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PubMed1967

Postirradiation cell division in 5-fluorouracil-pre-treated Escherichia coli.

The correlation between 5-fluorouracil-induced resistance to ultraviolet (UV) light and the ability of bacterial cells to repair irradiation damage was investigated in various strains of Escherichia coli. Preincubation with 5-fluorouracil did not influence the dark-repair mechanism. It affected, however, the UV light-induced damage of cell division in filament-forming strains. It is suggested that the delay in postirradiation macromolecular synthesis of 5-fluorouracil-pretreated bacteria plays a decisive role in the recovery process leading to cross cell wall-forming ability in the damaged strains.

Cell Division↗
PubMed2001

New applications for an old lignified element staining reagent.

The use is reported of Mirande's reagent in epifluorescence microscopy which permits a clear distinction between cellulosic and lignified tissues. Homogeneous Prespermatophytae and gymnosperm xylem appeared entirely green with Mirande's reagent under ultraviolet excitation, whereas heteroxyled angiosperm wood showed a mixed pink and blue-green colour. This coloration was due to the fluorescence of cellulose, since certain elements in dicotyledonous wood (parenchyma, fibres, xylem rays) are not entirely lignified. Monocotyledonous (Poaceae) lignin showed an intense blue fluorescence due to hydroxycinnamic acids bound to the cell wall. The method showed that lignification occurs first in the middle lamella, and later in the secondary wall of xylem cells. In addition, this staining technique proved useful in the study of lignin and suberin deposition in response to various stress factors.

Cellulose↗
PubMed2005

Hydrogen bonding effects on the surface structure and photoelectrochemical properties of nanostructured SnO2 electrodes modified with porphyrin and fullerene composites.

Hydrogen bonding effects on surface structure, photophysical properties, and photoelectrochemistry have been examined in a mixed film of porphyrin and fullerene composites with and without hydrogen bonding on indium tin oxide and nanostructured SnO2 electrodes. The nanostructured SnO2 electrodes modified with the mixed films of porphyrin and fullerene composites with hydrogen bonding exhibited efficient photocurrent generation compared to the reference systems without hydrogen bonding. Atomic force microscopy, infrared reflection absorption, and ultraviolet-visible absorption spectroscopies and time-resolved fluorescence lifetime and transient absorption spectroscopic measurements disclosed the relationship between the surface structure and photophysical and photoelectrochemical properties relating to the formation of hydrogen bonding between the porphyrins and/or the C60 moieties in the films on the electrode surface. These results show that hydrogen bonding is a highly promising methodology for the fabrication of donor and acceptor composites on nanostructured semiconducting electrodes, which exhibit high photoelectrochemical properties.

Electrochemistry↗
PubMed2005

Two-photon fluorescence imaging and reactive oxygen species detection within the epidermis.

Two-photon fluorescence microscopy is used to detect ultraviolet-induced reactive oxygen species (ROS) in the epidermis and the dermis of ex vivo human skin and skin equivalents. Skin is incubated with the nonfluorescent ROS probe dihydrorhodamine, which reacts with ROS such as singlet oxygen and hydrogen peroxide to form fluorescent rhodamine-123. Unlike confocal microscopic methods, two-photon excitation provides depth penetration through the epidermis and dermis with little photodamage to the sample. This method also provides submicron spatial resolution such that subcellular areas that generate ROS can be detected. In addition, comparative studies can be made to determine the effect of applied agents (drugs, therapeutics) upon ROS levels at any layer or cellular region within the skin.

Epidermis↗
PubMed1980

Identification of genetic elements associated with muscle structure in the nematode Caenorhabditis elegans.

A search for new mutants with altered body-wall muscle cell structure has been undertaken in the nematode C elegans. One-hundred seventeen mutants were isolated after mutagenesis with ethyl methanesulfonate or ultraviolet light, enrichment by a motility-requiring test, and screening by polarized light microscopy; 102 of these mutants were in ten previously established genes, whereas 15 mutants permitted the identification of seven new complementation groups in C elegans. Two of the new genes map on linkage group I (unc-94 and unc-95) and four genes are sex linked (unc-96, unc-97, unc-98, and unc-99). One complementation group (unc-100) could not be mapped because of the special characteristics of its cohort mutants. Representative mutants of the mapped genes were examined by polarized light and electron microscopy. All of the mutants exhibit disruptions of the normal A and I band organization of thick and thin filaments. Several of the mutants produce collections of thin filament-like structures. In one of these cases, HE177 demonstrated collections of somewhat wider, intermediate-sized filaments as well, and the HE195 mutant produces paracrystalline aggregates of thin filaments amidst looser arrangements of similar structures. The mutants in newly identified genes, as well as the new mutants in previously established genetic loci, have promise as tools in the study of myofibrillar assembly and function. Among the 22 complementation groups associated with body-wall structure in C elegans, it is likely that some genes code for regulatory and morphogenetic functions in addition to the well-studied structural, contractile, and calcium-associated proteins in muscle.

Animals↗
PubMed2005

Effects of ethyl and benzyl groups on the miscibility and properties of castor oil-based polyurethane/starch derivative semi-interpenetrating polymer networks.

Cornstarch derivative (ES), prepared using diethyl sulfate as an etherifying reagent, was blended with castor oil-based polyurethane (PU) prepolymer to obtain a series of semi-interpenetrating polymer network (semi-IPN) materials, named as UES films. Simultaneously, other kinds of semi-IPN (UBS2) were prepared from PU and benzyl starch (BS2) to compare the effects of the substitute groups. The differences in the miscibility and properties of the two series of materials were investigated using attenuated total reflection Fourier transform infrared spectroscopy, atomic force microscopy, dynamic mechanical thermal analysis, ultraviolet-visible spectroscopy, water-sensitivity and tensile testing. The experimental results revealed that UBS2 films exhibit stronger interfacial attraction and better phase mixing than the UES films, as a result of specific interactions between the PU hard segments and BS2 phenyl groups. The optical transmittance, water-resistivity, tensile strength, and elongation at break of the UBS2 films were clearly higher than those of the UES films containing the same concentration of PU. In particular, the miscibility and properties of the UES film with 40 wt.-% ES, were very poor, whereas the semi-IPN films containing 70 wt.-% benzyl starch still had a certain miscibility and good properties. Therefore, the phenyl groups play an important role in the improvement of the miscibility and properties of the semi-IPN materials.

Benzyl Compounds↗
PubMed1985

Effect of ultraviolet radiation on guinea pig epidermal Langerhans cell cytomembrane: light and electron microscopic studies.

The epidermal Langerhans cells (ELC) are thought to be the outermost station of the immune system. Their location in the suprabasal layer of the epidermis makes them susceptible to a continuous exposure to ultraviolet irradiation (UVR) and if UVR alters the ELC, this may in turn induce both local and systemic effects. In this paper we have shown that UVA and UVB exposure produced dose-dependent changes of ELC, characterized by disturbance of spatial distribution and aggregation of the ATPase loci located in the ELC cytomembrane after low-dose exposure (1-3 MED), and actual cytomembrane damage after high doses (4-6 MED). UVC exposure, on the other hand, produced effects that were different from those of both UVA and UVB: high UVC doses, in fact, even though able to induce ELC morphological changes, failed to significantly reduce their number. These findings provide ultrastructural evidence of the deleterious effects produced by UVR on ELC.

Adenosine Triphosphatases↗
PubMed1983

Dense particles and slow sedimenting particles produced by ultraviolet irradiation of poliovirus.

Low doses of u.v. radiation rapidly inactivate poliovirus, and the virus is progressively converted into dense particles (DPs) of buoyant density 1.44 g/ml in CsCl. The DPs are structurally and antigenically related to standard virus (N-antigen), i.e. they are indistinguishable from virus in their RNA and protein content and in their sedimentation properties. Furthermore, there is no difference in reactivity of the structural proteins of virus and DPs with the monofunctional reagent [3H]N-succinimidyl propionate (3H-NSP). However, DPs differ from virus in that their capsids are permeable to several ions, and they can be degraded by RNase and protease. Increasing the radiation dose causes a successive transformation of DPs into 105S slow-sedimenting particles (SSPs). The SSPs are antigenically related to 76S artificial empty capsids (AECs) or H-antigen, but they differ physically and structurally from them. The SSPs have a higher S value than AECs and contain all the capsid proteins, including VP4, and the RNA, both of these macromolecules being absent from AECs. It is concluded, therefore, that transformation from N- to H-antigenicity by u.v. radiation does not require release of RNA and VP4. Conversion of virus particles to SSPs correlates with altered reactivity of VP2 and to a lesser extent VP1 and VP3, with the monofunctional reagent 3H-NSP.

Centrifugation, Density Gradient↗
PubMed1982

Reversible cryogenic alteration of the ultraviolet absorption spectra of the olefinic bonds in lipid membranes.

In earlier studies it was found that the association of basic polypeptides with lipid vesicles drastically altered ultraviolet absorption by the olefinic bonds of the lipid. Such an effect suggested that the polypeptide was increasing the polarity of the chromophore environment by either direct interaction with the acyl chains or by inducing their hydration. It is reported here that freeze-thaw cycling, which was expected to allow hydration of the olefinic-bond region of the membranes, caused the same spectral alteration as vesicle interaction with basic polypeptides. When these vesicles were subsequently placed under conditions that would be expected to accelerate the escape of water entrapped within the membranes (i.e., by placing them under vacuum or adding sucrose to establish a high osmotic gradient to their exterior), the absorption spectrum was rapidly restored to that for olefinic bonds in a nonpolar environment. Since placing the polylysine- dioleoylphosphatidylcholine (DOPC) vesicle interaction product under the same conditions restored the spectral intensity, at 190 nm, to between 80 and 85% of that for the lipid in a nonpolar environment, it seems that a major effect of polylysine on DOPC membranes may be though induction of hydration of their interior.

Alkenes↗
PubMed2006

Ultraviolet irradiation-induced apoptosis does not trigger nuclear fragmentation but translocation of chromatin from nucleus into cytoplasm in the microglial cell-line, BV-2.

Chromatin condensation, decrease of nuclear volume, and nuclear fragmentation are key features of apoptosis (programmed cell death) in many eukaryotic cells. How chromatin is redistributed in a continuously shrinking nucleus is an intriguing question. To evaluate this interesting spatial problem, we studied the ultrastructural distribution of chromatin in distinct stages of apoptosis using the microglial cell-line, BV-2, as a model and UV irradiation as a trigger of apoptosis. During apoptosis, condensed chromatin accumulated initially at the nuclear periphery and, subsequently, occupied almost the entire nucleus. Surprisingly, nuclei did not fragmentize, but apoptotic cells showed condensed chromatin in the nucleus as well as in the nucleus-attached cytoplasm. During apoptosis, the nuclear envelope dilated and decreased in extension by formation of numerous electron lucent vesicles, which accumulated in the cytoplasm. Furthermore, we observed in BV-2 cells well-known apoptotic features, like increased caspase-3/7 activity and annexin V labeling, as well as a sequence of cell morphological alterations, including cell shrinkage, zeiosis, and formation of apoptotic bodies. Thus, our findings suggest that UV-induced chromatin degradation is not restricted to the nucleus but may also take place in the cytoplasm in BV-2 cells.

Animals↗
PubMed1989

Influence of far-ultraviolet radiation on the permeability of the outer membrane of Escherichia coli.

Far-ultraviolet radiation (254 nm) at a dose of 10, 20, and 30 J/m2 was found to disrupt the outer membrane permeability barrier of Escherichia coli to various antibiotics, dyes, and detergents. The degree of sensitization to these agents was proportional to the radiation dose. The irradiated cells showed a significant increase in the sensitivity of hydrophilic antibiotics (ampicillin, carbenicillin, penicillin), whereas much less sensitization was found towards hydrophobic probes (kanamycin, erythromycin, rifamycin SV, crystal violet, phenol, novobiocin) and detergents (dodecyl sulfate, bile salt, Triton X-100). The biochemical data and ultrastructural analysis of the outer membrane by freeze-etching have shown that the increase in phospholipid:protein ratio after irradiation had changed the architecture of the outer membrane from a highly asymmetric bilayer structure with densely packed lipopolysaccharide--protein particles on the outer half, to one predominantly exhibiting smooth phospholipid bilayer characteristics. The structure, composition, and barrier function of the outer membrane were restored to normal within 3 h of postirradiation incubation in nonproliferative medium. During this period, the acquisition of resistance towards a hydrophilic antibiotic (ampicillin) was faster than that for a hydrophobic agent (phenol).

Anti-Bacterial Agents↗
PubMed2004

SAMs of shape-persistent macrocycles: structure and binding on HOPG and Au(111).

Self-assembled monolayers of shape-persistent macrocycles have been adsorbed on highly oriented pyrolytic graphite and Au(111) substrates. Their structure and binding characteristics have been investigated by scanning tunneling microscopy, X-ray photoelectron spectroscopy, and ultraviolet photoelectron spectroscopy experiments. Special functionalization of the macrocycles for the first time has enabled their self-assembling and binding on a metal substrate and opened a new route for new functional nanostructures.

Gold↗
PubMed1983

[Electron microscopic study of the surface of nonirradiated and UV-irradiated human blood lymphocytes].

The action of the short-wave ultraviolet radiation (UV, 254 nm) upon the outer perimembrane layers (OPML) of the human blood lymphocytes was studied with the aid of electron microscopy. The alcian blue and ruthenium red dye was used for the contrasting of the OPML. The UV-exposure of cells in shown to lead to the diminution of the dye-adsorbing cell surface as well as to the change of the nature of the observed OPML structures. The problem of the connection between the structural changes of the cell surface with modification of antigen properties of immunocompetent cells is discussed.

Cell Membrane↗
PubMed1998

Apoptotic cell clearance in systemic lupus erythematosus. II. Role of beta2-glycoprotein I.

OBJECTIVE: To analyze the contribution of beta2-glycoprotein I (beta2-GPI) to apoptotic cell recognition by antiphospholipid antibodies (aPL) and macrophages from patients with autoimmune disease. METHODS: Phosphatidylserine expression by Jurkat cells undergoing apoptosis upon CD95 crosslinking or ultraviolet irradiation was verified by confocal microscopy of cells stained with fluorescein isothiocyanate-labeled annexin V. Beta2-GPI was purified by heparin/cationic-exchange chromatography and was biotinylated or used to purify beta2-GPI-specific antibodies by affinity chromatography. Binding to apoptotic cells was assessed by flow cytometry. The clearance of 3H-labeled, apoptotic cells by macrophages was assessed by beta counting. RESULTS: The array of epitopes generated by beta2-GPI association with apoptotic cells specifically targets their recognition and is required for their opsonization by human aPL. Nevertheless, beta2-GPI is not required for apoptotic cell clearance by human macrophages in the absence of aPL. CONCLUSION: The proinflammatory clearance of aPL-opsonized apoptotic cells, but not the nonphlogistic clearance of apoptotic cells by scavenger macrophages, depends on beta2-GPI.

Antibodies, Antiphospholipid↗
PubMed2003

Structural stability of adenovirus type 5.

Thermally induced structural changes in adenovirus type 5 (Ad) in the presence of either 2 or 10% sucrose were investigated using a variety of biophysical techniques. In solutions containing 2% sucrose, a highly cooperative transition in the structure of the virus was observed at 45 degrees C as detected by tryptophan fluorescence, derivative UV absorption spectroscopy, circular dichroism (CD), and dynamic and static light scattering. This transition resulted in (at least partial) disassembly of the virus and a concomitant increase in the accessibility of the viral DNA to the fluorescent dye, TOTO-1. Capsid disassembly was verified by transmission electron microscopy, which showed ruptured icosahedral vertices near 45 degrees C followed by complete capsid disassembly at higher temperatures. SDS-PAGE of thermally treated Ad suggests that the penton base (protein III) and protein IIIa (located in the peripentonal region) are significantly more labile than other capsid proteins and may be the initial instigators in capsid disassembly. Additional discrete structural transitions were observed in viral proteins using the aforementioned spectroscopic techniques. Thermally induced rearrangements of the condensed DNA at higher temperatures were also detected by the appearance of "psi"-like features in the CD spectra as well as a dramatic decrease in accessibility of DNA to TOTO-1. These transitions corresponded to discrete endothermic events that are also detected by differential scanning calorimetry. By increasing the concentration of sucrose to 10%, secondary and tertiary structural features of adenoviral proteins were significantly stabilized, although loss of quaternary structure at 45 degrees C was still observed.

Adenoviridae↗