dilate them before their use. The effects of such probing on endothelium integrity, prostacyclin production, and vasodilation resulting from endothelium-derived relaxing factor and from prostacyclin were investigated in vessels isolated from mongrel dogs. Dose-dependent relaxation responses of isolated segments of probed and unprobed mammary arteries to the endothelium-dependent vasodilators methacholine, calcium ionophore (A23187), and melittin were determined in both the presence and absence of indomethacin. Prostacyclin production by probed versus unprobed vascular segments was determined under basal and A23187-stimulated conditions by radioimmunoassay for 6-keto-prostaglandin F1 alpha, and endothelial integrity was determined by scanning electron microscopy. Scanning electron micrographs of segments revealed marked endothelial cell disruption in probed versus unprobed vessels. The dose-dependent relaxation responses to all drugs studied were significantly impaired (p less than 0.05) in probed versus unprobed vessels in both the presence and absence of indomethacin. In addition, prostacyclin release as measured by production of 6-keto-prostaglandin F1 alpha was significantly (p less than 0.05) impaired in probed versus unprobed vessels under both basal and A23187-stimulated conditions. These results imply that routine probing of the internal mammary artery may damage endothelium, impair prostacyclin production, and impair endothelium-dependent vasodilation resulting from both prostacyclin and endothelium-derived relaxing factor.

Animals↗
PubMed1988

Electron probe X-ray microanalysis of the composition of hyaline articular and non-articular cartilage in young and aged rats.

Blocks of articular cartilage were taken from tibiae of young adult (8 week) and aged adult (50-60 week) rats; xiphisternal cartilage was obtained from young adult rats. Specimens were quench-frozen in nitrogen slush, freeze-fractured and examined by low-temperature scanning electron microscopy. The results of X-ray microanalysis of frozen-hydrated bulk cartilage are semi-quantitative. The composition of chondrocyte nuclei and cytoplasm are only marginally different. Xiphisternal chondrocytes contain lipid inclusions which show an absence of element peaks and are designated as being neutral lipid. Intra- and extracellular Na, P, S, Cl, K and Ca count rates are significantly different. Cartilage from older rats contains more S and Ca, and less K and Cl in the intercellular matrix than that from young rats. Intracellular K levels are lower in aged than in young rats. The intercellular matrix of xiphisternal cartilage contains larger amounts of S, Na and K, and a smaller amount of Cl compared to that of tibial articular cartilage.

Aging↗
PubMed1994

Thick-section fluorescence in situ hybridization on formalin-fixed, paraffin-embedded archival tissue provides a histogenetic profile.

Fluorescence in situ hybridization has become a major tool for analysis of gene and chromosome copy number in normal and malignant tissue. The technique has been applied widely to fresh tissue and dispersed formalin-fixed, paraffin-embedded archival tissue, but its use on sections of archival tissue has largely been limited to sections < 6 mu thick. This does not provide intact, uncut nuclei for accurate analysis of gene or chromosome copy number. We report here a method of hybridization to sections > 20 microns thick that overcomes these difficulties. Key developments were the use of DNA probes directly labeled with fluorochromes and optical sectioning using laser-scanning confocal microscopy.

Chromosomes, Human, Pair 1↗
PubMed1975

Intranuclear silicon detection in a subcutaneous connective tissue cell by energy-dispersive x-ray miscroanalysis using fresh air-dried spread.

Silicon was detected by energy-dispersive x-ray microanalysis in the nucleus of a subcutaneous connective tissue cell of mice fed normally. To eliminate contamination, pieces of connective tissue were spread on copper grids and examined without any treatment by an energy-dispersive spectrometer with a scanning transmission apparatus attached to an electron microscope. Scanning transmission electron microscopy of the spread has demonstrated a well-preserved ultrastructure. Fibrous structures, nuclei and nucleoli of cells and mitochondrial granules were recognized. Electron probe analysis showed peaks for silicon at three spots on the nucleus of a cell in addition to those for phosphorus, sulfur, chlorine, potassium and calcium, whereas no peak of silicon could be detected at the spots on nuclei of other cells, mitochondrial granules and electron-lucent area on the same grid as the above. Silicon appears to play a significant role in the nucleus. Applicability of the technique to know the distribution of easily contaminating elements and diffusible substances is shown.

Air↗
PubMedDate not supplied

Detection of calcifications in breast biopsies by scanning electron microscopy.

The identification of microcalcifications in breast biopsy specimens is a common and important task for the surgical pathologist that may sometimes be problematic. Although visualized by preoperative mammographic and operative specimen radiography, some cases may fail to reveal calcifications by histopathologic examination or occasion laborious and time-consuming study to confirm sparse calcifications. The present study demonstrates how conventional bright-field and polariscopic light microscopy did require considerable effort to confirm rare calcification. On the other hand, scanning electron microscopy was employed directly on a routine slide and provided definitive visual and physical proof, e.g., by means of energy dispersive x-ray microanalysis of a rare calcification on a slide previously judged to be negative for calcium and in a short period of time. Recent instrument advances in high voltage beam stabilization and in the ability to vary the pressure of the scanning electron microscope in the vicinity of the specimen now allow complete insertion of a diagnostic glass slide with only trivial preparation. The report, although brief, raises important questions regarding the extent and prevalence of breast calcifications.

Adult↗
PubMedDate not supplied

Modular, self-assembling peptide linkers for stable and regenerable carbon nanotube biosensor interfaces.

As part of an effort to develop nanoelectronic sensors for biological targets, we tested the potential to incorporate coiled coils as metallized, self-assembling, site-specific molecular linkers on carbon nanotubes (CNTs). Based on a previously conceived modular anchor-probe approach, a system was designed in which hydrophobic residues (valines and leucines) form the interface between the two helical peptide components. Charged residues (glutamates and arginines) on the borders of the hydrophobic interface increase peptide solubility, and provide stability and specificity for anchor-probe assembly. Two histidine residues oriented on the exposed hydrophilic exterior of each peptide were included as chelating sites for metal ions such as cobalt. Cysteines were incorporated at the peptide termini for oriented, thiol-mediated coupling to surface plasmon resonance (SPR) biosensor surfaces, gold nanoparticles or CNT substrates. The two peptides were produced by solid phase peptide synthesis using Fmoc chemistry: an acidic 42-residue peptide E42C, and its counterpart in the heterodimer, a basic 39-residue peptide R39C. The ability of E42C and R39C to bind cobalt was demonstrated by immobilized metal affinity chromatography and isothermal titration calorimetry. SPR biosensor kinetic analysis of dimer assembly revealed apparent sub-nanomolar affinities in buffers with and without 1 mM CoCl2 using two different reference surfaces. For device-oriented CNT immobilization, R39C was covalently anchored to CNT tips via a C-terminal cysteine residue. Scanning electron microscopy was used to visualize the assembly of probe peptide (E42C) N-terminally labeled with 15 nm gold nanoparticles, when added to the R39C-CNT surface. The results obtained open the way to develop CNT tip-directed recognition surfaces, using recombinant and chemically synthesized chimeras containing binding epitopes fused to the E42C sequence domain.

Biosensing Techniques↗
PubMed2002

Specific fluorescent tracers. Imaging and applications for photodynamic therapy.

Our main objective is to enlarge the fluorescence use in biosciences, with especially the photodynamic therapy (PDT) used for cancer treatment as one of the target applications. Meta-tetra(hydroxyphenyl)chlorin (m-THPC) is a second-generation photosensitiser, applied in photodynamic therapy. The localisation of this sensitiser as well as its induced cell death mechanisms in human breast cancer cells (MCF-7 and its resistant subline MCF-7DXR, DXR: doxorubicin) were evaluated using fluorescence microscopy. In addition, we will present two additional routes, whose aims are to create new features to respond to the PDT questioning: firstly, the synthesis of fluorescent tracers, with a particular attention to the presence of hydrophilic groups (glucosamine ring) on the basic fluorophore structure to orientate the localisation of the probe and, secondly, the use of scanning near-field optical microscopy to reach a better resolution for the fluorescence microscopy analysis.

Biological Transport↗
PubMed2004

Imaging and analysis of nanowires.

We used vapor-liquid-solid (VLS) methods to synthesize discrete single-element semiconductor nanowires and multicomposition nanowire heterostructures, and then characterized their structure and composition using high-resolution electron microscopy (HRTEM) and analytical electron microscopy techniques. Imaging nanowires requires the modification of the established HRTEM imaging procedures for bulk material to take into consideration the effects of finite nanowire width and thickness. We show that high-resolution atomic structure images of nanowires less than 6 nm in thickness have lattice "streaking" due to the finite crystal lattice in two dimensions of the nanowire structure. Diffraction pattern analysis of nanowires must also consider the effects of a finite structure producing a large reciprocal space function, and we demonstrate that the classically forbidden 1/3 [422] reflections are present in the [111] zone axis orientation of silicon nanowires due to the finite thickness and lattice plane edge effects that allow incomplete diffracted beam cancellation. If the operating conditions are not carefully considered, we found that HRTEM image delocalization becomes apparent when employing a field emission transmission electron microscope (TEM) to image nanowires and such effects have been shown to produce images of the silicon lattice structure outside of the nanowire itself. We show that pseudo low-dose imaging methods are effective in reducing nanowire structure degradation caused by electron beam irradiation. We also show that scanning TEM (STEM) with energy dispersive X-ray microanalysis (EDS) is critical in the examination of multicomponent nanowire heterostructures.

Computer Simulation↗