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At least 469 records · Page 26Linked to original sources
PubMed1994

A new visible light DNA fluorochrome for confocal microscopy.

We have developed a new DNA-specific fluorochrome that is excited by visible light. This chemically uncharacterized fluorochrome readily penetrates tissue in whole mounts, gives a strong signal, is inexpensive to make and very easy to use. This preparation has several advantages over existing DNA fluorochromes in confocal laser microscopy applications. Many DNA fluorochromes are excitable by ultraviolet light. These have limited utility in confocal microscopy, where commonly used lasers produce only visible wavelengths of light. Other DNA fluorochromes are available that are excitable by visible light, but some have difficulty penetrating all cell types, while others have high background or fade quickly. This new fluorochrome overcomes these problems and has an emission spectra that makes it compatible with either rhodamine or Texas Red labeled reagents for double-label experiments. The ability to label all nuclei in a tissue and make three-dimensional reconstructions by confocal microscopy is extremely useful in examining cellular distributions within specific tissues.

Animals↗
PubMed2001

Effect of ultraviolet radiation on melanogenesis in four different types of cultured bovine ocular pigmented cells.

BACKGROUND: Ultraviolet radiation is thought to play a causative role in various ocular diseases such as macular degeneration, cataract, and possibly melanomas. Since most of the energy is absorbed by pigmented cells, the aim of this study was to examine and compare the reactions of different ocular melanocytic cells to ultraviolet light in vitro. MATERIALS AND METHODS: Bovine iris melanocytes, choroidal melanocytes, iris pigment epithelial cells, and retinal pigment epithelial cells were isolated and cultured. Semiconfluent cultures were exposed to ultraviolet radiation (280-380 nm). Cell number and melanin content were measured 10 days after radiation. Selected samples were examined by transmission electron microscopy. RESULTS: Following irradiation with ultraviolet light for 30 s, 60 s, and 120 s, the number of cells in culture decreased markedly. In contrast, total melanin content in the cultures of iris melanocytes, choroidal melanocytes, and iris pigment epithelial cells did not decrease despite the reduced number of cells. This finding suggested an increase in melanin per cell. However, the increase in average melanin content observed was not due to melanogenesis, because treatment with the melanogenesis inhibitor alpha-methyl-p-tyrosine did not reduce the melanin content of the cultures and electron-microscopic examination showed no morphological evidence of increased melanogenesis. CONCLUSION: In vitro, there was no convincing evidence of ultraviolet radiation-induced melanogenesis in ocular pigmented cells. Thus, it seems that ultraviolet radiation is a selection factor: more densely pigmented cells survive the treatment better than less pigmented cells.

Animals↗
PubMed1990

[The function of the posterior corneal epithelium after exposure to ultraviolet laser radiation].

The method of contact mirror microscopy was used for assessment of the state of posterior epithelium of rabbit corneas before and after the action of laser ultraviolet radiation, lambda = 0.337 mmc. It was found that the usage of energy density of 5-20 mwt/cm2 and time exposures [correction of expositions] of 1, 5, 10, 15 min. in the terms of follow-up from 1 hour to 3 months is harmless for cells of posterior epithelium of the cornea in experiment. The method of mirror microscopy widens criteria of in vivo objective assessment of coherent radiation action on the cornea, that is important for deciding the questions about security and optimization of energetic parameters of laser therapeutic actions.

Animals↗
PubMed1990

Acute effects of ultraviolet-B irradiation on the corneal surface of the pigmented rabbit studied by quantitative scanning electron microscopy.

The eyes of female pigmented rabbits were exposed to a single dose of UV-B (300 +/- 9 nm, 0.05 J/cm2 total dose) between 13.30 and 15.00 h. The average irradiance was 225 +/- 36 microW/cm2 delivered over 191 to 264 s. At various time periods thereafter (24, 48, 72 and 96 h post-irradiation), the animals were euthanized by pentobarbital overdose and the eyes fixed with 2% glutaraldehyde in 80 mM cacodylate buffer (pH 7.4, total osmolarity of 330-340 mOsm/L). Corneal quadrants were examined by high resolution scanning electron microscopy at 100 X and 500 X at-stage magnification at central, mid-peripheral and peripheral sites. The micrographs from the central cornea were subjected to a quantitative analysis using a computer based digitization system. A peak effect was observed at 48 h at which cellular exfoliation was noted at the corneal apex. In the region immediately adjacent to the exfoliating cells, the number of light and dark electron reflex cells decreased to 48 h while the numbers of medium-reflex cells decreased after 48 h. The relative surface area of all cells was also decreased at 48 h compared to unirradiated controls. Significant recovery was observed by 96 h. Mid-peripheral and peripheral sites were largely unaffected by this just supra-threshold irradiation.

Animals↗