PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Microscopy, Ultraviolet”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1990

Disruption of keratin intermediate filaments by ultraviolet radiation in cultured human keratinocytes.

Fluorescence microscopy has been utilized to investigate the effects of UV irradiation on the organization of keratin intermediate filaments in normal human epidermal keratinocytes. Sun lamp irradiation induced the condensation of keratin intermediate filaments into the perinuclear region and inhibited the reorganization of keratin filaments normally induced by Ca2+. Exposure to UVC appeared to disrupt keratin filaments similarly, whereas UVA had no discernible effect.

Cells, Cultured↗
PubMed1996

Actin polymerization and depolymerization during apoptosis in HL-60 cells.

Little is known about the biochemical "machinery" responsible for the morphological features of apoptosis, although the cytoskeleton is presumed to be involved. Using flow cytometry, polyacrylamide gel electrophoresis, and fluorescence microscopy, we show that apoptosis induced by ultraviolet (UV) irradiation or 80 micrograms/ml etoposide correlates with early transient polymerization and later depolymerization of filamentous (F)-actin and dramatic changes in visible microfilament organization. Depolymerization of F-actin began before the formation of apoptotic bodies and was ultimately composed of decreases in both the detergent-insoluble (40%) and detergent-soluble (50%) pools of F-actin. Dihydrocytochalasin B (H2CB), which blocked apoptotic body formation, depolymerized F-actin in the detergent-insoluble pool only. Visually, H2CB treatment disrupted microfilament organization, resulting in short, brightly stained microfilaments dispersed throughout the cytoplasm. In contrast, apoptotic cells contained a network of fine microfilaments with bright staining concentrated at the site of apoptotic body formation. Together, these results suggest that reorganization of the microfilament network is necessary for the formation of apoptotic bodies and that depolymerization of F-actin may also be a necessary component of the process of apoptosis.

Actins↗
PubMed1987

Electron microscopic identification of supercoiled regions in complex DNA structures.

When intracellular lambda replicative intermediates (theta structures) are intercalated with psoralen and then irradiated with long wavelength ultraviolet light (u.v.), interstrand crosslinks are produced. After purification and denaturation of these theta structures, a global difference in denaturation can be observed by electron microscopy; parental sections are essentially native whereas daughter segments are highly denatured. This difference can be explained if parental sections are covalently continuous (and therefore able to supercoil) and daughter segments are not. Due to the higher thermal stability of supercoiled DNA, parental DNA will remain native while daughter sections will denature. Because these structures are crosslinked, the thermal treatment does not lead to dissociation of the highly denatured daughter strands. Experiments with simple negatively supercoiled plasmid circles support the above conclusions. When circles are crosslinked with psoralen-u.v. and then denatured, they remain native because of the higher thermal stability of covalently closed structures. If the circles are linearized before heating but after the psoralen-u.v. treatment, the thermal stability effect is eliminated and the molecules become highly denatured. In this case, however, the crosslinking density is found to be higher than in samples linearized before psoralen-u.v. treatment. This, therefore, shows that crosslinking density also reflects the superhelical state of the molecule at the time of psoralen-u.v. treatment. Two different properties can be used to discriminate between supercoiled and covalently discontinuous domains in complex DNA structures. First, supercoiled regions remain native while covalently discontinuous segments denature following a thermal treatment. This effect requires that covalent continuity exists up to and during the heating treatment. Second, because negative superhelicity enhances psoralen intercalation, crosslinking density is higher in these regions. Even if supercoiled domains are destroyed after the psoralen-u.v. treatment, the imprint of superhelicity is retained and can be recognized as a higher than normal crosslinking density.

Bacteriophage lambda↗
PubMed2000

Morphological observation on cell death and phagocytosis induced by ultraviolet irradiation in a cultured human lens epithelial cell line.

The purpose of this study is to observe dynamic morphological changes induced by ultraviolet (UV) irradiation in a cultured human lens epithelial cell line using electron microscopy, cell viability staining, time-lapsed videography and immunohistochemistry. Human lens epithelial cell line SRA 01-04 was cultured in Dulbecco's Modified Eagle Medium (DMEM) containing 20% fetal bovine serum. Subconfluent cells were irradiated under a bank of UV lamps, which emitted 275-400 nm radiation with a maximum at 310 nm. The UV intensity was 20 microW cm(-2)at dosages from 0 to 10 mJ cm(-2). Alterations in the morphology of the living cells were monitored and recorded with phase-contrast microscopy and time-lapsed videography. At different times, the cells were fixed and examined by transmission electron microscopy (TEM), diamidinophenolindole (DAPI) staining, and in situ immunohistochemistry using TdT-mediated dUTP-biotin nick end labeling (TUNEL). Cell viability was also assessed with crystal violet staining. At low doses of UV exposure (2-5 mJ cm(-2)), time-lapsed videography revealed definitive cell death that appeared to be primarily apoptotic. The dead cell debris was engulfed and phagocytosed by neighboring living cells. Phase-contrast microscopy and TEM demonstrated that, at UV 10 mJ cm(-2), the cells not only showed typical apoptosis such as nuclear membrane shrinkage, chromatin condensation, and fragmentation into apoptotic bodies, but also necrosis such as swelling of the nucleus and cell body, and disruption of the plasma membrane. In support, DNA staining and in situ immunohistochemical reactions in the UV irradiated cells were both positive. The phagocytotic process was also seen with TEM. UV irradiation thus appears to cause both apoptosis and necrosis in the cultured human lens epithelial cell line. Active migration and phagocytosis of the cells appear to be stimulated by UV-induced damage. These findings may also aid in the understanding of UV injury and repair mechanisms of lens epithelial cells in vivo.

Apoptosis↗
PubMed1996

Novel compliant and tissue-permeable microporous polyurethane vascular prosthesis fabricated using an excimer laser ablation technique.

A small-diameter vascular prosthesis with a multiply pored structure could have great potential to elevate the patency rate, for the following two reasons: 1) increased flexibility of the graft may increase compliance matching, consequently minimizing intimal hyperplasia; and 2) enhanced transmural tissue ingrowth may accelerate endothelialization. In this study, we fabricated a polyurethane (PU)-based artificial graft with well-controlled micropores in terms of their diameter and distribution, which was achieved using a computer-aided excimer laser (KrF) ablation technique. Three types of microporous PU tubes (2 mm in internal diameter, 100 microns in wall thickness) were designed: pore size (100 microns) and longitudinal pore-to-pore distance (200 microns) were constant, and circumferential pore-to-pore intervals were 60 degrees (type 1), 30 degrees (type 2), and 15 degrees (type 3). The fabricated prostheses were coated with photoreactive gelatin, which was photogelled and chemically fixed on PU surfaces upon ultraviolet light irradiation. Scanning electron microscopy showed that pore size and arrangement were precisely controlled as designed, and that a gelatinous hydrogel layer was formed over the entire luminal surface. The stiffness parameter (beta), inversely related to compliance, was determined from the change in external diameter against intraluminal pressure. An increase in the number of pores around the circumference decreased the beta value. The type 3 graft, the stiffness parameter of which was very close to that of human coronary artery, was the most compliant among the three types. The combination of excimer laser-directed microporing and photochemical surface processing techniques enabled the development of a novel compliant small-caliber vascular prosthesis, which is expected to show enhanced transmural tissue in growth in vivo.

Blood Vessel Prosthesis↗
PubMed1998

Microscopic analysis of NADH fluorescence during aerobic and anaerobic liver preservation conditions: A noninvasive technique for assessment of hepatic metabolism.

Gaseous insufflation of oxygen via the venous vascular system is thought to be an useful tool for preventing anoxic tissue injury during extended time periods of ischemic preservation and for allowing for an improved recovery of organ function after transplantation. The present study aimed at the application of a noninvasive technique for monitoring effectiveness and homogeneity of gaseous areation by using an epiillumination microscopic technique for assessment of tissue nicotinamide adenine dinucleotide (NADH) fluorescence. Rat livers were flushed with and stored in University of Wisconsin solution at 4 degrees C for 48 h (n = 20). In half of the experiments (n = 10) gaseous oxygen was applied subsequent to organ harvest. Using ultraviolet-excitation high-resolution microscopy and computer-assisted image analysis liver surfaces were scanned for NADH intensity and spatial heterogeneity at 1, 24, and 48 h preservation time. Livers simply stored without aeration served as controls (n = 10). NADH intensity data were compared with corresponding data of tissue adenosine triphosphate (ATP) concentrations determined enzymatically. NADH fluorescence already differed at 1 h preservation between the two groups with significantly lower values in the aerobically stored livers. NADH fluorescence further decreased between 1 and 24 h preservation and remained low until 48 h, whereas in the anaerobically stored livers NADH fluorescence was found to be constantly high over the entire observation period. Aerobic storage resulted in rather homogeneous tissue oxygenation with an intrahepatic variation of NADH fluorescence <20%. In parallel, oxygen persufflation appropriately restored tissue ATP content within 1 to 24 h of preservation, while the simply stored livers exhibited pronounced depletion of ATP. We demonstrate for the first time that by means of retrograde gaseous oxygenation, ischemic livers can be readily and effectively oxygenated. Our study further indicates that the noninvasive microscopic analysis of tissue NADH fluorescence may be an useful tool for estimating efficiency of strategies in organ preservation.

Adenosine↗
PubMed1999

Role of P-glycoprotein in human natural killer-like cell line-mediated cytotoxicity.

Natural killer (NK) cells express the highest amount of P-glycoprotein (Pgp), a product of the multidrug resistance (MDR) 1 gene, among lymphoid cells, and our previous studies demonstrated that Pgp is required for NK cell-mediated cytotoxicity. In this study we examined the role of Pgp in NK cell-mediated cytotoxicity using a human NK-like cell line, i.e., YTN cells and two MDR reversing agents, nicardipine and its structural analog, AHC-93. These two agents inhibited the Pgp function (rhodamine-123 excretion) as well as cell-mediated cytotoxicity, confirming that Pgp is critical for NK cell-mediated cytotoxicity. As revealed by video-rate ultraviolet laser-scanning confocal microscopy, AHC-93 did not inhibit the increase in the intracellular calcium concentration upon binding to target cells, whereas nicardipine did, as reported previously. These two reagents relocated acridine orange dye from lysosomes to the cytoplasm at concentrations similar to those required for the inhibition of cell-mediated cytotoxicity. These results suggest that Pgp is directly or indirectly involved in pH regulation in lysosomes, but not in calcium homeostasis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗