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Results for “Microscopy, Ultraviolet”

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At least 1,063 records · Page 59Linked to original sources
PubMedDate not supplied

[Modification of the lipid component of bacterial membranes by the introduction of lipotropic compounds into lyophilized cells].

In order to elucidate potentialities of modifying the lipid component of bacterial membranes, lyophilized cells of M. lysodeikticus, E. coli and other bacteria were treated by hydrophobic compounds dissolved in the organic solvent, with the latter subsequently removed by evaporation or freezedrying prior to cell rehydration. The data obtained by means of spin-probes, fluorescent spectroscopy, electron microscopy, photoreactive label and other methods suggest that following bacteria rehydration at least part of the substance occurs in the membrane structures. The amount of the substance involved in bacterial cells depends on the type of compound and on whether bacterial cells belong to gram-positive or gram-negative microorganisms: the substance content of the latter is greater than of the former.

Escherichia coli↗
PubMedDate not supplied

[Early histologic diagnosis of acute myocardial infarct by autofluorescence. Evaluation in humans and experimental animals].

The value of an autofluorescence method for the early diagnosis of myocardial infarction was evaluated in humans and experimental animals. The hearts from 15 rats and 18 dogs that had undergone coronary occlusion, and those obtained from 29 human autopsy cases with clinical evidence of myocardial infarction were studied. Routine and frozen sections stained and unstained were observed under fluorescence microscopy. In all the cases, ischemic areas exhibited fibres with a bright yellow autofluorescence. There was some variations in fluorescence intensity from routine stained and unstained to frozen stained and unstained sections. These results demonstrate that the fluorescence method can be used to defect early myocardial ischemic injury. The intracellular alterations induced by ischemia could be responsible for light absorption and thus characteristic autofluorescence.

Animals↗
PubMed1981

A high vacuum photoelectron microscope for the study of biological specimens.

A photoelectron microscope (photoemission electron microscope) has been designed and built for the study of organic and biological samples. The microscope is an oil-free stainless steel high vacuum instrument pumped by a titanium sublimation pump, an ion pump, and molecular sieve roughing pumps. The electron lenses are of the electrostatic unipotential type. The microscope is equipped with a dewar for sample cooling, an internal cryogenic camera, TV-image intensifier, and vibration isolation support. Applications include studies of biological cell surfaces, photosynthetic membranes and aromatic chemical carcinogens. A representative micrograph of mouse 3T3 cells is included. In some respects, photoelectron micrographs resemble scanning electron micrographs, but the basis for contrast is different in these two techniques.

Animals↗
PubMed1993

Evidence that the CryIA crystal protein from Bacillus thuringiensis is associated with DNA.

Toxin generated by activation of the Bacillus thuringiensis CryIA(c) crystal protein (protoxin) with bovine trypsin was separated into two components by anion-exchange chromatography. One component (T2) was DNA-associated toxin, and the other was the DNA-free toxin (T1). Only one major protoxin component was observed, and it was found to be associated with DNA. The DNA from the T2 toxin varied in size from 100 to 300 base pairs, whereas the crystal and the solubilized protoxin contained 20-kilobase DNA as the major DNA component. DNase treatment converted the T2 toxin to the DNA-free T1 toxin. In contrast, the DNA in the crystal and the solubilized protoxin was resistant to DNase digestion and was not dissociated from the protein by 1.5 M NaCl. The protoxin and DNA appeared to elute as a complex with a molecular mass of > 2 x 10(6) Da on gel-filtration chromatography. No toxin was generated from the protoxin with trypsin after extensive digestion of the protoxin with DNase or dissociation of the DNA by succinylation of the lysine residues. It is proposed that DNA binds to the COOH-terminal half of the crystal protein and is essential for maintaining the conformational integrity required for crystal formation and generation of toxin.

Bacillus thuringiensis↗
PubMed1995

[Cyclosporin A and the permeability of the cytoplasmic membrane in Aspergillus niger].

Cyclosporine A was shown to impair selective permeability of cytoplasmic membranes in Aspergillus niger thus inducing leakage of low molecular components of the intracellular fond from the cells. In this respect lyposomal cyclosporine had a more pronounced action than the free form. Cyclosporine was compared with amphotericin B and the latter in the free and lyposomal forms demonstrated a higher effect on the cell membranes of Asp. niger. In combination with amphotericin B cyclosporine markedly stimulated the effect of amphotericin B on permeability of the cell membranes.

Amphotericin B↗
PubMed1996

Two-photon excited lifetime imaging of autofluorescence in cells during UVA and NIR photostress.

By monitoring coenzyme autofluorescence modifications, as an indicator of cell damage, the cellular response to femtosecond near-infrared (NIR) radiation (two-photon absorption) was compared with exposure to low-power UVA radiation (one-photon absorption). Excitation radiation from a tunable Ti-sapphire laser, focused through high-numerical-aperture microscope optics, provided diffraction-limited microbeams of an adjustable peak power. Laser scanning NIR microscopy was used to detect spatially the intracellular distribution of fluorescent coenzymes by fluorescence intensity imaging as well as fluorescence lifetime imaging (tau-mapping). Upon the onset of UV or NIR exposure, Chinese hamster ovary cells exhibited blue/green autofluorescence with a mean lifetime of 2.2 ns, which was attributed to NAD(P)H in mitochondria. Exposure to 365 nm radiation from a high-pressure mercury lamp (1 mW, 300 J cm-2) resulted in oxidative stress correlated with increased autofluorescence intensity, onset of nuclear fluorescence, and a fluorescence lifetime decrease. The cellular response to femtosecond NIR microbeams depended significantly on peak power. Peak powers above a threshold value of about 0.5 kW (average power: 6 mW). 0.55 kW (7 mW) and 0.8 kW (10 mW) at 730 nm, 760 nm and 800 nm, respectively, resulted in the onset of short-lived luminescence with higher intensity (100 x) than the intracellular NAD(P)H fluorescence. This luminescence, accompanied by destruction of cellular morphology, was localized and occurred in the mitochondrial region. In contrast, beams at a power of less than 0.5 kW allowed nondestructive fluorophore detection with high spatial and temporal resolution without modification of cellular redox state or cell morphology.

Animals↗
PubMed1994

A scanning electron microscope study of the pecten oculi of the black kite (Milvus migrans): possible involvement of melanosomes in protecting the pecten against damage by ultraviolet light.

The pecten oculi of the black kite (Milvus migrans), a diurnally active bird of prey, has been examined by scanning electron microscopy. In this species the pecten consists of 12 highly vascularised pleats, held together apically by a heavily pigmented 'bridge' and projects freely into the vitreous body in the ventral part of the eye cup. Ascending and descending blood vessels of varying calibre, together with a profuse network of capillaries, essentially constitute the vascular framework of the pecten. A distinct distribution of melanosomes is discernible on the pecten, the concentration being highest at its apical end, moderate at the crest of the pleats and least at the basal and lateral margins. Overlying and within the vascular network, a close association between blood vessels and melanocytes is evident. It is conjectured that such an association may have evolved to augment the structural reinforcement of this nutritive organ in order to keep it firmly erectile within the gel-like vitreous. Such erectility may be an essential prerequisite for its optimal functioning, as well as in its overt use as a protective shield against the effects of ultraviolet light, which otherwise might lead to damage of the pectineal vessels.

Animals↗
PubMed2001

UVB irradiation suppresses cytokine production and innate cellular immune functions in mice.

We examined whether ultraviolet-B (UVB) irradiation (6 kJ/m2) alters cytokine production and other innate immune reactions by murine peritoneal macrophages and peripheral neutrophils. Along with these experiments, serum IgG levels were also assessed. In addition, using scanning electron microscopy (SEM) we observed macrophages that had been exposed to UVB in vitro. Results showed that UVB irradiation: (1) decreased IL-12 production while increasing IL-1alpha secretion from macrophages, but had no effect on IL-1alpha from neutrophils; (2) suppressed phagocytosis of macrophages but not of neutrophils; (3) diminished active oxygen production of macrophages but not of neutrophils; (4) had no effect on serum IgG levels; and (5) caused significant cell destruction of macrophages in vitro. These results suggested: (1) that UVB irradiation could induce characteristic suppression of innate immunity; (2) that innate cellular immunity was more susceptible to the effects of UVB irradiation than humoral immunity.

Animals↗
PubMed1977

Comparison of intestinal (Illinois strain) and cell culture-adapted (M-HP strain) viral populations of transmissible gastroenteritis of swine.

Intestinal and cell culture-adapted viral populations of transmissible gastroenteritis (TGE) of swine were compared by means of sucrose gradient centrifugation, immunnofluorescence, electron microscopy, immune electron microscopy, statistical analysis of the number of plaque-forming units, and ultraviolet sensitivity. Results indicated that the size range and general coronavirus morphologic characteristics were shared by both viral populations. Marked morphologic variations existed among particles from both populations. Unlike the cell culture-adapted virus, the Illinois virus of intestinal origin was infractions representing 2 bands of infectivity which were isolated by the sucrose gradient centrifugation method. The intestinal and cell culture-adapted TGE viruses were similar in antigenicity and in sensitivity to ultraviolet irradiation. There was no indication of a 2nd virus in addition to the coronavirus described as the cause of TGE.

Animals↗
PubMed2002

Delivery of plasmid DNA to articular chondrocytes via novel collagen-glycosaminoglycan matrices.

Our primary objective was to fabricate a porous gene-supplemented collagen-glycosaminoglycan (GSCG) matrix for sustained delivery (over a period of several weeks) of plasmid DNA to articular chondrocytes when implanted into cartilage lesions. The specific aims of this in vitro study were to determine the release kinetics profiles of plasmid DNA from the GSCG matrices, and to determine the ability of the released plasmid DNA to transfect adult canine articular chondrocytes. In particular, we evaluated the effects of two variables, cross-linking treatment and the pH at which the DNA was incorporated into the matrices, on the amount of the plasmid DNA that remained bound to the GSCG matrices after passive (nonenzymatic) leaching and on the expression of a reporter gene in articular chondrocytes grown in the GSCG matrices. Collagen-glycosaminoglycan matrices were synthesized without cross-linking, and by three cross-linking treatments: dehydrothermal (DHT) treatment, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) treatment, and exposure to ultraviolet (UV) radiation. The plasmid DNA was incorporated into the collagen-glycosaminoglycan matrices in solutions at pH 2.5 or 7.5. Transmission electron microscopy studies revealed plasmid DNA bound to the walls of the porous GSCG matrices. In general, the GSCG matrices fabricated at pH 2.5 retained a larger fraction of the initial DNA load after 28 days of incubation in Tris-EDTA buffer. The passive, solvent-mediated release of the plasmid DNA from the GSCG matrices showed a biphasic pattern consisting of a faster, early release rate over the initial 8 hr of leaching followed by a slower, late release rate that was relatively constant over the subsequent 28 days of leaching. Electrophoretic analyses revealed that the plasmid DNA released from the GSCG matrices fabricated at pH 2.5 had been linearized and/or degraded; whereas the plasmid DNA leached from the GSCG matrices prepared with a DNA solution at pH 7.5 was primarily supercoiled and linear. Plasmid DNA released from all GSCG matrix formulations was able to generate luciferase reporter gene expression in monolayer-cultured chondrocytes transfected with the aid of a commercial lipid reagent, and in chondrocytes cultured in the GSCG matrices without the aid of a supplemental transfection reagent. Luciferase expression in chondrocyte-seeded GSCG constructs was evident throughout the culture period (28 days), with the EDC and UV cross-linked matrices prepared at pH 7.5 providing the highest transgene expression levels. We conclude that released plasmid DNA continually transfected canine articular chondrocytes seeded into GSCG matrices in vitro for a 4-week period as evidenced by luciferase reporter gene expression. Thus, GSCG matrices can be fabricated to provide sustained release of plasmid DNA carrying a potential therapeutic gene.

Animals↗
PubMed2006

Quantification of parthenolide in Tanacetum species by LC-UV/LC-MS and microscopic comparison of Mexican/US feverfew samples.

LC-UV and LC-MS methods have been developed which permit the analysis of parthenolide in different Mexican/US feverfew samples and commercial products. The study was undertaken to confirm the presence of parthenolide in Mexican plant samples and its comparison with US feverfew samples. The best results were obtained with a Phenomenex Luna C18 (2) column using gradient mobile phase of water and acetonitrile:methanol (9 : 1). Elution was run at a flow rate of 1.0 mL per min and ultraviolet detection at 210 nm. The results obtained using LC-UV were comparable to those obtained using LC-MS. Parthenolide was detected in all the samples analyzed and is the major chemical constituent of feverfew. The samples collected in Oaxaca, Mexico (0.28%) and Puebla, Mexico (0.25%) showed the highest content of parthenolide. All Parthenium samples were also examined under light and fluorescent microscopy.

Anti-Inflammatory Agents, Non-Steroidal↗