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Biomedical subjects

M Boulton

Publications and source records attributed to M Boulton.

At least 73 records · Page 4Linked to original sources
PubMed1996

Qualitative research in health care: I. The scope and validity of methods.

It is increasingly argued that qualitative approaches have an important role in health care research. A wide range of methods are used to collect qualitative data, including in-depth interviews, focus groups and observational methods such as participant observation. The reliability and validity of qualitative studies can be addressed by a variety of techniques. Although there is less consensus about appropriate methods of analysing qualitative data, such analyses tend to be grounded in the data, and involve iterative procedures and the development and refinement of typologies, analogies and other forms of concept to make sense of data.

Data Collection↗
PubMed1996

Qualitative research in health care: II. A structured review and evaluation of studies.

A hand search of the original papers in seven medical journals over 5 years was conducted in order to identify those reporting qualitative research. A total of 210 papers were initially identified, of which 70 used qualitative methods of both data collection and analysis. These papers were evaluated by the researchers using a checklist which specified the criteria of good practice. Overall, 2% of the original papers published in the journals reported qualitative studies. Papers were more frequently positively assessed in terms of having clear aims, reporting research for which a qualitative approach was appropriate and describing their methods of data collection. Papers were less frequently positively assessed in relation to issued of data analysis such as validity, reliability and providing representative supporting evidence. It is concluded that the full potential of qualitative research has yet to be realized in the field of health care.

Data Collection↗
PubMed1996

Drainage of CSF through lymphatic pathways and arachnoid villi in sheep: measurement of 125I-albumin clearance.

We investigated lymphatic drainage pathways of the central nervous system in conscious sheep and quantified the clearance of a cerebrospinal fluid (CSF) tracer into lymph and blood. In the first group of studies, 125I-HSA was injected into the lateral ventricles of the brain or into lumbar CSF and after 6 h, various lymph nodes and tissues were excised and counted for radioactivity. Multiple lymphatic drainage pathways of cranial CSF existed in the head and neck region defined by elevated 125I-HSA in the retropharyngeal/cervical, thymic, pre-auricular and submandibular nodes. Implicated in spinal CSF drainage were mainly the lumbar and intercostal nodes. In a second group of experiments, multiple cervical vessels and the thoracic duct were cannulated and lymph diverted from the animals. Transport of tracer through arachnoid villi was taken from recoveries in venous blood. Following intraventricular administration, the 6 h recoveries of 125I-HSA in the lymph (sum of cervical and thoracic duct) and blood were 8.2% +/- 3.0 and 12.5% +/- 4.5 respectively and at 22 h, 25.1% +/- 6.9 and 20.8% +/- 4.1 respectively. When 125I-HSA was injected into lumbar CSF, the 6 h recoveries of tracer in thoracic duct and blood were 11.6% +/- 2.7 and 16.3% +/- 3.7 respectively. Total lymph and blood recoveries were not significantly different in any experiment. We conclude that the clearance of 125I-HSA from the CSF is almost equally distributed between lymphatic and arachnoid villi pathways.

Animals↗
PubMed1996

The effect of scatter laser photocoagulation on intravitreal levels of growth factors in the miniature pig.

PURPOSE: To characterise changes in intravitreal growth factor profiles following retinal photocoagulation in the miniature pig. METHODS: Miniature pig eyes underwent scatter photocoagulation by either diode infrared or emerald green laser. Animals were sacrificed at various times (up to 42 days) post-laser. The eyes were than removed and vitreous samples analysed for basic fibroblast growth factor, insulin-like growth factor-I and epidermal growth factor by radioimmunoassay, transforming growth factor-beta 2 by ELISA and insulin-like growth factor binding proteins using Western ligand blotting. RESULTS: Vitreous transforming growth factor-beta 2 levels were decreased at 1 h post diode laser and at 4 and 7 days post emerald laser but returned to normal by 21 and 42 days respectively. Vitreous insulin-like growth factor-I levels increased at 4 and 7 days post diode and emerald laser respectively but returned to normal by 21 days. Insulin-like growth factor Western ligand blotting demonstrated that a 34 kDa insulin-like growth factor binding protein was predominant in the pig vitreous; the levels of this binding protein followed an identical trend to those observed for insulin-like growth factor-I. No changes in vitreous levels of either basic fibroblast growth factor or epidermal growth factor were observed following laser treatment. CONCLUSIONS: Our results demonstrate a significant shift in the balance of intravitreal growth factors following retinal laser photocoagulation. Such changes may be pertinent to the regression of preretinal new vessels after laser photocoagulation.

Animals↗
PubMed1996

Oxygen modulates the response of the retinal pigment epithelium to basic fibroblast growth factor and epidermal growth factor by receptor regulation.

PURPOSE: To determine if low oxygen affects growth factor responsiveness in retinal pigment epithelial (RPE) cells and if such effects are mediated through changes in cell surface receptors. METHODS: Proliferating human RPE cells were exposed to varying concentrations of exogenous basic fibroblast growth factor (bFGF) or epidermal growth factor (EGF) at different media oxygen tensions (16 to 147 mm Hg) and cell counts determined after 4 days. Receptor expression was determined by affinity cross-linking and saturation binding studies on confluent RPE cultures exposed to varying media oxygen tensions for 2 days. RESULTS: Retinal pigment epithelial cells exhibited a greater proliferative response to exogenous growth factors at hypoxia than at higher media oxygen tensions, and they expressed bFGF and demonstrated that hypoxia caused both an increase in the number of EGF receptors per cell and a shift from low to high affinity receptors. CONCLUSIONS: These results suggest that hypoxia not only can stimulate RPE cell proliferation per se, it also can "prime" cells t respond more markedly to exogenous growth factors. These observations may be important in elucidating the cause of proliferative vitreoretinopathy.

Cell Count↗
PubMed1996

The views of general practitioners on community carrier screening for cystic fibrosis.

BACKGROUND: Recent developments in molecular genetics have made it possible to identify carriers of the cystic fibrosis (CF) mutation, regardless of family history, before they have an affected child. Using these techniques, population or 'community' carrier screening can offer informed reproductive choice to individuals and couples who would not otherwise know of their risk of having a CF child. AIM: This study set out to assess the views of general practitioners (GPs) on community carrier screening for CF and to consider the factors that influence their willingness to offer it themselves. METHOD: A self-administered questionnaires was sent to all 616 GPs in four areas of North Thames (West) Region. RESULTS: Two-thirds of respondents indicated that identifying carrier couples to offer genetic counselling before conception was a very important benefit of community carrier screening. Two-thirds felt that general practice was the most appropriate place in which to offer it, and similar proportions that the most appropriate times to do so were when a close relative was diagnosed and when seeking family planning. About half wanted to offer community carrier screening themselves; this was related to experience with CF patients and CF carrier testing, and estimates of the numbers of CF carriers in the practice. CONCLUSIONS: There is considerable support among GPs for community carrier screening for CF in general practice, particularly in the context of family planning services. Knowledge and experience of CF increase GPs' willingness to offer it themselves.

Attitude of Health Personnel↗
PubMed1995

Oxygen modulates production of bFGF and TGF-beta by retinal cells in vitro.

Vasoproliferative retinopathies result from retinal capillary non-perfusion and consequent inner retinal hypoxia. However, it is not known whether oxygen mediates vasoproliferation directly (at the nuclear level) or indirectly by regulating the production of growth factors. We have investigated the effect of oxygen on the production of basic fibroblast growth factor and transforming-growth-factor-beta by a variety of retinal cell types in culture. Confluent cultures were maintained for 48 hr under varying oxygen tensions ranging from 135 to 18 mmHg. A reduction in basic fibroblast growth factor levels was observed in the cell lysates and extracellular matrix from retinal microvascular endothelial cell, retinal microvascular pericyte and retinal pigment epithelial cell cultures when the oxygen tension of the medium was reduced from 135 to 18 mmHg. Levels of basic fibroblast growth factor in conditioned media from microvascular endothelial and retinal pigment epithelial cell cultures also decreased when the oxygen tension of the medium was reduced from 135 to 18 mmHg. Total transforming-growth-factor-beta (and specifically isoforms 1 and 2) in the conditioned media from all three cell types was similarly modulated by oxygen i.e. it decreased as the oxygen tension of the medium was reduced from 135 to 18 mmHg. In contrast, the steady state messenger RNA levels for both basic fibroblast growth factor and transforming-growth-factor-beta 1 genes in RPE cells increased significantly when the oxygen tension of the medium was reduced from 135 to 18 mmHg. These results support the putative role of oxygen in influencing the balance of growth factors during the development of preretinal new vessels.

Blotting, Northern↗
PubMed1995

Gay men's accounts of unsafe sex.

This paper provides a qualitative analysis of the explanations given by a sample of 78 gay men in England of the most recent occasion on which they engaged in anal intercourse without a condom. Explanations are analysed and interpreted from the sociological perspective of 'accounts': that is, they are not viewed as exact descriptions of the 'real' motives for behaviour but are seen as a powerful resource that can illuminate the knowledge, assumptions and values that inform behaviour. Four distinct types of accounts were identified from the men's descriptions of the circumstances and motivations surrounding their most recent unsafe sexual encounter. These related to: (i) their emotional needs and drives; (ii) the calculus of risk; (iii) issues of trust; and (iv) lapses of control. Each of these types of account is described and the implications of the typology are considered, both for our understanding of the meanings, considerations and constraints surrounding high-risk sexual behaviour and for developing more relevant health education interventions.

Adolescent↗
PubMed1995

Hypoxia induces HSP 70 gene expression in human hepatoma (HEP G2) cells.

Populations of cells within solid tumours are exposed to low oxygen concentrations. The mechanism by which tumour cells tolerate such hypoxia is unknown but it may parallel responses to other types of cellular stress. We investigated the effect of oxygen on steady state levels of inducible heat shock protein 70 mRNA in cultured human hepatoma cells. Northern blot analysis demonstrated that hypoxia increased HSP 70 mRNA levels within 3 hours, with a transient 12-fold increase at 6 hours compared with normoxia. We also showed that heat shock induced a 20-fold increase in HSP 70 mRNA. This data suggests that HSPs may be important in tumour progression by protecting cells from hypoxic stress.

Blotting, Northern↗
PubMed1994

Regular partners and risky behaviour: why do gay men have unprotected intercourse?

Studies in both the UK and the USA continue to show that gay and bisexual men put themselves at risk of exposure to HIV through unprotected intercourse, most often with regular partners. As part of a larger study of homosexually active men, 310 men who had had unprotected anal intercourse with a man in the previous year were asked to describe the last occasion on which this had happened. The majority of men had had unprotected intercourse with a regular partner and did not perceived it as risky, although most did not know the HIV status of their partner. Regular and non-regular partners were perceived differently. Men were more likely to be emotionally involved in regular partners and to perceive unprotected penetrative sex with a regular partner as not risky. Future health education initiatives must take into account men's emotional involvement in regular partners and their perception of unprotected intercourse with such partners as not risky.

Adolescent↗
PubMed1994

Regional variation and age-related changes of lysosomal enzymes in the human retinal pigment epithelium.

In this study the activities of two lysosomal enzymes in retinal pigment epithelial (RPE) cells isolated from three regions of the human fundus were examined: the macula, the nasal midzone, and the periphery. The results obtained showed that the activities of acid phosphatase and cathepsin D were significantly higher in the RPE cells derived from the macular region when compared with those in the periphery. The values for the midzone appeared to be intermediate between the other two regions. Furthermore, the overall activity of both enzymes increased as a function of age.

Acid Phosphatase↗
PubMed1994

Production of IGF-I and IGF binding proteins by retinal cells in vitro.

Insulin-like growth factor I (IGF-I) and its associated binding proteins (IGFBPs) have been identified in retinal tissues but their precise cellular origin remains unclear. The aim of this study was to examine the ability of three retinal cell types (microvascular endothelial cells, pericytes, and pigment epithelial cells) and a non-retinal cell type (Tenon's fibroblasts) to produce IGF-I and cell specific IGFBPs in vitro. Using a radioimmunoassay we demonstrated that all four cell types produce IGF-I and that this production continued over a 72 hour period. In addition, western ligand blotting revealed that each cell type produced at least one IGFBP and that each cell type produced a different IGFBP profile. Endothelial cells produced a 24 kDa band only, pericytes produced both a 24 kDa and a 34 kDa band, retinal pigment epithelial cells produced a 38-41 kDa band, while fibroblasts produced both a 24 kDa and a 30 kDa band. Laser scanning densitometry demonstrated that in the majority of experiments the IGFBPs accumulated in the culture medium over a 72 hour period. Neither IGF-I nor IGFBPs were observed in cell lysates indicating de novo synthesis and secretion in vitro. These results suggest an autocrine/paracrine function for IGF-I and its associated binding proteins which may play a significant role in both retinal physiology and disease.

Blotting, Western↗
PubMed1994

Retinal and preretinal localisation of epidermal growth factor, transforming growth factor alpha, and their receptor in proliferative diabetic retinopathy.

A number of growth factors have been implicated in the development and perpetuation of preretinal fibrovascular membranes in patients with proliferative diabetic retinopathy (PDR). The aim of this study was to determine the potential role of epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), and their receptor (EGF-R) in PDR development. Immunostaining for EGF, TGF-alpha, and EGF-R was compared between normal retina, PDR retina, and PDR preretinal membranes. Weak staining for EGF and EGF-R was observed throughout the neural retina from non-diabetic eyes while weak to moderate staining for TGF-alpha was observed in the ganglion cell layer and the inner and outer nuclear layers. In contrast, intense staining for EGF and TGF-alpha and moderate staining for EGF-R were observed throughout the PDR retina. Immunoreactivity for EGF, TGF-alpha, and EGF-R was seen in the majority of the 11 excised membranes studied and, though variable, was generally greater than that observed in normal retinas. These results suggest an autocrine/paracrine role for EGF, TGF-alpha, and EGF-R in PDR.

Diabetic Retinopathy↗
PubMed1994

Oxygen regulation of TGF-beta 1 mRNA in human hepatoma (Hep G2) cells.

Solid tumours comprise populations of cells whose behaviour is thought to be influenced by growth factors and the local oxygen environment. We investigated the effect of oxygen on steady state levels of transforming growth factor-beta 1 mRNA in cultured human hepatoma cells. Northern blot analysis demonstrated that hypoxia mediated an early and sustained induction of TGF-beta 1 mRNA above that seen at higher oxygen tensions. The data suggests that modulation of TGF-beta 1 expression by the local oxygen environment may be important in tumour development and progression.

Blotting, Northern↗
PubMed1994

Membrane-bound carbonic anhydrase in human retinal pigment epithelium.

PURPOSE: Inhibition of carbonic anhydrase (CA) by acetazolamide causes a decrease in the standing potential of the retinal pigment epithelium (RPE) and an increase in the rate of subretinal fluid absorption, and it may improve cystoid macular edema. These effects are thought to be mediated by the RPE. Given the solubility coefficient of acetazolamide, the drug is most likely to act by direct inhibition of membrane-bound CA (CA IV). To identify a substrate for acetazolamide in the RPE, the distribution of CA activity and the isoform of CA in the RPE membrane were investigated. METHODS: Carbonic anhydrase activity was determined by Hansson's technique in fresh human eyes from donors of both sexes and different ages. The presence of the membrane-bound isoform CA IV was investigated immunohistochemically at the light and electron microscopic level, as well as by Western blotting in fresh RPE, and in adult and fetal RPE cultures. RESULTS: Hansson's histochemical method demonstrated CA activity on the apical and basolateral cell membrane of the RPE. Using the gamma-globulin fraction of a polyclonal antibody against pure CA IV, immunocytochemistry showed labeling for CA IV on the apical RPE membrane or morphologically polarized human adult and fetal RPE cultures. Gel electrophoresis and Western blotting demonstrated a major immunoreactive band at 55 kDa in homogenates, which was consistently reduced to approximately 35 kDa by incorporation of 0.1% Triton X-100 detergent. CONCLUSIONS: These results suggest that the clinical effects of carbonic anhydrase inhibitors on RPE function may be mediated via membrane-bound carbonic anhydrase activity in RPE and that CA IV is responsible for activity on the apical surface.

Adolescent↗
PubMed1994

Awareness of sexual partners' HIV status as an influence upon high-risk sexual behaviour among gay men.

OBJECTIVE: To evaluate the extent to which 'high-risk' sexual behaviour is influenced by awareness of partners' HIV status among gay men. DESIGN: Structured interviews and collection of saliva samples for anonymous linked testing for HIV-1 antibodies. SETTING: Genitourinary medicine clinics and the gay community. SUBJECTS: Men (n = 677) who reported sexual contact with another man in the last 5 years. RESULTS: The majority of respondents (63%) had had an HIV-antibody test. Analysis of data showed that in 15% of the respondents' 1380 partnerships, HIV status was known by both parties. However, the majority of partnerships involved only safe sex. Only 26% of the partnerships in which unprotected penetrative anal sex had occurred involved mutual knowledge of HIV status and was most likely to occur with regular rather than non-regular/causal partners. Logistic regression revealed that this latter association could not be explained in terms of mutual HIV status knowledge. CONCLUSIONS: Despite widespread HIV testing, the majority of gay men engaging in high-risk sex are unaware of their partner's HIV status.

Adolescent↗