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M Boulton

Publications and source records attributed to M Boulton.

At least 19 recordsLinked to original sources
PubMed2006

VEGF-A regulates the expression of VEGF-C in human retinal pigment epithelial cells.

AIM: To determine the expression and regulation of vascular endothelial growth factor C (VEGF-C), and its receptor VEGFR-3, in human retinal pigment epithelial (RPE) cells and to consider their angiogenic role in choroidal neovascularisation (CNV). METHOD: The expression of VEGF-C and VEGFR-3 in cultured human RPE was confirmed by immunostaining, PCR, western blotting, and ELISA. Cultured RPE cells were exposed to VEGF-A and glucose and VEGF-C and VEGFR-3 changes in gene expression determined by RT-PCR. Secreted VEGF-C protein in conditioned media from RPE was examined by western blotting and ELISA analysis. The ability of VEGF-C to elicit tube formation in choroidal endothelial cells was assayed by an in vitro Matrigel model. RESULT: VEGF-A and glucose upregulated VEGF-C mRNA expression and increased the secretion of VEGF-C protein into the culture medium. VEGF-A, but not glucose alone, stimulated VEGFR-3 mRNA expression. VEGF-C acted synergistically with VEGF-A to promote in vitro tube formation by choroidal endothelial cells. CONCLUSION: VEGF-A has a critical role in the orchestration of VEGF-C expression in RPE cells and the synergistic action of VEGF-C with VEGF-A may play an important part in the aetiology of CNV.

Cells, Cultured↗
PubMed2005

Evidence of a distinct lipid fraction in historical parchments: a potential role in degradation?

Parchment, a biologically based material obtained from the processed hides of animals such as cattle and sheep, has been used for millennia as a writing medium. Although numerous studies have concentrated on the structure and degradation of collagen within parchment, little attention has been paid to noncollagenous components, such as lipids. In this study, we present the results of biochemical and structural analyses of historical and newly manufactured parchment to examine the potential role that lipid plays in parchment stability. The lipid fraction extracted from the parchments displayed different fatty acid compositions between historical and reference materials. Gas chromatography, small-angle X-ray scattering, and solid-state NMR were used to identify and investigate the lipid fraction from parchment samples and to study its contribution to collagen structure and degradation. We hypothesize that the origin of this lipid fraction is either intrinsic, attributable to incomplete fat removal in the manufacturing process, or extrinsic, attributable to microbiological attack on the proteinaceous component of parchments. Furthermore, we consider that the possible formation of protein-lipid complexes in parchment over the course of oxidative degradation may be mediated by reactive oxygen species formed by lipid peroxidation.

Animals↗
PubMed2005

Angiopoietin concentrations in diabetic retinopathy.

BACKGROUND/AIM: Angiopoietin 1 and 2 interact with vascular endothelial growth factor (VEGF) to promote angiogenesis in animal and in vitro models. Although VEGF concentrations are elevated, there is little information regarding angiopoietin concentration in the vitreous of patients with diabetic retinopathy. METHODS: Angiopoietin concentrations were measured by luminescence immunoassay in vitreous samples from 17 patients with non-proliferative diabetic retinopathy (NPDR) and clinically significant diabetic macular oedema (CSMO), 10 patients with proliferative diabetic retinopathy (PDR), and five patients with macular hole (controls) obtained at pars plana vitrectomy. RESULTS: Angiopoietin 1 concentrations were low in patients with macular hole (median 17 pg/ml) while in NPDR with CSMO they were 2002 pg/ml (range 289-5820 pg/ml) and in PDR 186 pg/ml (range 26-2292 pg/ml). Angiopoietin 2 concentrations in NPDR with CSMO were a median of 4000 pg/ml (range 1341-14 329 pg/ml). For both macular hole and PDR patients angiopoietin 2 was below the limit of detection. CONCLUSIONS: Angiopoietin 2 concentration was twice that of angiopoietin 1 in NPDR with CSMO. Angiopoietin 2 is the natural antagonist of angiopoietin 1 which is thought to act as an anti-permeability agent. The predominance of angiopoietin 2 may allow VEGF induced retinal vascular permeability in patients with CSMO. The relatively low concentration of both angiopoietin 1 and 2 in patients with proliferative diabetic retinopathy may reflect the established nature of the neovascularisation in cases proceeding to vitrectomy.

Adult↗
PubMed2004

Do blue light filters confer protection against age-related macular degeneration?

Age-related macular degeneration (AMD) is a major health problem in the developed world accounting for approximately half of all blind registrations. Current treatment options are unsuitable for the majority of patients and therefore the identification of modifiable risk factors that may inform disease prevention programmes is a priority. This review evaluates the long-held belief that blue light exposure has a role in the pathogenesis of AMD. Laboratory evidence has demonstrated that photochemical reactions in the oxygen-rich environment of the outer retina lead to the liberation of cytotoxic reactive oxygen species (ROS). These ROS cause oxidative stress which is known to contribute to the development of AMD. The precise chromopore that may be involved in the pathogenesis of AMD is unclear but the age pigment lipofuscin is a likely candidate. Its aerobic photoreactivity and adverse effects on antioxidant activity combined with its gradual accumulation over time suggests that its in vivo phototoxicity increases with age despite changes in the absorption characteristics of the crystalline lens. Evidence from animal studies confirms blue light's damaging potential but the results are not directly applicable to macular degeneration in humans. Studies of human macular pigment density and the risk of AMD progression following cataract surgery lend further weight to the hypothesis that blue light exposure has a role in the pathogenesis of AMD but the epidemiological evidence is equivocal. On balance the evidences suggests but does not yet confirm that blue light is a risk factor for AMD. Given the socio-economic impact of this disease and urgent need to identify modifiable risk factors, future work should include a large-scale clinical trial to evaluate the effect of blue blocking filters on AMD progression rates.

Animals↗
PubMed2004

Differences in enquiries to CancerBACUP information service by living arrangements.

The study's aim was to ascertain whether living alone is associated with the use of an independent cancer information service. An Enquirer Record Form is completed for every fifth enquirer to the service; two questions asking whether enquirers, patients, relatives/friends were living alone or with others where asked in association with the routine questions. A total of 552 callers were asked in a 5-week period, 77% of all callers in these categories. The main findings were: (1) the proportion of enquirers living alone was similar to the general population; (2) among enquirers, patients were more likely to live alone than relatives/friends; (3) requests differed by whether living alone and by type of enquirer, for example, significantly more people living with others requested emotional support than those living alone, and this contrast was most marked for patients than relatives/friends. This study, notwithstanding its limitations, highlights some of the differences in the use of a service and demonstrates the complexity of information and support seeking.

Family↗
PubMed2002

The pathogenesis of diabetic retinopathy: old concepts and new questions.

Hyperglycaemia appears to be a critical factor in the aetiology of diabetic retinopathy and initiates downstream events including: basement membrane thickening, pericyte drop out and retinal capillary non-perfusion. More recently, focus has been directed to the molecular basis of the disease process in diabetic retinopathy. Of particular importance in the development and progression of diabetic retinopathy is the role of growth factors (eg vascular endothelial growth factor, placenta growth factor and pigment epithelium-derived factor) together with specific receptors and obligate components of the signal transduction pathway needed to support them. Despite these advances there are still a number of important questions that remain to be answered before we can confidently target pathological signals. How does hyperglycaemia regulate retinal vessels? Which growth factors are most important and at what stage of retinopathy do they operate? What is the preferred point in the growth factor signalling cascade for therapeutic intervention? Answers to these questions will provide the basis for new therapeutic interventions in a debilitating ocular condition.

Diabetes Mellitus↗
PubMed2001

Retinal photodamage.

The retina represents a paradox, in that, while light and oxygen are essential for vision, these conditions also favour the formation of reactive oxygen species leading to photochemical damage to the retina. Such light damage seems to be multi-factorial and is dependent on the photoreactivity of a variety of chromophores (e.g., vitamin A metabolites, lipofuscin, melanin, flavins, porphyrins, carotenoids) endogenous to the retina. The aim of this article is to provide a detailed review of our current understanding of the photochemistry and photobiology of these chromophores and to consider how they may contribute to retinal ageing and pathology.

Adaptation, Physiological↗
PubMed2001

Do men with prostate or colorectal cancer seek different information and support from women with cancer?

Male cancer patients' use of a national cancer information service, their requests and key predictors of these over the period April 1996 to March 1998 are presented, in comparison with women. The most frequent requests of 411 prostate, 162 male and 217 female colorectal cancer patients were similar: site-specific information, emotional support, publications, specific therapies. Research or clinical trials (P < 0.05), diet and nutrition (P < 0.001) requests differed between men with prostate and colorectal cancers; complementary therapies (P < 0.05), prognosis (P < 0.05) requests differed between male and female colorectal cancer patients. Among prostate cancer patients, employed men aged 60+ were more likely to need emotional support than retired men aged 70 +; men < 59 years old were more likely to request publications, but less likely to enquire about specific therapies than others. Among male colorectal cancer patients, employed men were less likely to request site-specific information, but more likely to need emotional support than retired men; patients from geographical areas other than Thames were more likely to request publications; patients from manual classes were less likely to enquire about specific therapies than those from non-manual classes. The complexity of information and support seeking behaviour is demonstrated; no pattern was found among men or in comparison with women. Further research is needed to enable development of services that are appropriate to individual needs and concerns.

Age Distribution↗
PubMed2001

Oxygen modulates the release of urokinase and plasminogen activator inhibitor-1 by retinal pigment epithelial cells.

The aims of this study were to examine the effect of oxygen, in the presence or absence of exogenous growth factors, on the release of plasminogen activators and plasminogen activator inhibitor-1 by cultured human retinal pigment epithelial cells. Antigen and activity levels of urokinase, tissue plasminogen activator and plasminogen activator inhibitor were measured in conditioned media after cells were exposed to three different oxygen environments: hypoxia, normoxia and hyperoxia. Overall proteolytic balance was determined by zymography. The effects of exogenous basic fibroblast growth factor and transforming growth factor-beta were also examined. it was found that retinal pigment epithelial cells released urokinase, tissue plasminogen activator and plasminogen activator inhibitor in measurable quantities. After 48 h, urokinase levels were highest at normoxia, reaching 7.2ng/10(6) cells (+/-2.0 SEM), whereas plasminogen activator inhibitor 1 levels were highest at hyperoxia, reaching 67.5ng/10(6) cells (+/-3.7 SEM). Tissue plasminogen activator levels were minimal (<0.5ng/10(6) cells) and unaffected by both oxygen and growth factors. Overall proteolytic activity was also greatest at normoxia. Fibroblast growth factor stimulated urokinase production dose-dependently, but plasminogen activator inhibitor only minimally. Transforming growth factor-beta stimulated plasminogen activator inhibitor production dose-dependently but urokinase only at higher concentrations. These results suggest that both oxygen tension and growth factors may interact to modulate the proteolytic properties of the human retinal pigment epithelium.

Cells, Cultured↗
PubMed2001

The role of the retinal pigment epithelium: topographical variation and ageing changes.

The retinal pigment epithelium (RPE) is a single layer of post-mitotic cells, which functions both as a selective barrier to and a vegetative regulator of the overlying photoreceptor layer, thereby playing a key role in its maintenance. Through the expression and activity of specific proteins, it regulates the transport of nutrients and waste products to and from the retina, it contributes to outer segment renewal by ingesting and degrading the spent tips of photoreceptor outer segments, it protects the outer retina from excessive high-energy light and light-generated oxygen reactive species and maintains retinal homeostasis through the release of diffusible factors. The ageing characteristics of the RPE suggest that in addition to cell loss, pleomorphic changes and loss of intact melanin granules, significant metabolic changes occur resulting, at least in part, from the intracellular accumulation of lipofuscin. This pigment has been shown to be highly phototoxic and has been linked to several oxidative changes, some leading to cell death. While the aetiology of age-related macular degeneration is complex and is as yet unresolved, it is likely that accelerated ageing-like changes in the RPE play a fundamental role in the development of this condition.

Aging↗
PubMed2001

Investigating women's preferences for intrapartum care: home versus hospital births.

There is an increasing amount of evidence to suggest that the clinical outcomes associated with a home birth for low risk women are at least as good, if not better than, the clinical outcomes associated with giving birth in hospital. If it is the case that there is little or no difference in clinical outcomes between the two modes of delivery, then traditional measures of benefit used in health economics, e.g. quality adjusted life years (QALYs), would detect little or no difference between the alternative modes of delivery. From this, the conclusion would be that the utility values associated with each mode of delivery are similar. However, women may still have clearly defined preferences relating to the way in which maternity care is provided. This paper uses the economic technique of conjoint analysis to assess the relative value attached to several main characteristics associated with the process of maternity care during the intrapartum stage for women who have actively chosen to give birth at home relative to women who have given birth in hospital. It was found that respondents who had chosen a home birth valued continuity of carer, a homely environment and the ability to make their own decisions about what happens during labour and delivery. In contrast, hospital birth respondents placed a relatively high value on access to an epidural for pain relief and not needing to be transferred to another location during labour if a problem arose. The results of the study suggest that women have clearly defined preferences for characteristics associated with the process of intrapartum care that would be unlikely to be detected by traditional benefit measures used in health economics. This finding is important where policy issues relating to aspects of maternity care service delivery are being considered.

Delivery Rooms↗
PubMed2001

Comparison of cerebrospinal fluid transport in fetal and adult sheep.

We quantified cerebrospinal fluid (CSF) transport (conductance) and CSF outflow resistance in late-gestation fetal and adult sheep using two methods, a constant pressure infusion method and a bolus injection technique into the lateral ventricles. No significant differences in CSF conductance (fetus 0.013 +/- 0.002, adult 0.014 +/- 0.003 ml x min(-1) x cm H(2)O(-1)) or CSF outflow resistance (fetus 83.7 +/- 9.8, adult 84.7 +/- 19.7 cm H(2)O x ml(-1) x min) were observed. To confirm CSF transport to plasma in fetal animals, (125)I- or (131)I-labeled human serum albumin (HSA) was injected into the lateral ventricles. The tracer entered fetal plasma with an average mass transport rate of 1.91 +/- 0.47% injected/h (n = 9). In two fetuses, we monitored the tracer appearance in plasma and cervical and thoracic duct lymph after injection of radioactive HSA into the ventricular CSF. As was the case in adult animals, fetal tracer concentrations increased in all three compartments over time, with the highest concentrations measured in lymph collected from the cervical lymphatics. These results 1) indicate that global CSF transport parameters in the late-gestation fetus and adult sheep are similar and 2) suggest an important role for extracranial lymphatic vessels in CSF transport before birth.

Animals↗
PubMed2001

Loss of the antiangiogenic pigment epithelium-derived factor in patients with angiogenic eye disease.

Retinal neovascularization characterizes proliferative diabetic retinopathy (PDR). Pigment epithelium-derived factor (PEDF) has been shown to be a major antiangiogenic growth factor in the mammalian eye. PEDF expression is suppressed by hypoxia, and changes in PEDF have been correlated to the development of retinal neovascularization in animal models of hypoxic eye disease. However, whether this concept of a reduced angiogenesis inhibitor holds true in humans is as yet unclear. In this study, we analyzed the in vivo regulation of PEDF in patients with and without hypoxic eye disease. We used immunoblots to measure PEDF in ocular fluids obtained from 64 nondiabetic and diabetic patients. In addition, immunohistochemistry of PEDF was carried out in specimens of normal human retinas and retinas with various degrees of diabetic retinopathy. The PEDF concentrations in patients with PDR (P < 0.001) or extensive nondiabetic retinal neovascularization caused by retinal-vein occlusion (P < 0.001) were lower than in control patients. Levels of PEDF were replenished in PDR patients with previous retinal scatter photocoagulation compared with PDR patients without previous photocoagulation (P = 0.01). Immunohistochemistry revealed an interstitial staining pattern as expected for a secreted protein, with an intense staining in retinas of patients without proliferative eye disease. However, in patients with PDR, little or no staining was detectable. Our data strongly support the concept that retinal angiogenesis is induced by loss of the major angiogenesis inhibitor in the eye, PEDF, in combination with an increased expression of angiogenic growth factors such as vascular endothelial growth factor. Our findings suggest that substitution of angiogenesis inhibitors may be an effective approach in the treatment of PDR.

Aged↗
PubMed2001

Inhibition of RPE lysosomal and antioxidant activity by the age pigment lipofuscin.

PURPOSE: To determine whether lipofuscin is detrimental to lysosomal and antioxidant function in cultured human retinal pigment epithelial (RPE) cells. METHODS: Isolated lipofuscin granules were fed to confluent RPE cultures and the cells maintained in basal medium for 7 days. Parallel cultures were established that did not receive lipofuscin. Cultures were either exposed to visible light (390-550 nm) at an irradiance of 2.8 mW/cm(2) or maintained in the dark at 37 degrees C for up to 24 hours. Cells were subsequently assessed for cell viability, lysosomal enzyme activity, and antioxidant capacity. RESULTS: There was no loss of cell viability during the first 3 hours of light exposure, whereas a 10% loss of viability was observed in lipofuscin-fed cultures after 6 hours' exposure to light. Activities of acid phosphatase, N-acetyl-beta-glucuronidase, and cathepsin D were decreased by up to 50% in lipofuscin-fed cells exposed to light compared with either unfed cells or cells maintained in the dark. There was also a decrease in the antioxidant potential of RPE cells. Catalase and superoxide dismutase activities decreased by up to 60% and glutathione levels by 28% in light-exposed lipofuscin-fed cells compared with unfed cells or cells maintained in the dark. CONCLUSIONS: Lipofuscin has the capacity to reduce the efficacy of the lysosomal and antioxidant systems in RPE cells that may play an important role in retinal ageing and the development of age-related macular degeneration.

Acid Phosphatase↗
PubMed2000

Cancer patients' information needs and information seeking behaviour: in depth interview study.

OBJECTIVES: To explore why cancer patients do not want or seek information about their condition beyond that volunteered by their physicians at times during their illness. DESIGN: Qualitative study based on in-depth interviews. SETTING: Outpatient oncology clinics at a London cancer centre. PARTICIPANTS: 17 patients with cancer diagnosed in previous 6 months. MAIN OUTCOME MEASURES: Analysis of patients' narratives to identify key themes and categories. RESULTS: While all patients wanted basic information on diagnosis and treatment, not all wanted further information at all stages of their illness. Three overarching attitudes to their management of cancer limited patients' desire for and subsequent efforts to obtain further information: faith, hope, and charity. Faith in their doctor's medical expertise precluded the need for patients to seek further information themselves. Hope was essential for patients to carry on with life as normal and could be maintained through silence and avoiding information, especially too detailed or "unsafe" information. Charity to fellow patients, especially those seen as more needy than themselves, was expressed in the recognition that scarce resources-including information and explanations-had to be shared and meant that limited information was accepted as inevitable. CONCLUSIONS: Cancer patients' attitudes to cancer and their strategies for coping with their illness can constrain their wish for information and their efforts to obtain it. In developing recommendations, the government's cancer information strategy should attend to variations in patients' desires for information and the reasons for them.

Adaptation, Psychological↗
PubMed2000

[A retinoid constituent of lipofuscin, A2-E, is a photosensitizer in human retinal pigment epithelial cells].

BACKGROUND: A fluorescent compound of lipofuscin, A2-E, has been shown to impair lysosomal function and to increase the intralysosomal pH of human retinal pigment epithelial (RPE) cells. This study addressed the phototoxic potential of A2-E on RPE cells. METHODS: A2-E accumulation was confirmed by fluorescence microscopy and fluorescence-activated cell sorter analysis. Acridine orange staining allowed assessment of lysosomal integrity and intralysosomal pH. Phototoxic properties of A2-E were determined by exposing A2-E-free and A2-E-fed RPE cell cultures to short-wavelength visible light and assessing cell viability and lysosomal integrity. RESULTS: Intralysosomal accumulation of A2-E was confirmed. Acridine orange staining showed that the A2-E was located in the lysosomal compartment and induced an elevation of intralysosomal pH. Exposure of A2-E fed cells to light resulted in a significant loss of cell viability by 72 h which was not observed in either RPE cells maintained in the dark or A2-E-free cultures exposed to light. Toxicity was associated with a loss of lysosomal integrity. CONCLUSION: A2-E is detrimental to RPE cell function by a variety of mechanisms including inhibition of lysosomal degrading capacity, loss of membrane integrity, and phototoxicity. Such mechanisms could contribute to retinal aging and to retinal diseases associated with excessive lipofuscin accumulation.

Cell Survival↗
PubMed2000

Regulation of tyrosinase expression and activity in cultured human retinal pigment epithelial cells.

The purpose of this study was to investigate the regulation of tyrosinase gene expression and activity in cultured human retinal pigment epithelial (RPE) cells. The tyrosinase promoter (Ty.prom) region (400 bp) was PCR amplified and cloned into a modified mammalian expression vector (pcDNA3.1) upstream of a firefly luciferase (Luc) cDNA and was designated 'pcDNA3.1-Ty.prom.Luc'. The plasmid was co-transfected into RPE cells with a second mammalian expression plasmid (pRL-TK) containing a herpes simplex virus thymidine kinase promoter region upstream of Renilla Luc in a protocol designated the 'dual luciferase assay' (DLA). After co-transfection, cells were treated with a range of potential melanogenic agents; basic fibroblast growth factor (bFGF), methyl methane sulphonate, alpha-melanocyte stimulating hormone, verapamil, phorbol myristate acetate, cholera toxin (CT), pigment epithelium derived factor (PEDF), and L-tyrosine. The expression of tyrosinase promoter and enzymatic activities were determined 48 hr post-transfection using the DLA and DOPA oxidase assays, respectively. Tyrosinase activity could not be detected in RPE cells with any of the treatments. Tyrosinase promoter activity was significantly up-regulated in RPE cells treated with bFGF, PEDF, verapamil, CT and tyrosine compared with control cells. In conclusion, the tyrosinase gene is not only expressed but can be regulated in response to different chemicals in cultured human RPE cells. However, it appears that RPE cells in culture lack a post-transcriptional and/or translational modification point(s), which are necessary for tyrosinase enzymic activity.

Adjuvants, Immunologic↗