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At least 19 recordsLinked to original sources
PubMed1989

Characterization of exposure to molds and actinomycetes in agricultural dusts by scanning electron microscopy, fluorescence microscopy and the culture method.

Air samples from 79 farms with 10(5) to 10(11) microorganisms/m3 were analyzed by scanning electron microscopy (SEM), fluorescence microscopy (FM), and the culture method. The total exposure to microorganisms (particularly actinomycetes) was underestimated when assessed as colony-forming units (cfu). The average cfu count was one-sixth of the total count according to SEM or FM, and the individual variability was great. This occurrence was partly explained by the aggregation of spores. Single spores accounted for 2-65% of all spores in 35 samples. There was an average of three spores/particle, and 93 (range 67-100)% of the spores were single or in aggregates of respirable size. Aggregation was more pronounced for actinomycetes and at high spore counts. Actinomycetes and bacteria could not be distinguished by FM. Bacteria (other than actinomycetes) were not detected by SEM, yet the total count of microorganisms was similar for FM and SEM. Most particles were spores from actinomycetes and fungi of the genera Aspergillus or Penicillium.

Actinomycetales↗
PubMed1992

Opposite effect between intercalator and minor groove binding drug on the higher order structure of DNA as is visualized by fluorescence microscopy.

Fluorescence microscopy is applied to obtain the information on the change of the higher-order structure of giant DNA molecules in an aqueous solution. Using T4 DNA, it becomes clear that ethidium bromide, an intercalator, tends to extend the DNA, whereas minor groove binding drugs such as 4',6-diamidino-2-phenylindole and Hoechst 33258 tend to contract the DNA. These changes of higher-order structure have been quantitatively evaluated as the changes in persistent length together with the change of contour length. It is also confirmed that the persistent length obtained by use of fluorescence microscopy is reliable enough comparing with those reported for the shorter DNA by use of light scattering.

Bacteriophage T4↗
PubMed1996

Fluorescence lifetime imaging: an emerging technique in fluorescence microscopy.

Fluorescence microscopy is an important tool for biological research, in part because of the extremely high detection sensitivity that can be achieved, but also because fluorescent molecules can be used as probes on account of their environmental responsiveness, for example to measure intracellular pH or metal ion concentration. Unfortunately, the environmental sensitivity can sometimes be a source of problems because of enhancement or 'quenching', which can make it very difficult to relate emission intensity to the amount of fluorophore present. The measured intensity is essentially proportional to the product of the amount of fluorophore present in the sample and the local quantum yield of the fluorophore (the quantum yield can be thought of as the probability that an excited molecule decays by fluorescence emission rather than by other non-radiative processes). This is a particular difficulty in an environment such as a cell or tissue slice in which quantum yield and flurophore concentration can both vary within the sample. Ideally we would wish to be able to measure the quantum yield of fluorescence as well as the fluorescence intensity, as this would allow environmental effects to be compensated for. Unfortunately, this is not at all easy, and indirect means to achieve the same goal are more appropriate. A recently introduced technique, fluorescence lifetime imaging (Morgan et al. 1992, Wang et al. 1992), offers one such means to improve quantification of fluorescence microscopy. In addition, as will be explained, the technique offers the prospect of significantly improving detection sensitivity in appropriate circumstances.

Energy Transfer↗
PubMed1999

Extended resolution fluorescence microscopy.

Fluorescence microscopy is an essential tool of modern biology, but, like all forms of optical imaging, it is subject to physical limits on its resolving power. In recent years, several exciting techniques have been introduced to exceed these limits, including standing wave microscopy, 4Pi confocal microscopy, I5M and structured illumination microscopy. Several such techniques have been definitively demonstrated for the first time during the past year.

Animals↗
PubMedDate not supplied

Which sites react first? Functional site distribution and kinetics on solid supports investigated using confocal Raman and fluorescence microscopy.

Fluorescence microscopy is a powerful technique for analyzing beads with very low loadings of fluorophores; however, the method is flawed when looking at more highly loaded beads as a result of severe problems with absorption. To probe distributions at higher loading levels, Raman spectroscopy avoids many of these issues. These studies show that there is a uniform distribution of reactive sites throughout the beads but that the spatial distribution of reacted sites depends on the polymer type, with a fine balance between reaction and diffusion rate.

Binding Sites↗
PubMed1981

FITC-dextran tracers in microcirculatory and permeability studies using combined fluorescence stereo microscopy, fluorescence light microscopy and electron microscopy.

Coupling fluorescein-isothiocyanate to dextrans (FITC-D) extends the usefulness of the dextrans as electron microscopic tracer particles by permitting preceding fluorescence stereo microscopy and high-power light microscopy of the tissue specimens. The fate of the tracer may thus be studied in vivo during the experiment, during fixation, and during the succeeding tissue processing. A study of some simple physicochemical characteristics of the tracer, and the influence, if any, of the fixing agent are also made possible. FITC-D was found to be uncharged in the pH range from 6.5 to 8.5, more rapidly precipitated by acetone than by alcohol, and to react with glutaraldehyde and osmium tetroxide in an unknown way during tissue fixation. FITC-D with molecular weights 70,000 and 150,000 showed no signs of diffusion during tissue preparation with the methods reported in the paper, whereas FITC-D 40,000 did so to a slight degree, when the tissue was kept for several days in the fixative vehicle. Securing the preservation of the lower molecular weight FITC-Ds during tissue fixation and preparation is more difficult and the described methods are not adequate. Dextrans provoke an anaphylactic reaction in most rat strains, but are well tolerated by Wistar Furth rats. The introduction of FITC into the dextran molecule might alter the biological reactions, but was also well tolerated by Wistar Furth rats. Combined fluorescence stereo microscopy, fluorescence microscopy of sections, light microscopy of strained sections and electron microscopy made it possible to follow a particular microcirculatory area, selected in vivo, to the final study in the electron microscope.

Animals↗
PubMed1973

Differences in the urea-extracted proteins of mouse epidermis and squamous cell carcinomata determined by fluorescence microscopy.

Fluorescence microscopy was used to demonstrate differences in the urea-extractable antigens of mouse epidermis and squamous cell carcinoma. When serum- and normal tissue sediment-absorbed antisera prepared against mouse epidermal urea-extracted proteins were further absorbed with carcinoma urea antigens, antisera specific for epidermis resulted. When antisera raised against the urea-extractable proteins of mouse squamous cell carcinomata were serum- and normal tissue sediment-absorbed and then further absorbed with epidermal urea antigens, antisera were prepared which stained papilloma and carcinoma, but not epidermis, and thus these antisera were not specific for carcinoma. Antisera prepared against the urea-extractable proteins of human epidermis reacted in immunodiffusion in agar with the epidermal urea proteins, but not with human squamous cell carcinoma urea proteins. Also antisera prepared against the carcinoma urea-extractable proteins reacted with these proteins in agar, but no reaction occurred with the epidermal urea-extractable proteins.

Absorption↗
PubMed1997

Applications of confocal and fluorescence microscopy.

Fluorescence microscopy has become a powerful tool for both the localization of cellular components in fixed cells, using target-specific fluorescent probes and labeled antibodies, and the fluorescence imaging of ions in single living cells. Despite its markedly lower spatial resolution when compared with electron microscopy, the essentially non-invasive nature of light microscopy provides a unique tool for examining cell behaviour at the level of the single cell bringing new insight into both cellular heterogeneities and cell-cell interactions. Further developments in both fluorescent probes and instrumentation should provide even more powerful tools to probe the mechanisms of cell function, both in vitro and in vivo.

Animals↗
PubMed1999

Platelet-derived microparticles on synthetic surfaces observed by atomic force microscopy and fluorescence microscopy.

Platelet activation on a thrombogenic surface includes the release of membrane-derived microparticles that provide catalytic sites for blood coagulation factors. Here, we describe a quantitative investigation on the production and dimensions of platelet-derived microparticles observed on glass and polyethylene under aqueous conditions, using atomic force microscopy (AFM) and complementary fluorescence microscopy. The results show that contact-activated platelet microparticles are not evenly distributed over a thrombogenic surface, but in clusters in close proximity to adherent platelets. The microparticles are localized near the platelet periphery, and in some cases appear to emanate from platelet pseudopodia, suggesting that formation may result from vesiculation of the pseudopodia. The microparticles measured 125 +/- 21 nm (n = 73) in the x-y dimensions and 5.2 +/- 3.6 nm in height. The results compared closely with 125 +/- 22 nm width and 4.1 +/- 1.6 nm height obtained for control preparations of thrombin activated microparticles, that were filtered and deposited on glass. Large differences between the measured widths and heights of adsorbed microparticles suggest that platelet microparticles may undergo spreading after attachment to a surface. The adsorbed microparticles expressed platelet membrane receptor GPIIb/IIIa, and many expressed the platelet activation marker P-selectin as determined by fluorescence microscopy. The high number distribution of procoagulant microparticles per unit area of surface compared with platelets suggests that platelet-derived microparticles provide a mechanistic route for amplifying thrombus formation on a thrombogenic surface.

Biocompatible Materials↗
PubMed1972

Identification of triploid genome by fluorescence microscopy.

Fluorescence markers on chromosome numbers 3, 13, and 14 gave cytological evidence of the paternal origin of the extra haploid set in a premature triploid infant with XXY sex chromosome complement. The mother had discontinued the use of oral contraceptives 13 months prior to conception. It is not possible to tell whether the mechanism involved was fertilization by dispermy or by a diploid sperm.

Abnormalities, Multiple↗
PubMed1998

Quantitative fluorescence resonance energy transfer measurements using fluorescence microscopy.

Fluorescence resonance energy transfer (FRET) is a technique used for quantifying the distance between two molecules conjugated to different fluorophores. By combining optical microscopy with FRET it is possible to obtain quantitative temporal and spatial information about the binding and interaction of proteins, lipids, enzymes, DNA, and RNA in vivo. In conjunction with the recent development of a variety of mutant green fluorescent proteins (mtGFPs), FRET microscopy provides the potential to measure the interaction of intracellular molecular species in intact living cells where the donor and acceptor fluorophores are actually part of the molecules themselves. However, steady-state FRET microscopy measurements can suffer from several sources of distortion, which need to be corrected. These include direct excitation of the acceptor at the donor excitation wavelengths and the dependence of FRET on the concentration of acceptor. We present a simple method for the analysis of FRET data obtained with standard filter sets in a fluorescence microscope. This method is corrected for cross talk (any detection of donor fluorescence with the acceptor emission filter and any detection of acceptor fluorescence with the donor emission filter), and for the dependence of FRET on the concentrations of the donor and acceptor. Measurements of the interaction of the proteins Bcl-2 and Beclin (a recently identified Bcl-2 interacting protein located on chromosome 17q21), are shown to document the accuracy of this approach for correction of donor and acceptor concentrations, and cross talk between the different filter units.

Animals↗
PubMed1987

Cell surface characteristics and DNA content of macrophages in murine bone marrow cultures. A study using simultaneous scanning electron microscopy and fluorescence microscopy.

An instrument combining scanning electron microscopy (SEM) and light microscopy (LM) was used to study the cell surface characteristics and DNA content of macrophages in murine bone marrow cultures. After a quantitative Feulgen DNA staining, the DNA content of the individual macrophages was measured and their cell surface morphology was studied immediately thereafter with the SEM part of the instrument. The cells were divided into six groups according to the number of microvilli and/or microridges present on their surface. A proportion of macrophages showed a DNA content more than occurs in diploid cells, which could indicate a future division. No special surface morphology could be detected in this cell type.

Animals↗