Immunochemical detection of sequence-specific modifications to DNA induced by UV light

Sequence specificity of antibodies to UV-damaged DNA has not been described previously. The antisera investigated here were specific for UV-modified DNA and were absolutely dependent upon the presence of thymine residues. Using a series of oligonucleotides in competition ELISA, increased inhibition was observed with increasing chain length of UV-polythymidylate. A minimum of three adjacent thymines was required for effective inhibition; alone, dimers of thymine were poor antigens. Although UV-irradiated poly(dC) was not antigenic, cytosines could partially replace thymines within the smallest effective epitope (T-T-T) with a high degree of sequence specificity, not previously described. The main epitope induced by UV was formed from adjacent thymines and either a 3' or a 5' pyrimidine.

Conjunctival UV autofluorescence - prevalence and risk factors

Purpose: Autofluorescence of ultraviolet (UV) light has been shown to occur in localised areas of the bulbar conjunctiva, which map to active cellular changes due to UV and environmental exposure. This study examined the presence of conjunctival UV autofluorescence in eye care practitioners (ECPs) across Europe and the Middle East and its associated risk factors. Method: Images were captured of 307 ECPs right eyes in the Czech Republic, Germany, Greece, Kuwait, Netherlands, Sweden, Switzerland, United Arab Emirates and the United Kingdom using a Nikon D100 camera and dual flash units through UV filters. UV autofluorescence was outlined using ImageJ software and the nasal and temporal area quantified. Subjects were required to complete a questionnaire on their demographics and lifestyle including general exposure to UV and refractive correction. Results: Average age of the subjects was 38.5±12.2 years (range 19-68) and 39.7% were male. Sixty-two percent of eyes had some conjunctival damage as indicated by UV autofluorescence. The average area of damage was higher (p=0.005) nasally (2.95±4.52mm2) than temporally (2.19±4.17mm2). The area of UV damage was not related to age (r=0.03, p=0.674), gender (p=0.194), self-reported sun exposure lifestyle (p>0.05), geographical location (p=0174), sunglasses use (p>0.05) or UV-blocking contact lens use (p>0.05), although it was higher in those wearing contact lenses with minimal UV-blocking and no spectacles (p=0.015). The area of UV damage was also less nasally in those who wore contact lenses and spectacles compared to those with no refractive correction use (p=0.011 nasal; p=0.958 temporal). Conclusion: UV conjunctival damage is common even in Europe, Kuwait and UAE, and among ECPs. The area of damage appears to be linked with the use of refractive correction, with greater damage nasally than temporally which may be explained by the peripheral light focusing effect.

Oxygen free radicals denature human IgG and increase its reactivity with rheumatoid factor antibody

Rheumatoid inflammation is characterised by the production of rheumatoid factor antibodies directed against denatured IgG. Oxygen free radicals have the potential to denature all manner of proteins and can be generated by activated phagocytic cells in the inflamed joint. By modifying routine ELISA and nephelometric procedures for measuring rheumatoid factor, (i.e. substituting free radical altered IgG for rabbit and heat aggregated IgG as antigens) we have observed that oxygen radicals, generated by (1) UV light and (2) PMA-activated neutrophils, give rise to monomeric and polymeric forms of IgG which have increased reactivity towards IgM and IgA polyclonal rheumatoid factor antibodies. We conclude that free radical alteration of IgG may be a stimulus to the formation of immune complexes with rheumatoid factor antibody, thereby promoting and amplifying tissue damage during rheumatoid inflammation.

Synthesis and evaluation of novel polymer modifiers for biodegradable polymers

The effects of ester plasticizers and copolymers on the mechanical properties of the natural biodegradable polymers, poly(3-hydroxybutyrate) [PHB] and poly(lactic acid) [PLA] have been studied after subjecting to melt processing conditions. Ester plasticizers were synthesized from citric, tartaric and maleic acids using various alcohols. A variety of PLA copolymers have also been prepared from poly(ethylene glycol) derivatives using stannous octanoate catalysed ring opening polymerisations of DL-lactide. A novel PLA star copolymer was also prepared from an ethoxylated pentaerythritol. The structures of these copolymers were determined by NMR spectroscopy. The plasticizing effect of the synthesised additives at various concentrations was determined. While certain additives were capable of improving the mechanical properties of PLA, none were effective in PHB. Moreover, it was found that certain combinations of additives exhibited synergistic effects. Possible mechanisms are discussed. Biotic and abiotic degradation studies showed that the plasticizers (esters and copolymers) did not inhibit the biodegradability of PHB or PLA in compost at 60°C. Simple toxicity tests carried out on compost extract and its ability to support the growth of cress seeds was established. PLA was found to be susceptible to limited thermal degradation under melt processing conditions. Conventional phenolic antioxidants showed no significant effect on this process, suggesting that degradation was not predominantly a free radical process. PLA also underwent photo-oxidative degradation with UV light and the process could be accelerated in the presence of a photoactivator such as iron (III) diisononyl dithiocarbamate. The mechanisms for the above processes are discussed. Finally, selected compounds were prepared on a pilot plant scale. Extruded and blown films were prepared containing these additives with conventional polymer processing equipment. The mechanical properties were similar to those obtained with laboratory produced compression moulded films.

A systematic review of treatments for atopic dermatitis

Atopic dermatitis is a very common inflammatory skin disease, particularly in children. A systematic review of randomised controlled trials of treatments for atopic dermatitis (AD) was carried out to assess how many trials exist, what they cover, what they do not cover, the research gaps, provide a 'blue print' for future Cochrane Reviews and assist those making treatment recommendations by summarising the available RCT evidence, using descriptive statistics. The Cochrane Collaboration systematic review process formed the basis of the methodology, from which over 4000 studies were located via electronic database searches and hand searching of journals. A total of 292 trials were finally included covering 9 treatment groups and over 48 individual treatments. There are lots of trials covering lots of interventions but gaps are evident. However, there is evidence of a benefit in the treatment of atopic dermatitis with topical corticosteroids, psychological approaches, UV light, ascomycin derivatives, topical tacrolimus and oral cyclosporin. Treatments that show limited evidence of a benefit include non-sedatory antihistamines, topical doxepin, the oral antibiotic Cefadroxil on clinically infected AD, the topical antibacterial Mupirocin on clinically uninfected AD, Chinese herbs, hypnotherapy and biofeedback, massage therapy, dietary manipulation, house dust mite reduction, patient education, emollients, allergen antibody complexes of house dust mite and thymic extracts. Treatments that show no evidence of benefit include sedatory antihistamines, oral sodium cromoglycate, oral antibiotics on clinically uninfected AD, topical antibacterials, topical antifungals, aromatherapy essential oils, borage oil, fish oil, evening primrose oil, enzyme-free clothes detergent, cotton clothing, house dust mite hyposensitisation, salt baths, topical coal tar, topical cyclosporin and platelet-activating-factor antagonist. When interpreting the conclusions of this thesis it is important to understand that lack of evidence does not equal lack of efficacy, particularly considering the interventions that are commonly in use today to treat atopic dermatitis that have not been subjected to RCTs, such as occlusive dressings, water softening devices and stress management among many others.

The behaviour of antioxidants in polyolefins under conditions of U.V. exposure

The effects of antioxidants and stabilizers on the oxidative degradation of polyolefins (low density polyethylene [LDPE] and polypropylene [PPJ have been studied after subjecting to prior high temperature processing treatments. The changes in the both chemical and physical properties of unstabilized polymers occurring during processing were found to be strongly dependent on the amount of oxygen present in the mixer. Subsequent thermal and photo-oxidation showed very similar characteristics and the chromophore primarily responsible for:both thermo and photooxidative degradation of unstabilized polymers was found to be hydroperoxide formed during processing. Removal of hydroperoxide by heat treatment in an inert atmosphere although increasing ketonic carbonyl concentration, markedly decreased the rate of photo-oxidation, introducing an induction period similar to that of an unprocessed sample. It was concluded that hydroperoxides are the most important initiators in normally processed polymers during the early stages of photo-oxidation. Antioxidants such as metal dithiocarbamates which act by destroying peroxides into non-radica1 products were found to be efficient melt stabilizers for polyolefins and effective UV stabilizers during the initial photo-oxidation stage, whilst a phenolic antioxidant, n-octadecyl-3-(3',5'-di-terbutyl 4'hydroxypheny1) propionate (Irganox 1076) retarded photo-oxidation rate in the later stages. A typical 'UV absorber' 2-hydroxy-4-octyloxy-benzophenone (HOBP) has a minor thermal antioxidant action but retarded photo-oxidation at all stages. A substituated piperidine derivative, Bis [2.2.6.6-tetramethylpiperidlnyl-4] sebacate (Tinuvin 770) behaved as an pro-oxidant during thermal oxidation of polyolefins but was an effective stabilizer against UV light. The UV absorber, HOBP synergised effectively with both peroxide decomposing antioxidants (metal dithiocarbamates) and a chain-breaking antioxidant (Irganox 1076) during photo-oxidation of the poymers studed whereas the combined effect was additive during thermal oxidation. By contrast, the peroxide decornposers and chain-breaking antioxidant (Irganox 1076) which were effective synergists during thermal oxidation of LDPE· were antagonistic during photo-oxidation. The mechanisms of these processes are discussed.

Multilayered coated infra-red surface plasmon resonance fibre sensors for aqueous chemical sensing

A series of surface plasmonic fibre devices were fabricated by depositing multiple thin coatings on a lapped section of a standard single mode telecoms fibre forming a D-shaped section and then inscribing a grating-type structure using UV light. The coatings consisted of base coatings of semi-conductor (germanium) and dielectric (silicon dioxide) materials, followed by different metals. These fibre devices showed high spectral refractive index sensitivity with high coupling efficiency in excess of 40 dB for indices in the aqueous regime and below, with estimated index sensitivities of Lambda lambda/Lambda n = 90-800 nm from 1 to 1.15 index range and Lambda lambda/Lambda n = 1200-4000 nm for refractive indices from 1.33 to 1.39. (C) 2009 Elsevier Inc. All rights reserved.

Microstructures made in optical fiber with femtosecond laser

Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching. Integrated with UV-inscribed fiber Bragg gratings, these microstructures have miniature, robustness and high sensitivity features and have been used to implement novel devices for various sensing applications. The fiber microchannels were used to detect the refractive index change of liquid presenting sensitivities up to 7.4 nm/refractive index unit (RIU) and 166.7 dB/RIU based on wavelength and power detection, respectively. A microslot-in-fiber based liquid core waveguide as a refractometer has been proposed and the device was used to measure refractive index, and a sensitivity up to 945 nm/RIU (10-6/pm) was obtained. By filling epoxy in the microslot and subsequent UV light curing, a hybrid waveguide grating structure with polymer core and glass cladding was fabricated. The obtained device was highly thermal responsive, demonstrating a linear coefficient of 211 pm/°C.

Microstructures made in optical fiber with femtosecond laser

Different types of microstructures including microchannels and microslots were made in optical fibers using femtosecond laser inscription and chemical etching. Integrated with UV-inscribed fiber Bragg gratings, these microstructures have miniature, robustness and high sensitivity features and have been used to implement novel devices for various sensing applications. The fiber microchannels were used to detect the refractive index change of liquid presenting sensitivities up to 7.4 nm/refractive index unit (RIU) and 166.7 dB/RIU based on wavelength and power detection, respectively. A microslot-in-fiber based liquid core waveguide as a refractometer has been proposed and the device was used to measure refractive index, and a sensitivity up to 945 nm/RIU (10-6/pm) was obtained. By filling epoxy in the microslot and subsequent UV light curing, a hybrid waveguide grating structure with polymer core and glass cladding was fabricated. The obtained device was highly thermal responsive, demonstrating a linear coefficient of 211 pm/°C.

Molecular and cellular effects of ultraviolet light-induced genotoxicity

Exposure to the solar ultraviolet spectrum that penetrates the Earth's stratosphere (UVA and UVB) causes cellular DNA damage within skin cells. This damage is elicited directly through absorption of energy (UVB), and indirectly through intermediates such as sensitizer radicals and reactive oxygen species (UVA). DNA damage is detected as strand breaks or as base lesions, the most common lesions being 8-hydroxydeoxyguanosine (8OHdG) from UVA exposure and cyclobutane pyrimidine dimers from UVB exposure. The presence of these products in the genome may cause misreading and misreplication. Cells are protected by free radical scavengers that remove potentially mutagenic radical intermediates. In addition, the glutathione-S-transferase family can catalyze the removal of epoxides and peroxides. An extensive repair capacity exists for removing (1) strand breaks, (2) small base modifications (8OHdG), and (3) bulky lesions (cyclobutane pyrimidine dimers). UV also stimulates the cell to produce early response genes that activate a cascade of signaling molecules (e.g., protein kinases) and protective enzymes (e.g., haem oxygenase). The cell cycle is restricted via p53-dependent and -independent pathways to facilitate repair processes prior to replication and division. Failure to rescue the cell from replication block will ultimately lead to cell death, and apoptosis may be induced. The implications for UV-induced genotoxicity in disease are considered.