PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Microscopy, Ultraviolet”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 451 records · Page 25Linked to original sources
PubMed1979

Photoelectron emission microscopy of biological tissue; the influence of glutaraldehyde and heavy or biligrafin on the emission image of chicken liver in methacrylate.

The effect of various preparations on the emission image was studied taking into account the influence of UV wave length, section thickness and specimen support. By suitable selection of these parameters, images with sufficient contrast can be obtained of unstained specimens which are only fixed with glutaraldehyde. With glutaraldehyde fixation intravitally injected Biligrafin used as a stain in cholecystography is recognized in the emission image of liver tissue labeling the intravital transport path from the blood capillaries to the bile ducts. Hypotheses for the image forming process are discussed.

Aldehydes↗
PubMed1999

Development of sub-micron patterned carbon electrodes for immunoassays.

Sub-micron sized domains of a carbon surface are derivatized with antibodies using biotin/avidin technology. These sites are spatially-segregated from, and directly adjacent to, electron transfer sites on the same electrode surface. The distance between these electron transfer sites and enzyme-loaded domains are kept to a minimum (e.g. less than a micron) to maintain the high sensitivity required for the measurement of enzyme-linked cofactors in an enzyme-linked immunoassay (ELISA). This is accomplished through the use of photolithographic attachment of photobiotin using an interference pattern from a UV laser generated at the electrode surface. This allows the construction of microscopic arrays of active ELISA sites on a carbon substrate while leaving other sites underivatized to facilitate electron transfer reactions of redox mediators; thus maximizing sensitivity and detection of the enzyme mediator. The carbon electrode surface is characterized with respect to its chemical structure and electron transfer properties following each step of the antibody immobilization process. The characterization of specific modifications of micron regions of the carbon surface requires analytical methodology that has both high spatial resolution and sensitivity. We have used fluorescence microscopy with a cooled CCD imaging system to visualize the spatial distribution of enzyme immobilization sites (indicated by fluorescence from Texas-Red labeled antibody) across the carbon surface. The viability of the enzyme attached to the surface in this manner was demonstrated by imaging the distribution of an insoluble, fluorescent product.

Alkaline Phosphatase↗
PubMed2000

Chronic lymphocytic leukemia lymphocytes lack the capacity to repair UVC-induced lesions.

Cells from chronic lymphocytic leukemia (CLL) patients and from healthy individuals were irradiated with UVC and incubated for varying periods of time. The number of single strand breaks and alkali-labile sites was determined by comet analysis. Unirradiated CLL and healthy cells exhibited no significant numbers of single strand breaks. The extent of DNA damage was found to increase with dose for both healthy and CLL cells. However, the CLL cells had much more extensive DNA fragmentation than healthy cells at each dose. Deoxyribonucleoside supplemented medium inhibited comet formation in both cell types. Thymidine alone produced the same effect. In healthy cells, repair of lesions was complete after 4 h of incubation as indicated by the absence of comet formation. The CLL cells exhibited no significant repair even after 48 h. CLL lymphocytes are killed by very low doses of UVC radiation. The results reported here suggest that this hypersensitivity results from the inability of CLL cells to repair UVC-induced DNA damage and a contributing factor is the low amounts of intracellular deoxyribonucleosides.

Comet Assay↗
PubMed2004

Self-assembled metal colloid films: two approaches for preparing new SERS active substrates.

In this paper, we propose two new approaches for preparing active substrates for surface-enhanced Raman scattering (SERS). In the first approach (method 1), one transfers AgI nanoparticles capped by negatively charged mercaptoacetic acid from a AgI colloid solution onto a quartz slide and then deoxidizes AgI to Ag nanoparticles on the substrate. The second approach (method 2) deoxidizes AgI to Ag nanoparticles in a colloid solution and then transfers the Ag nanoparticles capped by negatively charged mercaptoacetic acid onto a quartz slide. By transfer of the AgI/Ag nanoparticles from the colloid solutions to the solid substrates, the problem of instability of the colloid solutions can largely be overcome. The films thus prepared by both approaches retain the merits of metal colloid solutions while they discharge their shortcomings. Accordingly, the obtained Ag particle films are very suitable as SERS active substrates. SERS active substrates with different coverages can be formed in a layer-by-layer electrostatic assembly by exposing positively charged surfaces to the colloid solutions containing oppositely charged AgI/Ag nanoparticles. The SERS active substrates fabricated by the two novel methods have been characterized by means of atomic force microscopy (AFM) and ultraviolet-visible (UV-vis) spectroscopy. The results of AFM and UV-vis spectroscopy show that the Ag nanoparticles grow with the increase in the number of coverage and that most of them remain isolated even at high coverages. Consequently, the surface optical properties are dominated by the absorption due to the isolated Ag nanoparticles. The relationship between SERS intensity and surface morphology of the new active substrates has been investigated for Rhodamine 6G (R6G) adsorbed on them. It has been found that the SERS enhancement depends on the size and aggregation of the Ag particles on the substrates. Especially, we can obtain a stronger SERS signal from the substrate prepared by method 1, implying that for the metal nanoparticles capped with stabilizer molecules such as mercaptoacetic acid, the in situ deoxidization in the film is of great use in preparing SERS active substrates. Furthermore, we have found that the addition of Cl- into the AgI colloid solution changes the surface morphology of the SERS active substrates and favors stronger SERS enhancement.

Journal Article↗
PubMed1997

Comparison of two-photon excitation laser scanning microscopy with UV-confocal laser scanning microscopy in three-dimensional calcium imaging using the fluorescence indicator Indo-1.

Two-photon excitation laser scanning fluorescence microscopy (2p-LSM) was compared with UV-excitation confocal laser scanning fluorescence microscopy (UV-CLSM) in terms of three-dimensional (3-D) calcium imaging of living cells in culture. Indo-1 was used as a calcium indicator. Since the excitation volume is more limited and excitation wavelengths are longer in 2p-LSM than in UV-CLSM, 2p-LSM exhibited several advantages over UV-CLSM: (1) a lower level of background signal by a factor of 6-17, which enhances the contrast by a factor of 6-21: (2) a lower rate of photobleaching by a factor of 2-4; (3) slightly lower phototoxicity. When 3-D images were repeatedly acquired, the calcium concentration determined by UV-CLSM depended strongly on the number of data acquisitions and the nuclear regions falsely exhibited low calcium concentrations. probably due to an interplay of different levels of photobleaching of Indo-1 and autofluorescence, while the calcium concentration evaluated by 2p-LSM was stable and homogeneous throughout the cytoplasm. The spatial resolution of 2p-LSM was worse by 10% in the focal plane and by 30% along the optical axis due to the longer excitation wavelength. This disadvantage can be overcome by the addition of a confocal pinhole (two-photon excitation confocal laser scanning fluorescence microscopy), which made the resolution similar to that in UV-CLSM. These results indicate that 2p-LSM is preferable for repeated 3-D reconstruction of calcium concentration in living cells. In UV-CLSM, 0.18-mW laser power with a 2.6-phi pinhole (in normalized optical coordinate) gives better signal-to-noise ratio, contrast and resolution than 0.09-mW laser power with a 4.9-phi pinhole. However, since the damage to cells and the rate of photobleaching is substantially greater under the former condition, it is not suitable for repeated acquisition of 3-D images.

Animals↗
PubMed2003

A new system for laser-UVA-microirradiation of living cells.

Local nuclear irradiation of living cells has been used to gain insight into the dynamic changes that cell nuclei undergo in response to DNA damage. In particular, the effects of DNA double-strand breaks (DSBs), a major threat to the genomic integrity of cells, have been studied by local nuclear irradiation with ionizing radiation. This method has the disadvantage that it requires expensive equipment to generate a sufficiently high density of focused or collimated ionizing radiation. After appropriate sensitization of the cellular DNA, nuclear microirradiation with UVA can also produce DSBs. In this communication we present a semi-automatic system for laser-UVA-microirradiation based on a commercial laser scanning microscope. The system allows the convenient selection and precise irradiation of living cells, and could provide the basis for a more widespread availability of microirradiation facilities for DNA-repair research.

Calibration↗
PubMed2003

Study on DNA precipitation with a cationic polymer PAC (poly aluminuim chloride).

We studied on the interactions between DNA and polyaluminuimchloride (PAC) by ultraviolet spectroscopy and electron microscopy to understand the interaction between negative-charged macromolecules and PAC. Sodium ion seems to have only weak effect on the manner of DNA/PAC complex. However, acetate and phosphate anions competed against phosphate in DNA for interaction with PAC. It seems that negative macromolecule in a water system may be similar behavior with DNA under PAC.

Aluminum Chloride↗
PubMed2005

UV-A induces two calcium waves in Physcomitrella patens.

Our understanding of the role of Ca2+ in blue/UV-A photoreceptor signaling in a single cell is limited. Insight into calcium signaling has now been attained in Physcomitrella patens and its cryptochrome and phototropin knock-outs. Physcomitrella patens caulonemal filaments grow in the dark by apical extension and their apical cells are highly polarized. Fura-2-dextran ratio images of the apical cell from wild type (WT), Ppcry1a/1b and PpphotA2/B1/B2 were obtained immediately following UV-A exposure (30 microW cm(-2) at 340 nm for 1,000 ms plus 30 microW cm(-2) at 380 nm for 1,000 ms) [abbreviated as 1,000 ms (340/380 nm)] and demonstrated two intracellular waves: a Ca2+ wave from the growing apical tip through the apical cap, and a wave from the junction of the neighboring cell through the vacuolar, nuclear and plastid regions. In WT, the UV-A-induced tip wave increase had a magnitude of 454.0 +/- 40 nM, traveled at a rate of 3.4 +/- 0.7 microm s(-1) and was complete within 26.6 +/- 2.3 s, while the basal vacuolar wave had a magnitude of 596.8 +/- 110 nM, a rate of 8.4 +/- 0.8 microm s(-1) and duration of 25.3 +/- 4.9 s. Subsequent Ca2+ spikes of similar magnitude followed these waves. The amplitude of the Ca2+ waves in the apical cap and basal vacuolar regions of Ppcry1a/1b were higher than those in the WT, while the duration of those in PpphotA2/B1/B2 was longer. Subsequent Ca2+ spikes occurred in WT and Ppcry1a/1b but not in PpphotA2/B1/B2. When Mn2+ was added to the culture medium, the [Ca2+](cyt) increase was delayed, did not move as a wave and lasted longer. The results indicate that plants respond to blue light and UV-A radiation by generating a wave of changes in the [Ca2+](cyt). The characteristics of these Ca2+ waves were dependent upon cryptochrome and phototropin. Blue/UV-A signaling in P. patens appears to differ from that in Arabidopsis.

Bryopsida↗
PubMed1984

Visualization of pronuclei in living bovine zygotes.

Bovine embryos were surgically collected from the oviducts of superovulated crossbred heifers 48 h postonset of estrus. The one-celled ova were treated with 4'-6'-diamidino-2-phenylindole (DAPI) and observed under ultraviolet light by fluorescence microscopy. Both male and female pronuclei were visualized, identified and subjected to micromanipulation.

Animals↗
PubMed1991

In vitro inhibition of Helicobacter pylori urease: biochemical and ultrastructural analysis.

Inhibition of H. pylori urease was studied by means of electron-microscopy and electrophoretic methods using different urease inhibitors, such as acetohydroxamic-acid (AHA), L-ascorbic acid (AsA), copper ions, a combination of L-ascorbic acid with copper ions and UV light. AHA in two different concentrations and AsA at a concentration of 0.1 mg ml-1 showed incomplete inhibition of H. pylori urease activity in our electrophoretic experiments. Only membrane-bound activity was inhibited with AHA but not the activity localized within the cytoplasma as demonstrated by electron-microscopy. AsA at a concentration of 0.5 mg ml-1 and the combination of copper ions (1 microgram ml-1) with AsA completely inhibited the urease activity as demonstrated by electron-microscopy and electrophoretic experiments. Cu2+ ions in high concentrations (100 micrograms ml-1) and UV light exposure for more than 4 h induced a complete disintegration of H. pylori. Electrophoresis showed no active protein after UV light exposure of 2 h. Different urease inhibitors tested in this study showed dose-dependent inhibitory effects on H. pylori urease in vitro.

Ascorbic Acid↗
PubMed1991

Light sensitivity of methanogenic archaebacteria.

Representatives of four families of methanogenic archaebacteria (archaea), Methanobacterium thermoautotrophicum delta H, Methanobacterium thermoautotrophicum Marburg, Methanosarcina acetivorans, Methanococcus voltae, and Methanomicrobium mobile, were found to be light sensitive. The facultative anaerobic eubacteria Escherichia coli and Salmonella typhimurium, however, were tolerant of light when grown anaerobically under identical light conditions. Interference filters were used to show that growth of the methanogens is inhibited by light in the blue end of the visible spectrum (370 to 430 nm).

Euryarchaeota↗
PubMed1967

Autofluorescence of bone tissues.

The phenomenen of autofluorescence of bone is due primarily to the collagen itself rather than to incidental substances adsorbed on to it. Fluorescent microscopy is a convenient method of dating the different microanatomical components of bone, and in this respect the same conclusions can be reached from the study of microradiographs or autofluorescent photographs, which is proof of the intimate relation between the development of matrix and the progression of mineralization.

Bone Development↗
PubMed2005

Gold/palladium and silver/palladium colloids as novel metallic substrates for surface-enhanced Raman scattering.

New surface-enhanced Raman scattering (SERS) substrates, composed of gold or silver colloidal nanoparticles doped with palladium, were prepared. These novel colloids are stable and maintain a satisfactory SERS efficiency, even after long aging. The interest in doping the coinage metal nanoparticles with palladium is due to the well-known catalytic activity of this metal. Transmission electron microscopy (TEM) and ultraviolet-visible absorption spectroscopy were used to characterize the shape and size of the metal particles. It was found that these bimetallic colloidal nanoparticles have a core-shell structure, with gold or silver coated with palladium clusters.

Coated Materials, Biocompatible↗