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At least 865 records · Page 48Linked to original sources
PubMed2005

Pityriasis versicolor alba.

Pityriasis versicolor alba is a hypopigmented or depigmented variant of pityriasis versicolor characterized by maculous, partly pityriasiform, scaly depigmented lesions occurring particularly in seborrhoeic areas. Long-persisting hypopigmentation after healing of the pityriasis versicolor was first described by Gudden in 1853. Hypopigmentation and depigmentation were later differentiated as an independent variant of the disease. In 1848, Eichstedt recognized the pathogen-related character of pityriasis versicolor in its hyperpigmented form. Today it is generally accepted that the disease is caused by yeasts of the genus Malassezia, of which nine species are differentiated. It is controversial whether a single species is responsible for the disease. The pathogenesis of depigmentation has not been established. A screening effect by the scale layer as well as toxic effects on pigment synthesis by fungal metabolites have been discussed. With regard to the second mechanism, the newly discovered tryptophan-derived metabolites of M. furfur might be significant. Evidence-based data concerning the therapy of pityriasis versicolor alba do not exist. According to current recommendations, pityriasis versicolor should be rapidly treated with antimycotics, followed by ultraviolet therapy to induce maturation of existent melanosomes and accelerate repigmentation. However, depigmented lesions are difficult to improve by ultraviolet therapy.

Antifungal Agents↗
PubMed2006

[Study of DNA damage induced by potassium dichromate and glutathione with atomic force microscope].

OBJECTIVE: To observe calf thymus DNA damage induced by potassium dichromate in combination with glutathione (GSH). METHODS: Atomic force microscope and ultraviolet spectrum (UV) were used to observe the alterations of the DNA ultrastructure and absorption spectrum. RESULTS: Atomic force microscopy revealed no breaks of the DNA strand in response to treatment with potassium dichromate alone, but when coupled with GSH at proper concentrations, potassium dichromate induced alterations in the DNA structure and DNA fragmentation. UV examination also confirmed these findings by showing increased absorption intensity of the maximum UV peak following combined treatment of the DNA with potassium dichromate and GSH. CONCLUSION: These morphological and spectrographic evidences verified the important role of GSH in mediating the generation of various tumor-inducing intermediate products of potassium dichromate.

Animals↗
PubMed2005

Degradation of dyestuff wastewater using visible light in the presence of a novel nano TiO2 catalyst doped with upconversion luminescence agent.

A new upconversion luminescence agent, 40CdF2 x 60BaF2 x 0.8Er2O3, was synthesized and its fluorescent spectra were determined. This upconversion luminescence agent can emit five upconversion fluorescent peaks shown in the fluorescent spectra whose wavelengths are all below 387 nm under the excitation of 488 nm visible light. This upconversion luminescence agent was mixed into nano rutile TiO2 powder by ultrasonic and boiling dispersion and the novel doped nano TiO2 photocatalyst utilizing visible light was firstly prepared. The doped TiO2 powder was charactered by XRD and TEM and its photocatalytic activity was tested through the photocatalytic degradation of methyl orange as a model compound under the visible light irradiation emitted by six three basic color lamps. In order to compare the photocatalytic activities, the same experiment was carried out for undoped TiO2 powder. The degradation ratio of methyl orange in the presence of doped nano TiO2 powder reached 32.5% under visible light irradiation at 20 h which was obviously higher than the corresponding 1.64% in the presence of undoped nano TiO2 powder, which indicate the upconversion luminescence agent prepared as dopant can effectively turn visible lights to ultraviolet lights that are absorbed by nano TiO2 particles to produce the electron-cavity pairs. All the results show that the nano rutile TiO2 powder doped with upconversion luminescence agent is a promising photocatalyst using sunlight for treating the industry dye wastewater in great force.

Azo Compounds↗
PubMedDate not supplied

[Effect of gamma-radiation on ultraviolet fluorescence of rat lymphocytes].

Changes in the level of the proper UV-fluorescence ( UVF ) of rat blood lymphocytes are considered as a function of radiation dose and time after gamma-irradiation of animals. 24 h following irradiation with a dose of 0.5 Gy the UVF intensity decreased; with doses of 1-8 Gy, the level of cytofluorescence exceeded the control values. The effect of fluorescence at this time was not related to changes in a cell diameter whereas at later times following irradiation part of the effect was related to the growth of cell dimensions.

Animals↗
PubMed2001

Characterization of UV-irradiated dense/porous collagen membranes: morphology, enzymatic degradation, and mechanical properties.

Collagen-based membranous materials of various shapes (gel, film, sponge) are known to be the most promising materials in terms of facilitating the regeneration of dermal defects. In this study, dense and porous collagen membranes were fabricated using air-drying and freeze-drying processes, respectively, and the effect of ultraviolet (UV) radiation on the degree of membrane crosslinking was evaluated by in vitro biodegradation and mechanical testing. A non-irradiated membrane group was used as the negative control and a glutaraldehyde (GA) treated group as the positive control. Scanning electron microscopy showed that, as the freezing temperature decreased to -196 degrees C, the resultant mean pore sizes also decreased; optimal pore size was obtained at a freezing temperature of -70 degrees C. In vitro biodegradation and mechanical testing demonstrated that GA treatment or 4 hours of exposure to UV radiation significantly increased both resistance to collagenase and mechanical strength versus the untreated controls, regardless of the collagen membrane type (dense or porous). Our results suggest that UV treatment is a useful tool for the fabrication of collagen membranes designed to be used as dermal dressings.

Animals↗
PubMed1999

Scanning electron microscopical studies on the tegument of adult worms of Schistosoma mansoni originating from ultraviolet-irradiated and non-irradiated cercariae.

The surface topography and ultrastructural changes of Schistosoma mansoni worms developed from ultraviolet-irradiated cercariae were compared with those from non-irradiated cercariae. The tegument of worms developed from irradiated cercariae showed a variety of changes including the occurrence of oedemata and most of the tubercles being torn at the tip and having lost their spines on the dorsal surface of some male worms. In females, parts of the tegument were devoid of spines and surface lesions were present. The range and extent of these changes differed not only among individual worms but also between different regions of individual worms resulting in generalized deformities in those worms originating from irradiated cercariae.

Animals↗
PubMed1983

The immediate action of long-wave ultraviolet radiation (UVA) on suprabasal melanocytes in human skin: a transmission electron microscopical study.

The immediate effects of long-wave ultraviolet irradiation (UVA) in non-erythemal doses on suprabasal melanocytes in normal skin of healthy caucasians with skin types II and III was investigated with the transmission electron microscopy (TEM) in order to detect possible morphological changes. In skin type III the melanocytes remained essentially unaltered, but in skin type II, multiple pinocytotic vesicles, large vacuoles, swelling, and partial to total dissolution of the inner membranes of the mitochondria and numerous small vesicles associated with an enlarged Golgi apparatus were observed after 3.6 to 14.5 J/cm2 of UVA irradiation. No IPD reaction was observed in any of the subjects with skin type II irradiated with UVA up to 20 J/cm2.

Adult↗
PubMed1995

Structure and function of melanocytes: microscopic morphology and cell biology of mouse melanocytes in the epidermis and hair follicle.

Melanocytes characterized by their tyrosinase activity, melanosomes and dendrites locate in the basal layer of epidermis and hair bulb in the skin of mice. Melanocytes differentiate from undifferentiated melanoblasts derived from embryonic neural crest. Melanocyte-stimulating hormone plays an important role in the regulation of the differentiation of mouse melanocytes in the epidermis and hair bulb by inducing tyrosinase activity, melanosome formation, transfer of melanosomes and increased dendritogenesis. The proliferative activity of differentiating epidermal melanocytes of newborn mice during the healing of skin wounds is regulated by semidominant genes, suggesting that the genes are involved in regulating the proliferative activity of epidermal melanocytes during differentiation. The morphology and differentiated functions of mouse melanocytes are shown to be influenced by environmental factors such as ultraviolet and ionizing radiations. From the results of serum-free culture of mouse epidermal melanoblasts, basic fibroblast growth factor is shown to stimulate the sustained proliferation of melanoblasts in the presence of dibutyryl adenosine 3',5'-cyclic monophosphate and keratinocytes. In contrast, melanocyte differentiation in serum-free culture is induced by melanocyte-stimulating hormone in the presence of keratinocytes. These results suggest that the structure and function of mouse melanocytes in the epidermis and hair bulb are controlled by both genetic factors and local tissue environment, such as hormones and growth factors.

Animals↗
PubMed1982

A circular dichroism study of sheath contraction in pyocin R1.

Pyocin R1, a bacteriocin of Pseudomonas aeruginosa, is a protein particle shaped like a bacteriophage tail composed of a contractile sheath, core, baseplate and tail fibers. Alkaline treatment with sodium carbonate caused sheath contraction without considerable disassembly of other components. Circular dichroism (CD) spectra of pyocin R1 before and after the treatment, and of isolated sheath, were measured in wavelength regions around 220 and 290 nm at neutral pH. The alkaline treatment caused a red shift of the minimum from 208 nm to 212 nm. A marked difference in the CD spectrum was found in the near-ultraviolet region. THe difference is considered to be mainly due to a CD spectra change of tryptophan residues in the sheath subunits.

Bacteriocins↗
PubMed1972

Physical studies of isolated eucaryotic nuclei.

The degree of chromatin condensation in isolated rat liver nuclei and chicken erythrocyte nuclei was studied by phase-contrast microscopy as a function of solvent pH, K(+) and Mg(++) concentrations Data were represented as "phase" maps, and standard solvent conditions selected that reproducibly yield granular, slightly granular, and homogeneous nuclei Nuclei in these various states were examined by ultraviolet absorption and circular dichroism (CD) spectroscopy, low-angle X-ray diffraction, electron microscopy, and binding capacity for ethidium bromide Homogeneous nuclei exhibited absorption and CD spectra resembling those of isolated nucleohistone. Suspensions of granular nuclei showed marked turbidity and absorption flattening, and a characteristic blue-shift of a crossover wavelength in the CD spectra. In all solvent conditions studied, except pH < 2 3, low-angle X-ray reflections characteristic of the native, presumably superhelical, nucleohistone were observed from pellets of intact nuclei. Threads (100-200 A diameter) were present in the condensed and dispersed phases of nuclei fixed under the standard solvent conditions, and examined in the electron microscope after thin sectioning and staining Nuclei at neutral pH, with different degrees of chromatin condensation, exhibited similar binding capacities for ethidium bromide. These data suggest a model that views chromatin condensation as a close packing of superhelical nucleohistone threads but still permits condensed chromatin to respond rapidly to alterations in solvent environment.

Animals↗
PubMed1984

Effect of non-mode-locked ultraviolet laser radiation (334 nm) on the retina.

The eyes of three rhesus monkeys (Macaca mulatta) were exposed to non-mode-locked ultraviolet (UV) radiation at 334 nm. The beam incident at the corneal plane had a diameter of approximately 2.0 mm and a maximum power of 45-50 mW. Each eye received nine exposures with exposure times ranging from 0.1 to 8.0 s. The animals were euthanized at various times following exposure so that the eyes were examined at approximately 1 h and 1, 2, 5, 7, and 14 d post-exposure. Histologic lesions were primarily seen involving photoreceptors, and were qualitatively similar regardless of duration of exposure; although quantitatively more damage was seen at sites exposed for 4.0 to 8.0 s. The results indicate that retinal sensitivity to UV laser light is a wavelength effect, rather than due to laser mode-locking which was present in an earlier study but absent in this study.

Animals↗