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At least 685 records · Page 38Linked to original sources
PubMed1998

Reduction in number and morphologic alterations of Langerhans cells after UVB radiation in vivo are accompanied by an influx of monocytoid cells into the epidermis.

Acute, low-dose ultraviolet B (UVB) radiation impairs contact hypersensitivity induction in mice by a mechanism due at least in part to Langerhans cells alterations. To better define the effects of UVB on Langerhans cells, we have compared the action of this agent on the skin of intact mice and in skin explants incubated in vitro up to 24 h. Using immunofluorescence, we detected a reduction in the length of the dendrites of Langerhans cells and a significant reduction in the number of Ia-positive Langerhans cells per unit area within 2 h of UVB; these changes reversed within 24 h in vivo, but not in vitro. By electron microscopy, the number of dendritic cells per 100 basal keratinocytes increased in vivo, but decreased in vitro by 2 h after UVB, a discordance that was significant. On the contrary, the number of dendrite profiles per dendritic cell body decreased significantly 2 h after UVB, both in vivo and in vitro. Many epidermal dendritic cells, 2 h after UVB in vivo, were deficient in cytoplasmic organelles, whereas the few cells that remained after UVB in vitro retained their Birbeck granules, and displayed many, dilated cytoplasmic vesicles. We interpret these data to mean that low doses of UVB radiation destroy the functional and morphologic integrity of epidermal Langerhans cells, and that these cells are rapidly replaced by precursor cells that mature in situ into normal-appearing Langerhans cells.

Animals↗
PubMed1974

Purification of naked intranuclear particles from human liver infected by hepatitis B virus.

The isolation and purification of the naked intranuclear particles of a human liver infected with hepatitis B virus is described. The particles had a diameter of 27-28 nm, were hexagonal, and showed the presence of capsomeres and spikes with lengths of 7-10 nm projecting from the surfaces. The particles formed cubic arrays with center-to-center distances of 40-42 nm. The overall particle symmetry was icosahedral. The ultraviolet absorption spectrum of the particles showed a peak at 264 nm with a shoulder at 280 nm. Endogenous DNA polymerase activity was not detected in fractions containing particles. DNA polymerase activity was present when activated DNA or d(A-T)(n) was used as exogenous template.

Absorption↗
PubMed1964

ISOLATION AND PRELIMINARY CHARACTERISTICS OF THREE BACTERIOPHAGES ASSOCIATED WITH A LYSOGENIC STRAIN OF PSEUDOMONAS AERUGINOSA.

Feary, Thomas W. (Tulane University School of Medicine, New Orleans, La.), Earl Fisher, Jr., and Thelma N. Fisher. Isolation and preliminary characteristics of three bacteriophages associated with a lysogenic strain of Pseudomonas aeruginosa. J. Bacteriol. 87:196-208. 1964.-Three bacteriophages designated 7v, 7m, and 7s were isolated from a lysogenic strain of Pseudomonas aeruginosa designated Ps-7. The three viruses were found to be completely unrelated on the basis of plaque morphology, host range, serology, ultraviolet induction, sensitivity to heat, and particle morphology as revealed by electron microscopy. In addition, it was shown that the three phages were incapable of plaque formation on bacteria other than various strains of P. aeruginosa. Of the three phages, only phage 7v was capable of plaque formation on strain Ps-7. The growth of phage 7v on strain Ps-7 exhibited properties which suggest that this virus arises as the result of mutation in a temperate phage for which strain Ps-7 is lysogenic. Phages 7m and 7s are incapable of plaque formation on strain Ps-7, but are adsorbed at characteristic rates to cell suspensions of strain Ps-7. The relationship between phage 7m and strain Ps-7 was shown to meet the classical criteria for lysogeny. Because phage 7s contains ribonucleic acid as its nucleic acid component, it was concluded that its production by strain Ps-7 and the demonstration of immunity of strain Ps-7 to infection by phage 7s were not sufficient evidence to define the nature of the relationship between phage 7s and P. aeruginosa strain Ps-7. It was observed that under certain conditions the infectious titer of phage 7s preparations are markedly reduced in the presence of ribonuclease.

Bacteriophages↗
PubMed1990

Ultraviolet-mediated antimycotic activity of alpha-terthienyl on Microsporum cookei.

Alpha-terthienyl (alpha-T) in the presence of UV-A irradiation reduced the growth rate of Microsporum cookei. In the dark, alpha-T accumulated in small diffuse vacuoles within the hyphae. After UV-A treatment, alpha-T caused damage to the membranes of the nucleus, mitochondria and endoplasmic reticulum. Plasmolytic and autolytic changes occurred resulting in plasma membrane breakage and cell wall aberrations. UV-A activated alpha-T would appear to target membrane proteins.

Microscopy, Electron↗
PubMed1988

Ultrastructural changes in epidermal Langerhans cells and melanocytes in response to ultraviolet irradiation, in Australians of Aboriginal and Celtic descent.

The effects of exposure to small doses of artificial ultraviolet radiation (UVR) on the ultrastructure of epidermal Langerhans cells (LC) and melanocytes were studied in two groups of Australian subjects, one of Aboriginal and the other of Celtic descent. UV exposure induced an apparent depletion of LC in the epidermis of both groups. However, LC depletion in the Aboriginal subjects was associated with apoptosis, whereas organelle and membrane disruption in the LC of Celtic subjects suggested a reduction by direct cellular damage. LC in Aboriginal epidermis tended to become relocated at more superficial levels following UV exposure, and their Birbeck granules became more numerous. LC in Celtic epidermis appeared to become relocated in a basal location and contained fewer Birbeck granules. The central lamina of the Birbeck granules in Aboriginal LC, which was more electron-dense than that in Celtic subjects prior to UV treatment, was temporarily lost following treatment, while the ultrastructure of Birbeck granules in Celtic LC was unchanged. LC and 'indeterminate cells' in intimate association with lymphocyte-like cells occurred in the basal layer of Celtic epidermis 5 days after exposure. These complexes were not observed in Aboriginal epidermis although isolated lymphocyte-like cells were observed in the same location. Melanocytes in Aboriginal epidermis contained greater numbers of melanosomes than those in Celtic epidermis throughout the experiment. Inactive epidermal melanocytes in Celtic subjects initially responded to UV exposure with a slight increase in melanosome content followed by a substantial further increase, whereas active melanocytes in the Aboriginal subjects showed the opposite response. The implications of the different responses of LC and melanocytes in the two groups, in relation to immunological function of the epidermis and the marked racial difference in the incidence of skin cancer, are discussed. Cancer of the skin, particularly basal and squamous cell carcinoma, occurs primarily in people with fair skin who burn easily following exposure to ultraviolet radiation (UVR). In contrast, the incidence of skin cancer in inherently dark-skinned people is low. Melanin is synthesized by melanocytes in response to UVR and is thought to protect epidermal cells against damage to their genetic material by absorbing UVR and thereby reducing its penetration into the skin. Thus darkly pigmented skin is more resistant to the effects of UVR.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1987

Disassembly of the mammalian metaphase chromosome into its subunits: studies with ultraviolet light and repair synthesis inhibitors.

Metaphase chromosomes of a simian virus-transformed Indian muntjac cell line have been examined by scanning electron microscopy of material in which the fully packed metaphase structure is progressively relaxed. Such chromosomes are seen in standard, spread preparations of ultraviolet light-irradiated, metaphase-arrested cells, which have been incubated in the presence of inhibitors of DNA synthesis; they are processed for electron microscopy by trypsinization, further fixation and osmium impregnation. Decondensation is initially associated with a gradual elongation and loosening of the chromosome axis and, as loosening proceeds, the appearance of unexpected higher order structures--clusters of 20-40 nm diameter fibres. The arrangement of the clusters shows much variation between spreads. In the most fully extended chromosomes clusters are arranged in two longitudinal series with pairing between sister chromatids; the diameter of the majority of clusters in such chromosomes is in the range 0.4-0.6 micron. In the final stages of decondensation, clusters separate and individual chromosomes are no longer recognizable. Similar fibre clusters are found in interphase nuclei prepared by the same method. We suggest that the clusters of chromatin fibres may assemble as intermediates in the construction of an axial structure, which is further compacted in the fully condensed metaphase chromosome.

Animals↗
PubMed2000

The ultraviolet action spectrum for stomatal opening in broad bean.

The ultraviolet action spectrum for stomatal opening was measured using epidermal peels from leaves of broad bean (Vicia faba). The spectrum was calculated from hyperbolic fluence response curves using 11 wavelengths ranging from 275 to 459 nm. The action spectrum exhibits a major peak at approximately 280 nm and a minor peak at approximately 360 nm. The response at 280 nm is about three times greater than the response at 459 nm. Under the conditions utilized (i.e. the absence of saturating red light), stomatal opening saturated at extremely low fluence rates: <0.2 micromol m(-2) s(-1) at 280 nm, and approximately 1.0 micromol m(-2) s(-1) at 459 nm. The threshold for blue-light-induced stomatal opening was approximately 0.02 micromol m(-2) s(-1). In light-mixing experiments, the addition of 280 nm light to saturating 650 nm (red) light caused additional stomatal opening, which is indicative of separate photoreceptors. In contrast, adding 280 nm of light to saturating 459 nm (blue) light did not increase stomatal opening, suggesting that they both excite the same receptor. The results with white light were similar to those with blue light. We infer that ultraviolet light acts via the blue light photoreceptor rather than through photosynthesis. The additional absorbance peak at 360 nm suggests that the chromophore is either a flavin or a cis-carotenoid, both of which exhibit peaks in this region. It is proposed that the chromophore can be excited either directly by blue light or by energy transferred from the protein portion of the protein-pigment complex after it absorbs 280 nm light.

Fabaceae↗
PubMed1960

[Electron microscopic study of the nuclear transformations 05 E. coli K12S and K12S (lambda 26) after irradiation with ultraviolet rays and x-rays].

Nuclear transformations induced in E. coli K12S and K12S(lambda(26)) by ultraviolet radiations and x-rays have been studied with ultrathin sections in the electron microscope. The nucleoplasm keeps its normal aspect during "fragmentation" and during "condensation" of the nucleus into the "vesicular" form. Serial sections show that the "fragmented" nucleus consists in reality of only one very tortuous vacuole. No difference either in the shape or in the fine structure of the nucleus could be observed between the lysogenic strain and the non-lysogenic strain. A high concentration of NaCl has a "condensation" effect on the fragmented nuclei and decreases the induction rate.

Cell Nucleus↗
PubMed2003

Investigation of normal and malignant laryngeal tissue by autofluorescence imaging technique.

OBJECTIVE: During oncogenesis significant changes in tissue properties occur that result in alteration of fluorescence characteristics of the tissue. The differences in autofluorescence between normal and malignant tissues offer new possibilities in detecting epithelial pathological lesions. AIM: The aim of our study was to determine the usefulness of autofluorescence technique in diagnostic of laryngeal tumors. MATERIAL AND METHODS: Fluorescence in larynxes from 10 laryngectomized cancer patients was induced by excitation light at 360-450 nm wavelength. As a light source, mercury lamp and laser (404 nm) were used. The CCD camera captured the fluorescent light emitted. Normal epithelium and cancer tissue were also analyzed on fluorescence microscopy. RESULTS: Laryngeal carcinoma tissues when excited with ultraviolet or blue light generate attenuated or absent autofluorescence in the green light band compare with normal epithelium where strong signal around 505 nm was detected. Average value of maximal autofluorescence intensities was 26.2V (range 18-35) and 4.4V (range 2-8) in healthy and cancerously changed mucosa respectively. Spectral analysis revealed that autofluorescence signal from unchanged mucosa (around 505 nm) was significantly higher compared to cancer tissue (P=0.005). CONCLUSIONS: It seems that autofluorescence imaging may be a supplementary tool in diagnosis of laryngeal tumors.

Adult↗
PubMed1995

Role of the centrosome in mitosis: UV micro-irradiation study.

Ultraviolet micro-irradiation (UV-MI) of the PK (pig kidney embryo) cell centrosome (lambda max = 280 nm, spot diameter 1.6 mm, exposure time 5-15 s) at metaphase and anaphase resulted in functional damage of the centrosome. After UV-MI of the centrosome at early metaphase, chromosomes quickly (in 1-3 min) moved away from the irradiated pole and then encircled the non-irradiated pole. Within 10 min after UV-MI the spindle disassembled and chromosomes remained unseparated. The minimal dose inducing this effect in 90% of cells was accumulated in 5 s. After the same UV-MI at late metaphase, chromosomes shifted towards the non-irradiated pole; however, anaphase started and chromosome motion towards the non-irradiated pole continued normally. UV-MI of the centrosome at early anaphase for 5-15 s slowed down and then stopped chromosome motion towards the irradiated pole. This was a result of rapid (within 2-3 min) disorganization of the half-spindle. Chromosomes continued to move towards the opposite pole normally, while cytokinesis was significantly retarded. No visible lesion was revealed by electron microscopy after 5 s UV-MI, while 15 s irradiation resulted in the truncation of the microtubule bundles 1.5-2 microns from the centrosome. We concluded that UV-MI inactivates the centrosome and induces disaggregation of microtubule initiation sites. The critical point (checkpoint) in mitosis up to which this damage induces mitotic arrest is mid-metaphase.

Anaphase↗
PubMed1987

The efficacy of a UV-blocking soft contact lens in protecting cornea against UV radiation.

Recently, it has been shown that UV keratitis is more serious than previously thought because it is not limited to the corneal epithelium but also involves the stroma and the endothelium. It is, therefore, very important to avoid ultraviolet radiation (UVR) damage, and the purpose of the present study was to examine the ability of a UV absorbing hydrogel lens to filter such wavelengths. Ultrastructural observations of rabbit corneas showed that a regular soft (Vistamarc normal) contact lens offered no protection, and since wearing one adds stress to the cornea it seems possible that the cornea may be more vulnerable to UVR trauma. A UV absorbing soft contact lens (Vistakon UV-BLOC) provided complete protection to all corneal layers. Subepithelial nerve fibres in the traumatized corneas were mostly of normal morphology and may explain why UV keratitis is a very painful experience. It was concluded that a UV absorbing soft contact lenses with acceptable clinical performance may be prescribed on a routine basis.

Animals↗
PubMed1986

Radiation of the fiberoptic illuminator of an operating microscope.

Relative radiation spectrum of a fiberoptic illuminator of an operating microscope (Zeiss Opmi 6) was measured with a spectrophotometer within the range of 350 to 1100 nm. Total irradiance at the corneal level was measured with a radiometer within the range of 250 to 4000 nm. Illumination was measured with a standard illuminometer. Two selective filters were used to optimally reduce the total radiation. A Schott filter GG 420 was used to cut off ultraviolet radiation and a Schott thermal filter KG 1 to reduce intrared radiation. Measured without filters the energy of radiation of wavelengths shorter than 400 nm was only 0.05% of the total energy of radiation, 78.5% was within the range of 400 to 780 nm, and 21.4% was produced by radiation of wavelengths longer than 780 nm. Corresponding values measured with selective filters were 0.003, 95.4 and 4.6. Irradiance at the corneal level was 7.7 mW/cm2 without filters and 3.8 mW/cm2 with selective filters, and the corresponding illumination levels were 21,300 and 16,500 lux. Using selective filters the total irradiance was effectively reduced causing only a minor reduction of the illumination level and a small just noticeable alteration of the colour of the operating field.

Cornea↗