Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Microscopy”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed2003

Evaluation of lateral resolution of scanning surface microscopy by total internal reflection with thermal lens effect.

We have developed a novel method for in situ and non-destructive surface analyses, or a total internal reflection with thermal lens spectroscopy (TIR-TLS), which has sufficient sensitivity to monitor phenomena in thin films, such as lipid bilayers. In this study, we applied TIR-TLS to microscopy for surface analyses, and we experimentally obtained its lateral resolution using the edge of a chromium film made by a photolithography technique. The obtained resolution was 20 microm, which was 60% of the diameter of an excitation beam at the interface. The estimated resolution with a simple model agreed with the experimental one, and from this model, TIR-TLS microscopy has the same resolution as that of ordinary optical microscopy. The microscopy by TIR-TLS was applied to a sample whose contrast was too weak to be visually seen, and an image of the sample was obtained without any loss of resolution.

Journal Article↗
PubMedDate not supplied

Single molecule mapping of the optical field distribution of probes for near-field microscopy.

The most difficult task in near-field scanning optical microscopy (NSOM) is to make a high quality subwavelength aperture probe. Recently, we have developed high definition NSOM probes by focused ion beam (FIB) milling. These probes have a higher brightness, better polarization characteristics, better aperture definition and a flatter end face than conventional NSOM probes. We have determined the quality of these probes in four independent ways: by FIB imaging and by shear-force microscopy (both providing geometrical information), by far-field optical measurements (yielding throughput and polarization characteristics), and ultimately by single molecule imaging in the near-field. In this paper, we report on a new method using shear-force microscopy to study the size of the aperture and the end face of the probe (with a roughness smaller than 1.5 nm). More importantly, we demonstrate the use of single molecules to measure the full three-dimensional optical near-field distribution of the probe with molecular spatial resolution. The single molecule images exhibit various intensity patterns, varying from circular and elliptical to double arc and ring structures, which depend on the orientation of the molecules with respect to the probe. The optical resolution in the measurements is not determined by the size of the aperture, but by the high optical field gradients at the rims of the aperture. With a 70 nm aperture probe, we obtain fluorescence field patterns with 45 nm FWHM. Clearly, this unprecedented near-field optical resolution constitutes an order of magnitude improvement over far-field methods like confocal microscopy.

Journal Article↗
PubMed2001

Transmission electron microscopy studies of squeeze cast Al-AlN composites.

Aluminium-matrix composites containing approximately 45 vol.% AlN particles were fabricated by melt infiltration of aluminium into an AlN preform under a pressure up to 130 MPa. Three types of aluminium alloy (2024, 6060 and 5754) were used. The as-prepared composites were studied by light microscopy, scanning and transmission electron microscopies, and energy-dispersive X-ray spectroscopy. As a result of the melt infiltration process, the composites are very dense and the microstructure shows a homogeneous distribution of the reinforcement. The interfaces are clean with very little porosity. Composites with 2024 and 6060 matrices were carefully studied by transmission electron microscopy (TEM) and high resolution electron microscopy (HREM) after heat treatments. Dislocation density in the matrix of the reinforced material increases due to the difference in thermal expansion coefficients of aluminium alloys and AlN. This can induce an accelerated ageing response of the coherent and semicoherent precipitations of age-hardened matrices. This behaviour has been studied in the 2024 and 6060 composites by using microhardness measurements and TEM. Reactions between the AlN reinforcement and aluminium matrices (6060 and 5754) were observed and analysed by TEM. Matrices containing some of magnesium display a MgAl2O4 spinel formation at the AlN/matrix interface. The spinel formation is probably due to the reaction between magnesium of the matrix and the thin Al2O3 layer on the AlN surfaces. This reaction can affect the mechanical behaviour of the composite infiltrated with the 5754 matrix. This has been confirmed by overageing some samples at high temperatures (300 degrees C and 550 degrees C) for 10 days in order to emphasize the interfacial reactions.

Journal Article↗
PubMed2002

Electron and light microscopy studies on the domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I ferroic boracites.

The domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I boracite single crystals were studied by means of polarized light in conjunction with electron microscopy. Single crystals of the three compositions were grown by chemical transport reactions in closed quartz ampoules, at a temperature of 900 degrees C and were examined by polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For both PLM and SEM, the same as-grown samples were used without having to resort to metallization of the crystal faces. For TEM the single crystals were crushed and mounted on holey carbon films. Comparative electron microscope images were useful for revealing the domain structure of these ferroelectric/ferroelastic materials previously observed between the crossed polars of an optical microscope. X-ray diffraction analysis of the pulverized crystals was performed for this triad of halogen boracites containing zinc as a common metal.

Journal Article↗
PubMed2003

Current-sensing scanning near-field optical microscopy using a metal probe for nanometre-scale observation of electrochromic films.

A novel technique for scanning near-field optical microscopy capable of point-contact current-sensing was developed in order to investigate the nanometre-scale optical and electrical properties of electrochromic materials. An apertureless bent-metal probe was fabricated in order to detect optical and current signals at a local point on the electrochromic films. The near-field optical properties could be observed using the local field enhancement effect generated at the edge of the metal probe under p-polarized laser illumination. With regard to electrical properties, current signal could be detected with the metal probe connected to a high-sensitive current amplifier. Using the current-sensing scanning near-field optical microscopy, the surface topography, optical and current images of coloured WO3 thin films were observed simultaneously. Furthermore, nanometre-scale electrochromic modification of local bleaching could be performed using the current-sensing scanning near-field optical microscopy. The current-sensing scanning near-field optical microscopy has potential use in various fields of nanometre-scale optoelectronics.

Journal Article↗
PubMed1982

The detection of effaced podocytes by high resolution light microscopy.

Fifteen cases of renal minimal change disease and five normal glomeruli were studied by high resolution light microscopy (HRLM) and transmission electron microscopy (TEM). Effacement of podocytes usually is accompanied by aggregation of microfilaments in the cytoplasm of the epithelial cells parallel to the glomerular basement membrane (GBM). The aggregated microfilaments were detected as a dense blue line by high resolution light microscopy. The presence of this line appears to be a reliable sign for the detection of diffusely effaced podocytes by light microscopy. However, when effacement of podocytes was not accompanied by the condensation of microfilaments, the detection of this change by HRLM was more difficult.

Cytoskeleton↗
PubMed2007

The use of Raman microscopy to determine and localize vitamin E in biological samples.

Alpha-tocopherol (aT), the predominant form of vitamin E in mammals, is thought to prevent oxidation of polyunsaturated fatty acids. In the lung, aT is perceived to be accumulated in alveolar type II cells and secreted together with surfactant into the epithelial lining fluid. Conventionally, determination of aT and related compounds requires extraction with organic solvents. This study describes a new method to determine and image the distribution of aT and related compounds within cells and tissue sections using the light-scattering technique of Raman microscopy to enable high spatial as well as spectral resolution. This study compared the nondestructive analysis by Raman microscopy of vitamin E, in particular aT, in biological samples with data obtained using conventional HPLC analysis. Raman spectra were acquired at spatial resolutions of 2-0.8 microm. Multivariate analysis techniques were used for analyses and construction of corresponding maps showing the distribution of aT, alpha-tocopherol quinone (aTQ), and other constituents (hemes, proteins, DNA, and surfactant lipids). A combination of images enabled identification of colocalized constituents (heme/aTQ and aT/surfactant lipids). Our data demonstrate the ability of Raman microscopy to discriminate between different tocopherols and oxidation products in biological specimens without sample destruction. By enabling the visualization of lipid-protein interactions, Raman microscopy offers a novel method of investigating biological characterization of lipid-soluble compounds, including those that may be embedded in biological membranes such as aT.

Antioxidants↗
PubMed2000

Pathology of late endothelial failure: late endothelial failure of penetrating keratoplasty: study with light and electron microscopy.

PURPOSE: Late endothelial failure of penetrating keratoplasty can be defined as gradual decompensation (increasing thickness with loss of clarity) of a previously clear graft without apparent cause. This study examined the possibility that a chronic subclinical rejection process may be occurring in grafts that fail from late endothelial failure. METHOD: Six patients fulfilling the diagnostic criteria for late endothelial failure who underwent repeated keratoplasty were studied. The clinical course and results of specular microscopy were reviewed. The failed corneal graft for each patient was examined by light and electron microscopy. RESULTS: Sequential specular microscopy demonstrated low initial postoperative endothelial cell density with continued decrease in density and increase in corneal thickness over the first 5 postoperative years. Electron microscopy revealed irregular-shaped cells of varying size with many abnormal features, lying on abnormal Descemet's membrane. Degenerating endothelial cells were commonly seen. There was no sign of acute or chronic inflammation. CONCLUSIONS: The pathologic findings are suggestive of an unstable and highly stressed endothelial cell population in late endothelial failure but are nonspecific. There was no evidence of acute or chronic rejection at the time of graft failure.

Adult↗
PubMed2002

Skeletal dosimetry via NMR microscopy: investigations of sample reproducibility and signal source.

Nuclear magnetic resonance microscopy has been used for several years as a means of quantifying the 3D microarchitecture of the cancellous regions of the skeleton. These studies were originally undertaken for the purpose of developing non-invasive techniques for the early detection of osteoporosis and other bone structural changes. Recently, nuclear magnetic resonance microscopy has also been used to acquire this same 3D data for the purpose of both (1) generating chord length data across bone trabeculae and marrow cavities and (2) generating 3D images for direct coupling to Monte Carlo radiation transport codes. In both cases, one is interested in the reproducibility of the dosimetric data obtained from nuclear magnetic resonance microscopy. In the first of two studies, a trabecular bone sample from the femoral head of a 51-y-old male cadaver was subjected to repeated image acquisition, image processing, image coupling, and radiation transport simulations. The resulting absorbed fractions at high electron energies (4 MeV) were shown to vary less than 4% among four different imaging sessions of the same sample. In a separate study, two femoral head samples were imaged under differing conditions of the NMR signal source. In the first case, the samples were imaged with intact marrow. These samples were then subjected to marrow digestion and immersed in Gd-doped water, which then filled the marrow cavities. Energy-dependent absorbed fraction profiles for both the marrow-intact and marrow-free samples showed essentially equivalent results. These studies thus provide encouragement that skeletal dosimetry models of improved patient specificity can be achieved via NMR microscopy in vivo.

Bone and Bones↗
PubMed2006

Urine microscopy as screen for urinary tract infections in a pediatric emergency unit in Chile.

OBJECTIVE: To evaluate the accuracy of urine microscopy as a predictor of urinary tract infections (UTIs), taking the urine culture as a criterion standard in a pediatric emergency unit. METHODS: Retrospective study in which all medical charts were analyzed for children younger than 15 years who underwent urine culture and sediment tests. Urine microscopy test was considered positive for leukocyturia when there were more than 10 leukocytes per microliter, and bacteriuria test was considered positive when any presence of bacteria was detected at x40 magnification. The method of sample taking was also recorded. RESULTS: Of 18,302 consultations of children younger than 15 years, 1173 (6.4%) needed both a urine culture and a urine microscopy. Urine cultures demonstrated that 20.9% of the samples were consistent with the diagnosis of UTI. Bacteriuria and leukocyturia tests had a sensitivity of 87.4% (95% CI, 82.7%-91.0%), a specificity of 94.8% (95% CI, 93.2%-96.1%), a likelihood ratio for a positive test of 16.7 (95% CI, 16.18-17.61), and a likelihood ratio for a negative test of 0.13 (95% CI, 0.12-0.14). Samples taken by sterile methods (suprapubic aspiration and bladder catheterization) had a better positive predictive value than those taken by nonsterile methods (urine bag and midstream clean-catch) without having an adverse impact on the negative predictive value. CONCLUSIONS: Urine microscopy without Gram stain is a good test for predicting the presence of UTIs in children, which supports the use of this screening method in pediatric emergency units.

Adolescent↗
PubMed1975

Uriglox and quantitative urine microscopy in diagnosis of urinary tract infection.

The aim of this study was to find an alternative to the sole use of abundant cultural findings as a basis for the diagnosis of urinary tract infection (UTI). For this purpose, the results obtained from the bacteriological culture of daytime urine specimens from 154 students by the dip slide method were checked against the findings from the quantitative culture, microscopy and Uriglox testing of the first morning urines voided later at home. As a diagnostic criterion, the finding of 10(5) or more bacteria/ml urine in two successive cultures had an error of 19%. For the simultaneous occurrence in the morning urine of abundant bacteria (larger than or equal to 10(5)/ml) and a subnormal glucose concentration (as revealed by the Uriglox test), this error was 1.5%. Only the latter combination showed, therefore, the presence of UTI at the confidence level of larger than or equal to 95%, or was "clinically significant". The specificity indices for the Uriglox test and the quantitative culture were 0.99 and 0.97, respectively. Microscopy of the morning urine showed 10(3) or more bacteria/ml in all the subjects with infection but the number of leucocytes was normal in a fifth of them. The specificity indices for microscopic counts of 10(3) or more organisms/ml and 10 or more leucocytes/mm3 were 0.74 and 0.94, respectively. For higher counts, i.e. 10(5) or more bacteria/ml and 50 or more leucocytes/mm3, the specificity index of positive microscopy was 1.0. This specificity level was, however, attained at the expense of the sensitivity, which for 10(5) or more organisms/ml was 0.67 and for 50 or more leucocytes/mm3 0.53. It is concluded that abundant bacterial contamination of specimens often decisively complicates the diagnostic use of urine culture, and therefore the combined use of quantitative culture, microscopy and the Uriglox test is recommended as the principal tool for the diagnosis of UTI in ordinary hospital and ambulatory health services.

Female↗
PubMed2005

Characterization of sectioning fluorescence microscopy with thin uniform fluorescent layers: Sectioned Imaging Property or SIPcharts.

Thin, uniformly fluorescing reference layers can be used to characterize the imaging conditions in confocal, or more general, sectioning microscopy. Through-focus datasets of such layers obtained by standard microscope routines provide the basis for the approach. A set of parameters derived from these datasets is developed for defining a number of relevant sectioned imaging properties. The main characteristics of a particular imaging situation can then be summarized in a Sectioned Imaging Property-chart or SIPchart. We propose the use of such charts for the characterization of imaging properties in confocal and multiphoton microscopy. As such, they can be the basis for comparison of sectioned imaging condition characteristics, quality control, maintenance or reproduction of sectioned imaging conditions and other applications. Such charts could prove useful in documenting the more relevant properties of the instrumentation used in microscopy studies. The method carries the potential to provide the basis for a general characterization of sectioned imaging conditions as the layers employed can be characterized and fabricated to standard specifications. A limited number of such thin, uniformly fluorescing layers is available from our group for this purpose. Extension of the method to multiphoton microscopy is discussed.

Journal Article↗
PubMed2006

Crystallography of dispersed liquid crystalline phases studied by cryo-transmission electron microscopy.

Low molecular weight surfactants, for example monoglycerides and phospholipids, form a multitude of self-assembled structures, such as inverted cubic or hexagonal mesophases, if brought into contact with water/oil. These mesophases can be dispersed in water using adequate surface-active materials such as low molecular weight surfactants or surface active polymers. In order to use such mesophase particles for incorporating drugs and aromas, it is essential to determine their internal crystallographic structure and to understand their mechanism of stabilization. Cryo-transmission electron microscopy was used to investigate the internal structure of different dispersed particles at various temperatures and oil contents. It is shown here that cryo-transmission electron microscopy, in combination with fast Fourier transform and tilting experiments, is effective in obtaining information on crystallographic structure, space group and morphology of particles with reversed bicontinuous cubic and hexagonal structures. In particular, using the presence or the absence of the {111} reflections and viewing the same particle under different axes of observation allows one to discriminate between the Im3m and Pn3m space groups. A major advantage of cryo-transmission electron microscopy is the ability to analyse single particles. This allows the identification of particles present at very low concentrations and the coexistence of particles with different internal self-assembly structures. With this technique we have obtained strong evidence for the presence of two cubic internal self-assembly structures with different space groups within the same dispersion. In addition, we found that cryo-transmission electron microscopy combined with tilting experiments enables the analysis of internal particle morphology, allowing the discussion of mechanisms for hexosome stabilization.

Journal Article↗
PubMed2006

Crystallization of poly(L-lactid acid) monitored by dielectric relaxation spectroscopy and atomic force microscopy.

An investigation was carried out on the crystallization process of poly(l-lactid acid) by dielectric relaxation spectroscopy and atomic force microscopy. Experimental results were generated by dielectric relaxation spectroscopy over a wide range of frequency and temperature in both the wholly amorphous state and during crystallization. The variation of the average relaxation time was studied during crystallization at 80 degrees C and the temperature dependence of this relaxation time for wholly amorphous and crystallized samples was analysed. This behaviour was modelled by Havriliak-Negami and Vogel-Fulcher equations. The sensitivity of the segmental dynamics to the degree of crystallinity was analysed, taking into account the relaxing segments and the thickness of the amorphous layer between lamellae. The morphologies obtained during crystallization processes at 80, 130 and 150 degrees C were monitored by atomic force microscopy at both the lamellar level and by analysing the multilayered superstructures formed. Hedrites, intermediate structures between single lamellar crystals and mature spherulites, were found to appear at the highest temperatures, whereas no evidence of hedrites was found at 80 degrees C, the spherulites seemed to be constructed from a framework of individual dominant lamellae that splay apart and branch. Complementary to the atomic force microscopy study, the evolution of the obtained morphologies was also followed by optical microscopy. Supporting evidence about the thermal behaviour of the polymers was obtained with differential scanning calorimetry.

Journal Article↗
PubMed1979

Desmoplastic malignant melanoma: study of a case by light and electron microscopy.

This article is a study by light and electron microscopy of a case of desmoplastic malignant melanoma that attempts to resolve the conflict in views regarding the nature of the cells responsible for the desmoplasia associated with this clinico-pathologic entity. On the basis of evidence presented, it is concluded that the cells are dedifferentiated cells of the malignant melanoma with fibroblastic features and probably fibroblastic functions rather than host-engendered fibrolbasts in response to invasive melanoma. The evidence consists of the finding of macular desmosomes between those cells, a feature previously noted in amelanotic and melanotic melanomas, the finding of others by electron microscopy of fibroblast-like cells in spindle-cell squamous carcinomas, and the finding by light microscopy of features of vascular invasion of the malignancy. That the diagnosis of this variant of malignant melanoma by pattern can be made by light microscopy is reaffirmed.

Aged↗
PubMed1984

Persistence of Nosema locustae Spores in Soil as Determined by Fluorescence Microscopy.

Nosema locustae, a protozoan parasite of grasshoppers, is used as a bioinsecticide. In the present study, the persistence of N. locustae spores in soil and the interaction of these spores with the indigenous soil microflora were examined with various forms of microscopy and staining. Fluorescence microscopy was found to be better than phase-contrast or bright-field microscopy for detecting and viewing spores in soil. Fluorescein isothiocyanate was a better fluorescent stain than acridine orange or fluorescein diacetate; water-soluble aniline blue did not stain spores. The eight bright-field microscopy stains tested (phenolic erythrosin, phenolic rose bengal, malachite green, crystal violet, safranin, Congo red, methyl red, and eosin B) were not satisfactory, as spore staining characteristics were either poor or masked by overstained soil debris. A procedure was developed which allowed spores to be extracted from soil with a peptone-phosphate buffer, recovered on a membrane filter, and stained with fluorescein isothiocyanate for microscopic counting. This procedure was used to assess the persistence of N. locustae spores in field and laboratory soils. The number of N. locustae spores in a laboratory model soil system persisted at a high level for over 8 weeks when the soil was incubated at 5 degrees C but exhibited a 1,000-fold decrease after 1 week of incubation at 27 degrees C. Persistence was related to the temperature-dependent activity of the indigenous soil microflora, which, on the basis of microscopic observations, appeared to prey on N. locustae spores. N. locustae spores were detected in an N. locustae-treated field soil at a low level consistent with the level for laboratory soil incubated at 27 degrees C, and they persisted at this level for over 2 months. No spores were detected on vegetation from this field or in the soil from an adjacent, nontreated control field. N. locustae-like spores were also detected in soil from nontreated fields supporting large grasshopper populations.

Journal Article↗
PubMed1984

Value of urine microscopy in predicting histological changes in the kidney: double blind comparison.

Fresh, first morning specimens of urine from 22 consecutive patients were examined by quantitative microscopy on the morning of renal biopsy; the renal biopsy samples were evaluated "blindly." Five patients showed no abnormality in the biopsy samples but eight had minimal, one mild, six moderate, and two severe histological changes. Comparison of the results of quantitative microscopy of urine with the presence or absence of histological evidence of disease showed that sensitivity was 88%, specificity 83%, accuracy 86%, positive predictive value 93%, and negative predictive value 71%. When combined with microscopy of a second urine specimen these values were 100%, 50%, 87%, 85%, and 100% respectively. There was a significant relation between number of casts and severity of the histological changes (p less than 0.01). Comparison of renal functional abnormalities with histological findings gave values of 64%, 100%, 73%, 100%, and 50% respectively. It is concluded that quantitative microscopy of the first morning specimen of urine is a sensitive test with high predictive value for the presence or absence of renal disease. If no casts are detected in two early morning specimens the likelihood of finding anything more than minimal changes in a biopsy sample is virtually zero.

Biopsy↗
PubMed1982

Comparison of culture and microscopy in the diagnosis of Gardnerella vaginalis infection.

A comparison was made between human blood agar containing amphotericin B, nalidixic acid and either gentamicin or colistin for the isolation of Gardnerella vaginalis from cases of non-specific vaginitis seen in a clinic for sexually transmitted diseases. The medium containing gentamicin was more inhibitory for non-Gardnerella species, but not sufficiently inhibitory to allow direct plating in the clinic without spreading for single colonies. The diffuse beta haemolysis produced by G vaginalis on human, but not on horse blood agar, proved very useful in differentiating it from other vaginal organisms and was not affected by the antibiotics used. This characteristic, together with Gram stain morphology, oxidase and catalase, provides a simple, reliable methods of identifying G vaginalis. Sixty women with symptoms of vaginitis, in whom no other pathogen was isolated, were examined by culture and microscopy. Gardnerella vaginalis was grown from 45 whereas only 31 had positive microscopy (clue cells or Gram-variable bacilli). There was no significant difference between the rate of isolation of G vaginalis in the group with positive microscopy (25/31) and that with negative microscopy (20/31).

Anti-Bacterial Agents↗