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Biomedical subjects

D Evans

Publications and source records attributed to D Evans.

At least 145 records · Page 8Linked to original sources
PubMed1997

Genetic diversity of Asian water buffalo (Bubalus bubalis): microsatellite variation and a comparison with protein-coding loci.

Twenty-one microsatellite loci in 11 populations of Asian water buffalo (eight swamp, three river type) were analysed and, within and among populations, genetic variability was compared with results from 25 polymorphic protein-coding loci. Within-population mean heterozygosity ranged from 0.380-0.615, approximately twice that estimated from the protein-coding loci (0.184-0.346). Only eight significant departures from Hardy-Weinberg equilibrium (involving four loci) were detected; global tests showed significant heterozygote deficiencies for these four loci. Non-amplifying alleles are likely to be segregating in some or all populations for one of these loci, and probably for the other three. There was significant differentiation between the swamp and river types of water buffalo, and among populations within each buffalo type. Estimates of theta (measure of population differentiation) for each locus for the eight swamp populations were all highly significant (mean theta = 0.168 +/- 0.018). Mean theta for protein-coding loci was not significantly different (0.182 +/- 0.041). The variance among protein-coding loci was significantly higher than among microsatellite loci, suggesting balancing selection affecting allele frequencies at some protein-coding loci. Genetic distances show clear separation of the swamp and river types, which were estimated to have diverged at least 10,000-15,000 years ago. The topology of the swamp populations' microsatellite tree is consistent with their geographical distribution and their presumed spread through south-east Asia. By contrast, the tree based on the protein-coding loci distances is quite different, being clearly distorted by a bottleneck effect in one population, and possibly in at least two others. As many domestic livestock breeds are possibly descended from small numbers of founders, microsatellite-based trees are to be preferred in assessing breed genetic relationships.

Alleles↗
PubMed1997

A scale for Assessing Health Care Providers' Teaching and Communication Behavior regarding asthma.

Partnership between health care providers and patients is important for controlling illness. A limited number of studies show how to assess health professionals' communication and partnering behavior. The relationship between these aspects of professional behavior and enhanced management of disease by patients has received little empirical study. The research reported here developed a Health Care Providers' Teaching and Communication Behavior (TCB) scale for assessing the teaching and communication behavior of clinicians treating patients with asthma. Such a tool is needed for research related to provider-patient relationships and for evaluation of professionals' performance.

Adult↗
PubMed1997

Asthma self-management programmes in a population of Italian children: a multicentric study. Italian Study Group on Asthma Self-Management Programmes.

This study was designed to answer three main questions: 1) Does asthma self-management education reduce asthma morbidity? 2) Are the two programmes "Living With Asthma" and "Open Airways" equally effective in doing so? 3) Is a shortened version of these programmes (4 weeks) as effective as the longer original programme (8 weeks)? Twelve Italian centres of paediatric bronchopneumology selected 312 children with asthma, who were stratified by disease severity, gender and age, and then randomly assigned to an Experimental group which received an educational programme or to a Comparison group, which did not. Of the 312 children selected, 209 (114 Experimental and 95 Comparison) completed the educational protocol and a 1 year follow-up. Data recorded during the last 2 months of follow-up, 10 months after the educational intervention, showed that the Experimental group required significantly fewer emergency treatments: this reduction was more evident in the more severe asthma cases. In the Experimental, but not in the Comparison group, patients with more severe asthma consumed more medications than patients with milder asthma "Open Airways" yielded, in some cases, better results than "Living with Asthma": but a type 2 error is possible. The standard and the shortened programmes proved equally effective. In conclusion, following education, regardless of receiving a short or long educational programme, asthma patients use emergency care services less and use medications more appropriately in comparison with standard care without education. This suggests that short educational programmes can be highly cost-effective in children with asthma.

Asthma↗
PubMed1997

Improving care for minority children with asthma: professional education in public health clinics.

OBJECTIVE: Recent studies have shown that lack of continuing primary care for asthma is associated with increased levels of morbidity in low-income minority children. Although effective preventive therapy is available, many African-American and Latino children receive episodic treatment for asthma that does not follow current guidelines for care. To see if access, continuity, and quality of care could be improved in pediatric clinics serving low-income children in New York City, we trained staff in New York City Bureau of Child Health clinics to provide continuing, preventive care for asthma. METHODS: We evaluated the impact of the intervention over a 2-year period in a controlled study of 22 clinics. Training for intervention clinic staff was based on National Asthma Education and Prevention Program guidelines for the diagnosis and management of asthma, and included screening to identify new cases and health education to improve family management. The intervention included strong administrative support by the Bureau of Child Health to promote staff behavior change. We hypothesized that after the intervention, clinics that received the intervention would, compared with control clinics, have increased numbers of children with asthma receiving continuing care in the clinics and increased staff use of new pharmacologic and educational treatment methods. RESULTS: In both the first and second follow-up years, the intervention clinics had greater positive changes than control clinics on measures of access, continuity, and quality of care. For second year follow-up data these include: for access, greater rate of new asthma patients (40/1000 vs 16/1000; P < .01); for continuity, greater percentage of asthma patients returning for treatment 2 years in a row (42% vs 12%; P < .001) and greater annual frequency of scheduled visits for asthma per patient (1.85 vs .88; P < .001); and for quality, greater percentage of patients receiving inhaled beta agonists (52% vs 15%; P < .001) and inhaled antiinflammatory drugs (25% vs 2%; P < .001), and greater percentages of parents who reported receiving patient education on 12 topics from Bureau of Child Health physicians (71% vs 58%; P < .01) and nurses (61% vs 44%; P < .05). CONCLUSION: We conclude that the intervention substantially increased the Bureau of Child Health staff's ability to identify children with asthma, involve them in continuing care, and provide them with state-of-the-art care for asthma.

Black or African American↗
PubMed1997

Ultrasound-based quantification of emboli during conventional and endovascular aneurysm repair.

PURPOSE: To differentiate and quantify the type and number of lower limb emboli occurring during endovascular aneurysm repair, as compared to conventional surgery. METHODS: Thirty-eight patients underwent elective infrarenal aneurysm repair using a conventional surgical approach in 18 and an endovascular procedure in 20. Emboli were detected using a Doppler ultrasound system with a 2-MHz transducer interrogating the mid superficial femoral artery. Lower limb emboli were differentiated as particulate or gaseous based on the physical distance traversed by the embolic signal. RESULTS: Significantly more particulate (median 108 versus 59, p = 0.015) and gaseous (134 versus 46, p = 0.008) emboli were detected during endovascular aneurysm repair as compared to conventional surgery. Clinically, no case of massive microembolization occurred in either group, but one patient in the conventional group required a femoral embolectomy, and three patients undergoing endovascular repair developed self-limiting trash feet postoperatively. In patients undergoing endovascular aortomonoiliac aneurysm repair, there was only a poor correlation between the number of particulate emboli and either procedural duration or operator experience. CONCLUSIONS: The apparent lack of a relationship between particulate embolization and operative time or technical experience suggests that manipulation of endoluminal devices within the aneurysm sac may not be the sole determinant of intraprocedural embolization. Other as yet undetermined factors may predict patients at high risk for massive embolization.

Aged↗
PubMed1997

Long-term results of the Angelchik prosthesis for gastro-oesophageal reflux.

INTRODUCTION: Between 1982 and 1989, 46 patients had insertion of an Angelchik prosthesis for gastro-oesophageal reflux. Eleven patients (24 per cent) subsequently had the prosthesis removed, all but one for intractable dysphagia. METHODS: Thirty-six of the original patients were followed by questionnaire, and 32 of these had a barium marshmallow swallow investigation. RESULTS: A high proportion of patients (20 of 26) with a prosthesis in situ had symptoms of dysphagia. On objective evaluation by marshmallow swallow, the transit time was significantly slower than that of an age-matched control group (P < 0.01), but showed no significant deterioration with time compared with previous postinsertion studies. CONCLUSION: The Angelchik prosthesis causes long-term dysphagia in a high proportion of patients, severe enough in one-quarter to necessitate its removal. Its continued use cannot, therefore, be recommended.

Adult↗
PubMed1997

Contrast sensitivity loss is coupled with capillary dropout in patients with diabetes.

PURPOSE: To assess the relationship of foveal microcirculation to contrast sensitivity function in early diabetes mellitus. METHODS: Twenty patients with diabetes with visual acuity of 20/25 or better without clinically significant macular edema were evaluated. Measurements of contrast sensitivity at four spatial frequencies (3, 6, 12, and 18 cycles/degree [c/deg]), macular capillary blood velocity (CBV), capillary density (PIA: perifoveal intercapillary area), foveal avascular zone (FAZ), and microaneurysm count were performed. Contrast sensitivity data collected from age-matched normal subjects and previously published normal angiographic data were used for comparison with our cohort with diabetes. RESULTS: The CBV was significantly reduced (P < 0.0001) and PIA and FAZ were significantly enlarged (P < 0.0001) when compared with healthy subjects. Contrast sensitivity was significantly lower in the group with diabetes at 6 (P = 0.01) and 12 (P = 0.002) c/deg as compared with healthy control values. FAZ and PIA correlated significantly (FAZ; r = -0.60, P = 0.005; PIA; r = -0.54, P = 0.02) with contrast sensitivity at 12 c/deg. CONCLUSIONS: The alterations of the perifoveal network are related to selective disturbances of central visual function as measured by contrast sensitivity. In patients with diabetes measurement of contrast sensitivity may provide a clinical adjunct in further identifying early ischemic diabetic maculopathy.

Adult↗
PubMed1997

Jarman underprivileged area scores, tooth decay and the effect of water fluoridation.

OBJECTIVE: To examine the association between dental caries and Jarman underprivileged area scores at regional, district and electoral ward level and explore any possible relationship with water fluoridation. DESIGN: An ecological study using the English results from the NHS dental surveys on 5-year-old children in 1991/2 and 1993/4, and the survey of 12-year-old children in 1992/3. Jarman underprivileged area scores were used from the 1991 census. SETTING: The study used former English health authority regions and districts. The electoral wards were in non-fluoridated Salford and Trafford and Liverpool, and fluoridated Newcastle and North Tyneside. SUBJECTS: The random sample of 5-year-old children examined in 1991/2 and 1993/4, and 12-year-old children in 1992/3, in studies coordinated by the British Association for the Study of Community Dentistry. OUTCOME MEASURES: Correlations between regional, district and electoral ward mean dmft/DMFT and Jarman underprivileged area scores. RESULTS: Significant correlations were demonstrated at a regional level in 5-year-old children in 1991/2, district level in 5-year-old children in 1991/2 and 1993/4 and at electoral ward level in both age groups in 1992/3 and 1993/4. Correlation coefficients varied between r = 0.88 to r = 0.46. Multiple linear regression at electoral ward level showed significant interactions between Jarman scores and water fluoridation. There was an average 44 per cent and 43 per cent reduction in caries in fluoridated electoral wards in 5- and 12-year-old children respectively. In deprived electoral wards, with a Jarman score of 40, the reduction in caries increased to 54 per cent and 56 per cent for 5- and 12-year-old children respectively. CONCLUSIONS: Dental caries was associated with Jarman underprivileged area scores. The differential efficacy of fluoridation to deprived areas was demonstrated at electoral ward level. Water fluoridation was confirmed as an evidence based intervention which has halved the amount of tooth decay in 5- and 12-year-old children.

Child↗
PubMed1996

Identification and eradication of a denatured DNA isolated during alkaline lysis-based plasmid purification procedures.

Many plasmid isolation procedures use strongly alkaline conditions in the initial stages to facilitate lysis of the host bacteria. We demonstrate that such procedures can give rise to a minor but significantly altered form of plasmid. After electrophoresis and uv transillumination of ethidium bromide-stained agarose gels we and others have noticed a faint band migrating near to the major fluorescent product, covalently closed circular plasmid DNA. This faint band is resistant to cleavage by restriction endonucleases which have recognition sites in the parent plasmid. We were able to show that the contaminating band is able to transform competent Escherichia coli cells and that normal double-stranded plasmids were isolated from such transformants. We were able to selectively hydrolyze the contaminating band using T5 exonuclease which is a 5'-nuclease with a single-strand specific endonuclease activity. Plasmid preparations carried out under nonalkaline conditions failed to produce the contaminant band. We suggest methods for purifying plasmid DNA which remove the denatured band and could improve cloning efficiencies where the largest recombinant libraries are required.

DNA, Recombinant↗
PubMed1996

Optimal filtering of EIT data in spectral expansion analysis.

The signal-to-noise rations for some EIT measurements are very low, and for in vivo EIT measurements these are dependent on the electrode positioning and the distance from the current drive. The effect of removing noisy measurements to produce higher-fidelity images was investigated for the case of gastric emptying data. A consequence of this filtering was the reduction in the size of the sensitivity matrix and its subsequent singular-value decomposition. Several different filters were tested and for each of these spectral expansion regularization filter was optimized using a chi 2 test. Filtering out the measurement made by the spinal electrode, where the spinal bone barrier lies directly in the current path to the stomach, produced improved images by reducing the artefact content in the spinal sector of the conductivity map. For stomach imaging little useful information is produced by the spinal electrode, and the benefits of filtering dominate. However artefact images may be generated. In contrast consistent small improvements were produced by filtering out some of the weakest signals.

Data Interpretation, Statistical↗
PubMed1996

Acute IOP elevation with scleral suction: effects on retrobulbar haemodynamics.

AIMS/BACKGROUND: Mechanical and vascular factors may both contribute to glaucoma. This study investigated the relation of mechanical to vascular factors by examining how acute IOP elevation altered flow velocities in the central retinal and ophthalmic arteries. METHODS: IOP was elevated from a baseline near 14 to approximately 45 mm Hg using suction ophthalmodynamometry. During recovery from scleral suction, IOP fell to near 8 mm Hg. At each IOP, peak systolic and end diastolic velocities (PSV and EDV) were measured in the central retinal and ophthalmic arteries using colour Doppler imaging (Siemens Quantum 2000). Eleven healthy people served as subjects. RESULTS: Acute elevation in IOP had no effect upon PSV, EDV, or the derived resistance index in the ophthalmic artery: flow velocities in this vessel were identical at IOP of 8 mm Hg or 45 mm Hg. In contrast, in the central retinal artery, PSV and EDV fell, and the resistance index rose, in steady progression as IOP was acutely elevated (each p < 0.01). At IOP of 45 mm Hg, EDV was virtually absent and the resistance index was very nearly 1.0. CONCLUSION: Ophthalmic arterial haemodynamics are unrelated to acute fluctuations of the IOP over a wide range, suggesting that ocular hypertension itself cannot induce vascular dysfunction in this artery. In contrast, flow velocities in the central retinal artery were highly IOP dependent, implying that haemodynamic and mechanical factors are closely linked in this vascular bed.

Acute Disease↗
PubMed1996

Hyperoxia improves contrast sensitivity in early diabetic retinopathy.

AIM: The cause of vascular and visual pathology in diabetic retinopathy remains unknown. If retinal hypoxia plays a role, then early in the course of diabetes 100% oxygen breathing should normalise both contrast sensitivity and retinal blood flow. METHODS: This hypothesis was tested in 12 diabetic patients with minimal retinopathy who, none the less, exhibited reduced contrast sensitivity (p = 0.003 versus 12 age and sex-matched controls) and prolonged retinal arteriovenous dye transit (p = 0.0001 versus controls). RESULTS: Isocapnic hyperoxia failed to alter contrast sensitivity in controls, while it significantly improved contrast sensitivity in patients (at 12 cpd; p = 0.042) to levels indistinguishable from normal. Individual improvement in contrast sensitivity correlated positively with the severity of the initial defect (r = +0.84, p = 0.0008). Hyperoxia also had haemodynamic effects; it slowed retinal arteriovenous passage of fluorescein dye in controls, but did not further slow this transit time in patients. CONCLUSIONS: These results demonstrate the reversibility of early contrast sensitivity deficits in diabetes mellitus, and support the hypothesis that factors linked to tissue hypoxia initiate both visual and vascular dysfunction in diabetic retinopathy.

Adult↗
PubMed1996

An interview based approach to seeking user views in genitourinary medicine.

OBJECTIVES: To assess user and potential user views on the appropriateness, nature and quality of genitourinary medicine (GUM) provision in Bristol, UK and to develop a model for ongoing user consultation by GUM providers and purchasers. DESIGN: This qualitative study was based on semi-structured interviews with service users, potential users, community informants and NHS professionals. PARTICIPANTS: 76 current, past or potential users, 10 community informants and 11 NHS professionals were interviewed. African-Caribbean women and men, homeless men and women, lesbians and gay men, men and women living with HIV and women working in the sex industry were recruited to maximise the diversity of the sample. RESULTS: The interviews demonstrated that participants commented positively on many aspects of the service available. The research also identified a number of areas where the service could be improved. Many users emphasised their initial difficulty in finding out about the department and the need for greater publicity and outreach. Users reported coming to the clinic with high levels of anxiety and negative preconceptions about the GUM service. Specific issues were identified for different groups of users. There was a strongly expressed need from a number of women and African-Caribbean men for completely single sex clinics. CONCLUSIONS: The research identified a number of issues of importance to service users that had not been identified in the department's own questionnaire surveys. The results support the premise that qualitative interviews can be successfully employed to access a diverse sample of users, and can offer insights significantly beyond those available from structured patient questionnaires.

Appointments and Schedules↗
PubMed1996

Ocular hemodynamic effects of acute ethanol ingestion.

PURPOSE: Because the protean biological effects of ethanol include acute alterations in both cortical function and circulatory control, we investigated the effect of acute alcohol consumption on retrobulbar hemodynamics and contrast sensitivity in healthy human volunteers. SUBJECTS AND METHODS: Twelve young adults received orange juice with and without ethanol in a double-masked fashion. The ethanol dose was sufficient to raise blood alcohol to 0.07 +/- 0.003 g/dl. Retrobulbar hemodynamics were assessed at baseline and twice at elevated blood alcohol by color Doppler imaging. RESULTS: Acute elevation of blood alcohol lowered intraocular pressure from 13.0 +/- 0.7 to 10.7 +/- 0.7 mm Hg (p < 0.05). In contrast, elevated blood alcohol left peak systolic velocity, end-diastolic velocity and the resistance index constant in three retrobulbar arteries (ophthalmic, central retinal and posterior ciliary). For example, in the central retinal artery, peak systolic velocity, end-diastolic velocity and the resistance index averaged 11.0 +/- 1.3 cm/s, 2.8 +/- 0.4 cm/s and 0.75 +/- 0.03 before ethanol, as compared with 10.5 +/- 1.0 cm/s, 2.9 +/- 0.3 cm/s and 0.72 +/- 0.03 after ethanol (all p = NS). Alcohol ingestion also failed to alter either visual acuity or contrast sensitivity, as assessed under both photopic and mesopic conditions. CONCLUSIONS: Although ethanol has widespread cognitive and cardiovascular effects, at blood levels near legal definitions of intoxication we found it ineffective in altering either retrobulbar hemodynamics or contrast sensitivity.

Adult↗
PubMed1996

Increased exhaled nitric oxide in asthma is mainly derived from the lower respiratory tract.

Nitric oxide (NO) is detectable in the exhaled air of human subjects, and its concentration is increased in patients with asthma. We have investigated the origin of the increase in exhaled NO in asthmatic patients by using different expiratory maneuvers and by direct sampling from the upper and lower respiratory tracts. Exhaled NO was measured by a chemiluminescence analyzer. Concentrations of NO measured during expiration against the resistance of the analyzer with exhaled flow of 1 L/min, were 78 +/- 3 ppb in normal subjects (n = 46) and significantly elevated in patients with asthma (301 +/- 26 ppb, n = 30, p < 0.001). Values of exhaled NO were lower when measured during unobstructed expiration with a flow of 5 L/min with sampling from a side-arm (7 +/- 1 ppb), but again were elevated in patients with asthma (46 +/- 6 ppb, p < 0.001). Breath-holding for 20 s resulted in an initial peak of NO, but end-expiration values similar to the unobstructed expiration. The concentration of NO in the nose was considerably greater than in expired air (996 +/- 39 ppb) and was elevated in patients with asthma (1,390 +/- 71 ppb, p < 0.002). Direct sampling from trachea and right middle lobe bronchus via a fiberoptic bronchoscope gave similar values in five normal and 15 asthmatic subjects to the values recorded during unobstructed expiration, and there was a good correlation between values in expired air and direct sampling (trachea r = 0.91, right middle lobe r = 0.87, p < 0.001). We conclude that exhaled NO measured in an unobstructed breath reflects concentrations in the lower respiratory tract, but that breath-holding or expiration against resistance is contaminated by residual NO derived from the upper respiratory tract. We also provide evidence that the elevated levels of exhaled NO in asthmatic patients are derived predominantly from the lower respiratory tract.

Adult↗