No description available.

Humans are trichromatic, and yet their perception of colours is rich and complex. The research presented in this thesis explores the process of colour appearance of uniform patches and natural polychromatic stimuli. This is done through the measurement and analysis of the achromatic locus (Chapter 2), modelling of chromatic adaptation in a large dataset of unique hues settings (Chapter 3), and measurement of thresholds for uniform and polychromatic stimuli derived from simulated skin images (Chapter 4). Chapter 2 proposes a novel navigation scheme based on unique hues for traversing colour space. The results show that when colour adjustments are made using this novel scheme, the variability of achromatic settings made by observers is reduced compared to the classical method of making colour adjustments along the cardinal axes of the CIELUV colour space. This result holds across the tested luminance levels (5,20,50 cd/m^2) in each of the three tested ambient illumination conditions – dark, simulated daylight and cool white fluorescent lighting. The analysis also shows that the direction of maximum variance of the achromatic settings lies along the daylight locus. Chapter 3 evaluates models of chromatic adaptation by using unique hues settings measured under different ambient illumination conditions. It is shown that a simple diagonal model in cone excitation space is the most efficient in terms of the trade-off between accuracy and degrees of freedom. It is also found that diagonal and linear models show similar performances, reiterating their theoretical equivalence. Performances of these diagonalisable models are found to be worse for UR and UG unique hue planes compared to UY and UB planes. Chapter 4 presents a set of three experiments reporting estimations of perceptual thresholds for polychromatic and uniform stimuli in a 3-D chromaticity-luminance colour space. The first experiment reports thresholds for simulated skin images and uniform stimuli of the corresponding mean CIELAB colour. The second and third experiments investigate the effect of ambient illumination and the location of the stimuli in colour space. The thresholds for the polychromatic stimuli are found to be consistently higher than those for the uniform patches, for both the chromatic, and the luminance projections. The area of the chromaticity ellipses shows a gradual increase with distance from the illuminant chromaticity. The orientations of these ellipses for simulated skin are found to align with the vector joining the mean patch chromaticity and the illuminant chromaticity.

Psoriasis represents a complex interplay between genetic predisposition, the environment and inflammatory responses, and increasing evidence suggests alterations in the epigenome, including histone acetylation, plays a role. Bromodomain-containing proteins regulate gene expression by binding to acetyl-lysine residues on histones and recruiting transcription factors to gene regulatory regions. The development of small molecule inhibitors of bromodomain extraterminal (BET) proteins has enabled interrogation of this pathway. Interestingly BET inhibitors demonstrate anti-proliferative and anti-inflammatory effects in in vitro and in vivo models of cancer and inflammation. An established in-vitro keratinocyte model of cutaneous inflammation was further developed to characterise IL-6 and IL-8 (mRNA and protein) responses to TNF+ IL-17 stimulation. Chromatin immunoprecipitation (ChIP) studies showed psoriasis-relevant stimuli induced dynamic, gene-specific alterations of the epigenome, including histone hyperacetylation, with co-ordinated recruitment of BET proteins (Brd2, Brd3 and Brd4) and RNA polymerase II, to the promoter region of IL-6 and IL-8. The effects of TNF+ IL-17 stimulation in keratinocytes were validated through global gene expression array studies which showed stimulation modulated expression of keratinocyte genes known to be differentially expressed in psoriasis and involved in its pathogenesis. The hypothesis that BET proteins are involved in regulating inflammatory responses in keratinocytes was tested using a specific BET inhibitor, I-BET151; this blocked pathogenic inflammatory responses. In particular, IL-6 and IL-8 responses to TNF + IL-17 stimulation demonstrated potent sensitivity to I-BET151 treatment; this could be accounted for by the decreased binding of BET proteins and RNA polymerase II to IL-6 and IL-8 gene promoter regions in the presence of the BET inhibitor. Global gene expression array studies showed genes sensitive to BET inhibition were primarily involved in the cell cycle and inflammation, with many relevant to the pathogenesis of psoriasis. In addition, ~20% of genes identified in a previously published meta-analysis of five psoriasis transcriptomic studies were differentially modulated by I-BET151 treatment in TNF + IL-17 stimulated NHEKs. Furthermore, acetate, a principle metabolite of ethanol, a factor implicated in the development and exacerbation of psoriasis, enhanced IL-6, but not IL-8, responses to TNF + IL-17 stimulation through gene-specific epigenetic modifications at the promoter region. IFN also enhanced IL-6, but not IL-8, response to TNF + IL-17 stimulation, suggesting i) IL-6 is more sensitive to enhancement by additional disease relevant stimuli and ii) IL-6 and IL-8 are differentially regulated at the transcriptional level; ChIP studies showed increased enrichment of Brd4/p65 at the IL-6 promoter compared to the IL-8 promoter.

Once considered fairly harmless due to its low energy UVA is now considered a class one carcinogen, the ability of UVA alone to induce Non-melanoma skin cancer is well accepted and although more controversial there is now significant evidence from epidemiological studies and animal models to suggest a role for UVA in the development of melanoma. Furthermore due to its high penetrance UVA is thought to play a larger role in photoaging than UVB. Despite this current sum protection methods assess UVA protection only as a ratio of UVA: UVB that is blocked by the sun cream. Therefore it is desirable to have a more biologically relevant method to assess UVA protection offered by a sun cream. The work in this thesis focuses on the identification of a robust biomarker of UVA exposure, with the aim to identify biomarkers of UVA that could be used to assess the protection offered by different sun creams in order to develop a method in assessing protection similar to SPF that is currently used for UVB. The primary focus was on looking at the DNA damage response following UVA irradiation, and the data presented here shows distinct differences in the mechanism underpinning the DNA damage response in directly irradiated cells and in the UVA bystander cells. The response following UVA has also been shown to be distinct to that following UVB irradiation, both in terms of the DDR and apoptosis induction.

No description available.

No description available.

In an attempt to identify the genetic determinants of psoriasis a genome wide screen (GWS) with microsatellites was performed on a collection of multiplex families. Ten microsatellites were identified that generated evidence of linkage to psoriasis susceptibility loci. Support of linkage was observed to markers in the major histocompatibility complex (MHC) and to markers on chromosomes 2, 8 and 20 in an independent collection of families. These data indicated that the primary genetic determinant for psoriasis was located in the MHC, a region historically observed to be associated with psoriasis in case/control studies. Fine mapping of this region has produced strong evidence that the susceptibility locus lies within a 285 kb region defined by HLA-C and the microsatellite TN62. The three non-MHC linkages were screened in a large collection of ASP families, although none received additional support of linkage. The families were partitioned upon the basis of allele sharing at the MHC. Those families that exhibited linkage to the MHC (TN3 families) generated evidence of linkage to chromosome 20, suggesting an interaction between the susceptibility locus in this interval with the major locus in the MHC. A YAC contig was constructed for this region and two candidate genes were excluded from this interval. Two novel microsatellites were cloned from this contig although neither failed to generate evidence of linkage or association to a susceptibility gene. A secondary GWS was performed upon a large collection of families, although this failed to generate evidence of linkage to any novel susceptibility loci or to provide support for previously identified putative loci, except to markers on the MHC. Upon partitioning of this dataset, the TN3 families generated evidence of linkage to markers on chromosome 1. Those families not exhibiting linkage to the MHC (TNX families) generated evidence of linkage to three further novel regions.

Pressure ulceration remains a significant problem within healthcare and over recent years has been elevated to a position of priority within national quality improvement agendas. This thesis will contextualise key issues, determine barriers and facilitators in relation to pressure ulcer prevention and make recommendations for service improvement. Several methodologies were used to explore different aspects of the structure, process and outcome measures involved with pressure ulcer prevention. Initially a retrospective data analysis reviewed incidence, reporting and validation of hospital acquired pressure damage. This showed the importance of a robust reporting and validation system. Qualitative methods were then used with staff throughout the organisational hierarchy to explore values and beliefs about pressure ulcer prevention. This showed that the context and key drivers behind the pressure ulcer prevention quality initiative were highly valued by those in positions of seniority. The ‘feedback loop’ was also viewed as of paramount importance by those in key positions of responsibility, but did not appear to be valued equally by clinically based ward staff. The importance of cohesive multidisciplinary ‘teamwork’ was valued by all levels of staff and equally ‘education and documentation’ were described as key facets of preventative care. ‘Accountability’ with regards to responsibility and ownership was also highlighted however a variation in views was evident among different staff groups. Whilst a high priority was attributed to pressure ulcer prevention by everyone, competing interests meant that this fundamental aspect of care was frequently delegated to healthcare assistants with no formal training in this area of practice. An experimental study design was therefore used to evaluate the efficacy of an educational intervention for healthcare assistants. Results show that training has improved knowledge levels, attitude and self-report of clinical practice. It is recommended that further research is conducted to substantiate the findings.

Capillary Vascular Malformations (CMs) or Port Wine Stains are a congenital abnormality of the dermal vasculature that results in the skin having a pink to purple colouration. This thesis examines the development of the videomicroscopy as a non-invasive tool to examine the vessel structure of CMs in vivo. A number of studies have been undertaken including: 1. the use of colour filtering as an adjunct to videomicroscopy; 2. the development and validation through a biopsy study of a Depth Measuring Videomicroscope (DMV); 3. the description of vessel change following a single laser treatment using DMV; 4. the relationship between location and colour of a CM and vessel structure; 5. the effect of prolonged laser treatment on vessel structure; and 6. the effect of using new generation Pulsed dye lasers on CM vessel structure and their efficacy. Colour filtering appears to reduce the artefact from the reflection of light from the skin surface. The development of the Depth Measuring Videomicroscope (DMV), however, reduces this reflection and colour filtering is not required. The DMV can be used to measure the diameter and depth of Capillary Vascular Malformations (CM) in vivo and this has been validated against biopsy measurements using a Bland and Altman Test. Following laser treatment the larger and more superficial capillaries are successfully treated leaving the deeper (p<0.02) and smaller vessels (p<0.001).This occurs both after a single laser treatment and prolonged treatment. To improve the treatment of CMs resistance to standard pulsed dye laser treatment the capillary characteristics of resistant CMs were studied prior to treatment were newer generation pulsed dye lasers. Although, the optimum treatment parameters for a particular malformation could not be predicted from this study, 595nm wavelength, 1.5 ms pulse duration and 14 j/sqcm fluence appeared to be the most successful settings.

The present studies were undertaken to develop and validate acute and chronic models of itch in mice, based on the combined use of behavioural tests in awake mice and <i>in vivo</i> electrophysiological recordings from itch afferents in anaesthetized animals. The hypothesis was that scratching behaviour can be evoked in mice using intradermal injections of pruritogenic drugs and that this can be measured automatically and objectively to provide a reliable indicator of itch. A further hypothesis was that electrophysiological recordings made <i>in vivo</i> from murine cutaneous sensory nerves can be used to distinguish between pruritogens and algogens. The model of itch that was developed is based on injection of histamine into the back of the mouse neck to evoke scratching of the area by the hind paws. The studies demonstrated that scratching in mice can be induced using histamine and other pruritogens (e.g. trypsin and 5-HT) in a reproducible dose dependent manner. Scratching was established as a response to itch-provoking agents, but not to painful stimuli. A novel mechanism of histamine evoked scratching involving H₄ receptors was discovered. Chronic itching in response to topical application of dinitrochlorobenzene was also established. A robust automated method for the detection and measurement of scratching in mice was developed, which considerably enhances accuracy and reduces the time taken, in comparison with manual observation of scratching. <i>In vivo</i> electrophysical recordings showed that pruritogens evoke a pattern of response in cutaneous nerves distinct in nature from that evoked by algogenic stimuli. However, nerves responded to both stimuli, suggesting that in mice, there are probably no independent ‘pruritoceptos’, unlike the situation in man. In summary, scratching in mice can be recorded automatically and used as a reproducible quantitative measure of itch.