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At least 829 records · Page 46Linked to original sources
PubMed1990

Two-photon laser scanning fluorescence microscopy.

Molecular excitation by the simultaneous absorption of two photons provides intrinsic three-dimensional resolution in laser scanning fluorescence microscopy. The excitation of fluorophores having single-photon absorption in the ultraviolet with a stream of strongly focused subpicosecond pulses of red laser light has made possible fluorescence images of living cells and other microscopic objects. The fluorescence emission increased quadratically with the excitation intensity so that fluorescence and photo-bleaching were confined to the vicinity of the focal plane as expected for cooperative two-photon excitation. This technique also provides unprecedented capabilities for three-dimensional, spatially resolved photochemistry, particularly photolytic release of caged effector molecules.

Animals↗
PubMed2003

Alterations in human epidermal Langerhans cells by ultraviolet radiation: quantitative and morphological study.

BACKGROUND: Ultraviolet (UV) exposure of human skin induces local and systemic immune suppression. This phenomenon has been well documented when UVB radiation (290-320 nm) is used. The mechanism is thought to involve Langerhans cells (LCs), the epidermal dendritic cells that play a crucial role in antigen presentation. A variety of studies have clearly demonstrated that UVB radiation decreases LC density and alters their morphology and immunological function, but little is known about the effects of the entire UV spectrum (ultraviolet solar simulated radiation, UV-SSR or UVB + UVA) or UVA (320-400 nm) radiation alone. OBJECTIVES: The purpose of this study was to analyse and compare the effects of a single exposure of human volunteers to UV-SSR, total UVA or UVA1 (340-400 nm) in the human epidermal LC density and morphology. METHODS: Immunohistochemistry on epidermal sheets with various antibodies and transmission electron microscopy (TEM) were used. RESULTS: Immunostaining for class II antigen revealed that a single UV-SSR exposure, corresponding to twice the minimal erythemal dose (MED), induced a significant reduction in LC density with only slight morphological alterations of remaining cells. After a single UVA exposure, LC density showed a dose-dependent reduction with a significant effect at 60 J cm(-2) (well above the MED). Moreover, the reduction of LC dendricity was also dose-dependent and significant for doses exceeding 30 J cm(-2). UVA1 radiation was as effective as total UVA for the later endpoint. As demonstrated by TEM, the location of Birbeck granules containing epidermal cells was modified in UVA-exposed areas. They were located in the spinous rather than in the suprabasal layer. In addition, the morphology of these cells was altered. We observed a rounding up of the cell body with a reduction of dendricity. Alterations of mitochondrial membrane and ridges were also seen. CONCLUSIONS: A single exposure of human skin in vivo to UV-SSR, UVA or UVA1 radiation results in different alterations of density and/or morphology of LCs. All these alterations may impair the antigen-presenting function of LCs leading to an alteration of immune response.

Adolescent↗
PubMed1991

Working with the confocal scanning UV-laser microscope: specific DNA localization at high sensitivity and multiple-parameter fluorescence.

The use of fast-staining DNA-specific dyes such as DAPI or Hoechst 33342/33258 has been a major problem for confocal scanning laser microscopy (CSLM) studies of intranuclear chromatin organization. Moreover, the availability of a confocal ultraviolet scanning laser microscope configuration, which allows an excitation at wavelengths of 364 nm as well as 488, 514 and 543 nm, is a prerequisite for single as well as multiple fluorescence parameter studies, especially if these studies are concerned with the precise localization of intranuclear signals. Here we report the characteristics and application of a CSLM, which was adapted for UV-excitation and therefore enables comparison of the spatial distribution of several types of signals within one preparation. In addition to multiple-parameter studies, we have also investigated the sensitivity of the system with regard to the identification of the double-stranded DNA of lampbrush chromosome loops in germinal vesicles of amphibian oocytes.

Animals↗
PubMed1980

Preparation of subviral particles from vaccinia virions irradiated with ultraviolet light.

Nucleoprotein complexes, containing proteins covalently bound to DNA, were prepared from vaccinia virions irradiated with ultraviolet light. In the electron microscope, these complexes were observed to have a spherical morphology with a densely staining central portion, apparently containing proteins cross-linked to DNA, from which loops or fibers of DNA or DNA complexed with protein emerged.

Chemical Phenomena↗
PubMed2004

Confocal fluorescence detection expanded to UV excitation: the first continuous fluorimetric assay of human steroid sulfatase in nanoliter volume.

Steroid sulfatase is an enzyme that currently enjoys considerable interest as a potential drug target in the treatment of estrogen- and androgen-dependent diseases, in particular breast cancer. We have purified human steroid sulfatase to apparent homogeneity from recombinant Chinese hamster ovary cells, and we established an assay with a new fluorogenic substrate, 3,4-benzocoumarin-7-O-sulfate (1). Substrate 1 features a K(m) value of 22.5 microM, which is close to the value for the natural substrate dehydroepiandrosterone sulfate (26 microM) and much lower than the K(m) values of other synthetic substrates (276-736 microM). Importantly, the cleavage of substrate 1 can be monitored continuously during the enzymatic cleavage, since a change in fluorescence intensity is detectable at the pH where the enzyme is active; in contrast, all other synthetic substrates described so far require alkalization to reveal a measurable absorbance or fluorescence signal. The adaptation of the assay to the 96-well format allows continuous monitoring of multiple wells in a microplate fluorescence reader. Applications of the assay for the determination of IC(50) and K(i) values of novel steroid sulfatase inhibitors are presented. Most importantly the assay was transferred to the nanoscale format (1-microl assay volume) in 2080-well plates with confocal fluorescence detection. This miniaturization will permit screening with a minimum throughput of 20000 compounds per day. The system presented demonstrates that the confocal detection platform used for nanoscreening can be successfully adapted to assays for which conventional ultraviolet dyes like coumarins are necessary. This strongly broadens the application range of confocal readers in drug screening.

Algorithms↗
PubMed1983

Estimation of the useful lifetime of polypropylene fiber in the anterior chamber.

A study of the stability of polypropylene fiber, size 4-0, to ultraviolet light was performed. Samples were radiated in physiological saline solution at 35.5 +/- 1.5 degrees C using a xenon-arc lamp at an intensity of 650 milliwatts per square centimeter. The light was filtered to remove wavelengths below 300 nanometers and thus simulated transmittance of the cornea. Tensile strength, elongation and modulus, and the surface morphology of the fiber by scanning electron microscopy (SEM) were determined as a function of exposure time. The average ultraviolet (UV) light intensity which irradiates the eye was determined from available meteorological data and was used to calculate human exposure at various geographical locations. This information along with the light energy of the xenon-arc lamp was used to calculate the useful lifetime of polypropylene fiber in the anterior chamber. Using an average exposure of 2.2 hours per day for a 60-year-old implant recipient, the useful lifetime ranges from 53 years in Miami, Florida, to 75 years in Seattle, Washington. Polypropylene loops from lenses which had been implanted in human eyes for up to 4.8 years showed no molecular degradation as compared to control material. Polypropylene fiber is therefore safe for use in anterior chamber implants.

Anterior Chamber↗
PubMed1993

Fluorescence of eosinophil leukocyte granules induced by the fluorogenic reagent 2-methoxy-2,4-diphenyl-3 (2H)-furanone.

The fluorogenic reagent MDPF forms highly fluorescent products specifically with primary amino groups (e.g., from lysine). Although widely used in analytical biochemistry, MDPF has infrequently been employed in cytochemical techniques for proteins. In this work, we describe the application of MDPF in fluorescence microscopy studies of horse, rat, and human blood cells. Under ultraviolet excitation, MDPF selectively induces an intense white-blue fluorescence reaction in the granules of eosinophil leukocytes, which contain strongly basic proteins. The advantages of MDPF for identification to reveal protein components in hematological cytochemistry are briefly discussed.

Animals↗
PubMed1977

Immunofluorescent studies of epidermal protein during UV induced carcinogenesis.

Previous studies with agar diffusion technique demonstrated that antibodies produced in rabbits by injection of urea extractable proteins of rat cornfied cells cross react with proteins extracted from normal epidermis of hairless mice using the same technique. In the present study we investigated by indirect immunofluorescence microscopy the immunoreactivity of epidermal proteins in normal and ultraviolet light (UVB) induced hyperplasia and malignant transformation. Reactivity to the antibody was seen over the entire epidermis of nontreated skin and hypertrophied epidermis which occurred at 6-8 weeks after initiation of UVB irradiation. However, the reactivity diminished when malignant changes took place in the epidermal cells. Almost complete disappearance of the immunoresponse was observed in squamous cell carcinoma produced by further UVB radiation. These results suggest that the reactivity of this urea extractable protein serves as an additional immunologic marker for normal epidermal cells. Alterations in the immunoreactivity parallels UVB induced carcinogenesis.

Animals↗
PubMed2006

Inhibition of inflammatory nitric oxide production and epidermis damages by Saccharomycopsis Ferment Filtrate.

BACKGROUND: Yeast extracts have been shown to perform anti-inflammatory and cytoprotective activities. However, the effects of yeast extracts on lipopolysaccharide (LPS)-induced nitric oxide (NO) production and epidermal damages are still unclear. OBJECTIVE: To investigate the effect of Saccharomycopsis Ferment Filtrate (SFF) on LPS-induced NO production in RAW264.7 macrophages and epidermal damages. METHOD: RAW264.7 cells are incubated with LPS (25 ng/mL) and different concentrations of SFF. The amount of NO production is detected by Griess reaction. Additionally, the expression of inducible nitric oxide synthase (iNOS) and heme oxygenase-1 (HO-1) are detected by Western blotting. Artificial epidermis is also used to mimic the in vivo condition to investigate the protective effects of SFF on LPS- or ultraviolet radiation (UVR)-induced damages by histology and electron microscopy. RESULTS: The results show that SFF addition inhibits LPS-induced NO production and iNOS protein expression in a concentration-dependent manner without notable cytotoxicity in RAW264.7 cells, and induction of HO-1 protein expression by SFF was observed. Interestingly, both HO-1 inducers, hemin and CoCl2, significantly attenuated LPS-induced NO production and iNOS protein expression. The addition of CoCl2 potentiated the inhibitory effect of SFF on LPS-induced NO production. It seems that HO-1 protein participates in SFF inhibition of LPS-induced NO production. Furthermore, SFF exhibits significant protective effect on LPS- or UVR-induced damages in the artificial epidermis via histological and electron microscopic observations. CONCLUSION: This study provided the first evidence to indicate the beneficial effects of SFF in preventing NO production in macrophages and damages in epidermis, respectively. It suggests that SFF possesses potential to be further developed.

Animals↗
PubMed1985

Photochemotherapy in cutaneous T cell lymphoma and parapsoriasis en plaques. Long-term follow-up in forty-three patients.

Forty-three patients with clinical plaque- and tumor-stage mycosis fungoides, the erythrodermic/Sézary syndrome variant of mycosis fungoides, and parapsoriasis en plaques were treated with oral psoralens and ultraviolet A (PUVA). Pretreatment skin biopsies, evaluated by light microscopy, revealed seventeen diagnostic, seventeen suggestive, and nine nonspecific specimens. Clinical and histologic parameters were followed for an average of 38.4 months (range, 4-67 months). Twenty-five patients had complete clearing, and fourteen did not respond. Most patients in the complete-response group had either plaque lesions of mycosis fungoides or parapsoriasis en plaques prior to PUVA. Most patients in the no-response group had either tumor lesions or the erythrodermic/Sézary mycosis fungoides at the start of PUVA. In the no-response group the treatment modalities used prior to PUVA were twice the number used in the complete-response group. Patients in the complete-response group had clearing of their lesions after an average PUVA dose of 117 joules/cm2. Relapse occurred in seventeen patients after an average remission time of 6.3 months and responded to additional PUVA. Patients whose skin remained clear after the first course of PUVA continued to have clear skin for up to 58 months, with an average complete remission of 29.5 months by the end of the study period. Histologic evaluation before PUVA and at clearing revealed a definite trend toward a normal microscopic picture, but at least a mild inflammatory infiltrate usually persisted. At the end of the study period, the lesions of ten patients had entirely cleared for an average of 44 months, the lesions of five had cleared during a second course of PUVA, five had stable limited-plaque disease while receiving maintenance PUVA, eleven were undergoing electron beam radiation therapy or chemotherapy for progressive disease, ten had died, and two patients were lost to follow-up. Therefore, in the early stage of mycosis fungoides, PUVA may induce significant disease-free intervals. Prior treatment with a variety of modalities, the patient's age, and/or the duration of disease may affect response to PUVA.

Adult↗