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Biomedical subjects

R H Baker

Publications and source records attributed to R H Baker.

At least 19 recordsLinked to original sources
PubMed2003

Are audits wasting resources by measuring the wrong things? A survey of methods used to select audit review criteria.

OBJECTIVES: This study measured the extent to which a systematic approach was used to select criteria for audit, and identified problems in using such an approach with potential solutions. DESIGN: A questionnaire survey using the Audit Criteria Questionnaire (ACQ), created, piloted, and validated for the purpose. Possible ACQ scores ranged from 0 to 1, indicating how systematically the criteria had been selected and how usable they were. SETTING: A stratified random sample of 10 audit leads in each of 83 randomly selected NHS trusts and all practices in each of 11 randomly selected primary care audit group areas in England and Wales. PARTICIPANTS: Audit leads of ongoing audits in each organisation in which a first data collection had started less than 12 months earlier and a second data collection was not completed. MAIN OUTCOME MEASURES: ACQ scores, problems identified in the audit criteria selection process, and solutions found. RESULTS: The mean ACQ score from all 83 NHS trusts and the 11 primary care audit groups was 0.52 (range 0.0-0.98). There was no difference between mean ACQ scores for criteria used in audits on clinical (0.51) and non-clinical (0.52) topics. The mean ACQ scores from nationally organised audits (0.59, n=33) was higher than for regional (0.51, n=21), local (0.53, n=77), or individual organisation (0.52, n=335) audits. The mean ACQ score for published audit protocols (0.56) was higher than for locally developed audits (0.49). There was no difference in ACQ scores for audits reported by general practices (0.49, n=83) or NHS trusts (0.53, n=383). Problems in criteria selection included difficulties in coordination of staff to undertake the task, lack of evidence, poor access to literature, poor access to high quality data, lack of time, and lack of motivation. Potential solutions include investment in training, protected time, improved access to literature, support staff and availability of published protocols. CONCLUSIONS: Methods of selecting review criteria were often less systematic than is desirable. Published usable audit protocols providing evidence based review criteria with information on their provenance enable appropriate review criteria to be selected, so that changes in practice based on these criteria lead to real improvement in quality rather than merely change. The availability and use of high quality audit protocols would be a valuable contribution to the evolution of clinical governance. The ACQ should be developed into a tool to help in selecting appropriate criteria to increase the effectiveness of audit.

England↗
PubMed2001

Polytene chromosomes as indicators of phylogeny in several species groups of Drosophila.

BACKGROUND: Polytene chromosome banding patterns have long been used by Drosophila evolutionists to infer degree of relatedness among taxa. Recently, nucleotide sequences have preempted this traditional method. We place the classical Drosophila evolutionary biology tools of polytene chromosome inversion analysis in a phylogenetic context and assess their utility in comparison to nucleotide sequences. RESULTS: A simultaneous analysis framework was used to examine the congruence of the chromosomal inversion data with more recent DNA sequence data in four Drosophila species groups - the melanogaster, virilis, repleta, and picture wing. Inversions and nucleotides were highly congruent with one another based on incongruence length difference and partitioned Bremer support values. Inversion phylogenies were less resolved because of fewer numbers of characters. Partitioned Bremer supports, corrected for the number of characters in each matrix, were higher for inversion matrices. CONCLUSIONS: Polytene chromosome data are highly congruent with DNA sequence data and, when placed in a simultaneous analysis framework, are shown to be more information rich than nucleotide data.

Animals↗
PubMed2001

Phylogenetic analysis of sexual dimorphism and eye-span allometry in stalk-eyed flies (Diopsidae).

Eye stalks and their scaling relationship with body size are important features in the mating system of many diopsid species, and sexual selection is a critical force influencing the evolution of this exaggerated morphology. Interspecific variation in eye span suggests there has been significant evolutionary change in this trait, but a robust phylogenetic hypothesis is required to determine its rate and direction of change. In this study, the pattern of morphological evolution of eye span is assessed in a phylogenetic framework with respect to its function in the sexual system of these flies. Specifically, we examine within the family Diopsidae the pattern of increase and decrease in sexual dimorphism, the morphological coevolution of eye span between males and females, and the evolutionary flexibility of eye-span allometry. Based on several different methods for reconstructing morphological change, results suggest a general pattern of evolutionary flexibility, particularly for eye-span allometry. Sexual dimorphism in eye span has evolved independently at least four times in the family and this trait also has undergone several reductions within the genus Diasemopsis. Despite most species being dimorphic, there is a strong phylogenetic correlation between males and females for mean eye span. The coevolution between the sexes for eye-span allometry, however, is significantly weaker. Overall, eye-span allometry exhibits significantly more change on the phylogeny than the other morphological traits. The evolutionary pattern in eye-span allometry is caused primarily by changes in eye-span variance. Therefore, this pattern is consistent with recent models that predict a strong relationship between sexual selection and the variance of ornamental traits and highlights the significance of eye-span allometry in intersexual and intrasexual signaling.

Animals↗
PubMed2001

Expert consensus on the desirable characteristics of review criteria for improvement of health care quality.

OBJECTIVES: To identify the desirable characteristics of review criteria for quality improvement and to determine how they should be selected. BACKGROUND: Review criteria are the elements against which quality of care is assessed in quality improvement. Use of inappropriate criteria may impair the effectiveness of quality improvement activities and resources may be wasted in activities that fail to facilitate improved care. METHODS: A two round modified Delphi process was used to generate consensus amongst an international panel of 38 experts. A list of 40 characteristics of review criteria, identified from literature searches, was distributed to the experts who were asked to rate the importance and feasibility of each characteristic. Comments and suggestions for characteristics not included in the list were also invited. RESULTS: The Delphi process refined a comprehensive literature based list of 40 desirable characteristics of review criteria into a more precise list of 26 items. The expert consensus view is that review criteria should be developed through a well documented process involving consideration of valid research evidence, possibly combined with expert opinion, prioritisation according to health outcomes and strength of evidence, and pilot testing. Review criteria should also be accompanied by full clear information on how they might be used and how data might be collected and interpreted. CONCLUSION: The desirable characteristics for review criteria have been identified and will be of use in the development, evaluation, and selection of review criteria, thus improving the cost effectiveness of quality improvement activities in healthcare settings.

Consensus Statements as Topic↗
PubMed2001

Phylogenetic utility of different types of molecular data used to infer evolutionary relationships among stalk-eyed flies (Diopsidae).

A phylogenetic hypothesis of relationships among 33 species of stalk-eyed flies was generated from a molecular data set comprising three mitochondrial and three nuclear gene regions. A combined analysis of all the data equally weighted produced a single most-parsimonious cladogram with relatively strong support at the majority of nodes. The phylogenetic utility of different classes of molecular data was also examined. In particular, using a number of different measures of utility in both a combined and separate analysis framework, we focused on the distinction between mitochondrial and nuclear genes and between faster-evolving characters and slower-evolving characters. For the first comparison, by nearly any measure of utility, the nuclear genes are substantially more informative for resolving diopsid relationships than are the mitochondrial genes. The nuclear genes exhibit less homoplasy, are less incongruent with one another and with the combined data, and contribute more support to the combined analysis topology than do the mitochondrial genes. Results from the second comparison, however, provide little evidence of a clear difference in utility. Despite indications of rapid divergence and saturation, faster-evolving characters in both the nuclear and mitochondrial data sets still provide substantial phylogenetic signal. In general, inclusion of the more rapidly evolving data consistently improves the congruence among partitions.

ATP-Binding Cassette Transporters↗
PubMed2000

Phylogenetic analysis of the repleta species group of the genus Drosophila using multiple sources of characters.

The species in the repleta group of the genus Drosophila have been placed into five subgroups-the mulleri, hydei, mercatorum, repleta, and fasciola subgroups. Each subgroup has been further subdivided into complexes and clusters. Extensive morphological and cytological analyses of the members of this species group have formed the foundation for the proposed relationships among the members of the repleta species group. Fifty-four taxa, including 46 taxa belonging to the repleta species group, were sequenced for fragments of four genes-16S ribosomal DNA (16S), cytochrome oxidase II (COII), and nitrogen dehydrogenase 1 (ND1) of the mitochondrial genome and a region of the hunchback (hb) nuclear gene. We also generated a partial data set of elongation factor 1-alpha (Ef1alpha) sequences for a subset of taxa. Our analysis used both DNA characters and chromosomal inversion data. The phylogenetic hypothesis we obtained supports many of the traditionally accepted clades within the mulleri subgroup, but the monophyly of taxonomic groups outside of this subgroup appears not to be supported. Phylogenetic analysis revealed one well-supported, highly resolved clade that consists of closely related members of the mulleri and buzzatii complexes. The remaining taxa, a wide assortment of taxonomic groups, ranging from members of other species groups to members of several subgroups and members of three species complexes from the mulleri subgroup are found in poorly supported arrangements at the base of the tree.

Animals↗
PubMed1998

Assessing the relative contribution of molecular and morphological characters in simultaneous analysis trees.

We examined the contribution of morphological and molecular character information for 15 systematics studies in which these two kinds of data were used in combined or simultaneous analyses. Assessment of the disagreement between these data sources, as measured by the incongruence length difference, reveals substantial conflict for the studies surveyed. In addition, the partitioned Bremer support was used to measure the degree of support provided by each data partition when analyzed together. Despite the significant incongruence found for nearly half the studies, the PBS indices suggest both types of data contribute positively to the combined analyses and that, when standardized by the number of phylogenetically informative characters, morphology data generally provide equal or greater support than do the molecular data. This result, combined with the fact that morphological characters generally exhibit higher consistency, indicates that this source of character information continues to be useful in systematics studies despite the increasing volume of available molecular data.

Animals↗
PubMed1997

Multiple sources of character information and the phylogeny of Hawaiian drosophilids.

Relationships among representatives of the five major Hawaiian Drosophila species groups were examined using data from eight different gene regions. A simultaneous analysis of these data resulted in a single most-parsimonious tree that (1) places the adiastola picture-winged subgroup as sister taxon to the other picture-winged subgroups, (2) unites the modified-tarsus species group with flies from the Antopocerus species group, and (3) places the white-tip scutellum species group as the most basal taxon. Because of the different gene sources used in this study, numerous process partitions can be erected within this data set. We examined the incongruence among these various partitions and the ramifications of these data for the taxonomic consensus, prior agreement, and simultaneous analysis approaches to phylogenetic reconstruction. Separate analyses and taxonomic consensus appear to be inadequate methods for dealing with the partitions in this study. Although detection of incongruence is possible and helps elucidate particular areas of disagreement among data sets, separation of partitions on the basis of incongruence is problematic for many reasons. First, analyzing all genes separately and then either presenting them all as possible hypotheses or taking their consensus provides virtually no information concerning the relationships among these flies. Second, despite some evidence of incongruence, there are no clear delineations among the various gene partitions that separate only heterogeneous data. Third, to the extent that problematic genes can be identified, these genes have nearly the same information content, within a combined analysis framework, as the remaining nonproblematic genes. Our data suggest that significant incongruence among data partitions may be isolated to specific relationships and the "false" signal creating this incongruence is most likely to be overcome by a simultaneous analysis. We present a new method, partitioned Bremer support, for examining the contribution of a particular data partition to the topological support of the simultaneous analysis tree.

Animals↗
PubMed1997

Studies on a primaquine-tolerant strain of Plasmodium vivax from Brazil in Aotus and Saimiri monkeys.

A nonimmune American acquired an infection of Plasmodium vivax Type 1 malaria in Brazil in 1994. After returning to the U.S.A., he had a primary attack followed by 3 relapses. The primary attack and first 2 relapses were treated with a standard regimen of chloroquine, followed by 14 days of primaquine (15 mg/day). Following the third relapse, the primaquine treatment was extended to 28 days. No further relapses occurred. The lack of response to primaquine by this strain may recommend it as a suitable candidate for chemotherapeutic study if it can be adapted to an animal model. Anopheles quadrimaculatus mosquitoes infected by feeding on the patient during the first relapse were used to establish the strain in Aotus and Saimiri monkeys. Monkeys supported well the development of long-lasting parasitemia. Anopheles freeborni, Anopheles stephensi, and Anopheles gambiae mosquitoes were readily infected by feeding on the monkeys and by membrane feeding on diluted blood. Monkey-to-monkey transmission was obtained via the bites of infected mosquitoes and the intravenous injection of sporozoites dissected from salivary glands. This parasite is designated as the Brazil I/CDC strain of P. vivax.

Animals↗
PubMed1995

Confounders of auscultatory blood pressure measurement.

The appropriate use of any test requires the clinician to appreciate that test's limitations. By recognizing the potential confounders of the auscultatory assessment of blood pressure, the clinician minimizes the likelihood of enacting therapeutic decisions based on inaccurate data. When approaching the treatment of a hypertensive patient, several points should be kept in mind. First, the measurement of persistent and severe hypertension in a patient receiving treatment who describes symptoms of orthostatic hypotension with apparently adequate standing blood pressure or who lacks corroborating retinal, echocardiographic, or electrocardiographic signs of hypertension should raise the concern of pseudohypertension or a white-coat response. Similarly, when one finds a normal or near-normal systolic blood pressure in a patient with a clinical picture consistent with severe hypertension, one should make a directed effort to look for an unrecognized auscultatory gap. Second, marked discrepancies in measurements as obtained by different operators or in different settings should raise concern of the white-coat response or methodologic errors by one operator, such as undercuffing, excessive pressure on the head of the stethoscope, rapid deflation of the cuff, or use of different arms. In treating hypertension in even the minimally obese patient, a special point must be made that an adequate size cuff be used for all blood pressure determinations. Third, when blood pressure is determined with the patient in any but the satndardized back-and-arm-supported seated position described above, the clinician should acknowledge the possibility that the position may alter the patient's classification. Fourth, the diagnosis and management of hypertension requires multiple measurements of blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Auscultation↗
PubMed1992

Aqueous dynamics in exfoliation syndrome.

Eighteen untreated patients with unilateral exfoliation syndrome without glaucoma were studied with regard to differences in aqueous dynamics between the affected and unaffected fellow eyes. Additionally, both eyes of the patients with exfoliation were compared to the eyes of 18 age-matched and gender-matched control subjects. Intraocular pressure was significantly higher (13.9 +/- 3.0 mm Hg [mean +/- standard deviation]) in the affected compared with the unaffected eyes (12.2 +/- 2.5 mm Hg), but no difference in aqueous humor flow was detected when eyes in the three groups were compared (affected eyes, 2.40 +/- 0.60 microliter/min; unaffected eyes, 2.40 +/- 0.65 microliter/min; control eyes, 2.61 +/- 0.60 microliter/min). Anterior chamber volumes were significantly smaller in affected (122 +/- 37 microliters) and unaffected eyes (121 +/- 37 microliters) of the patients with exfoliation compared with the eyes of the control subjects (145 +/- 30 microliters). Apparent resistance was higher in the eyes with exfoliation (6.5 +/- 1.9 min mm Hg/microliters) compared with both unaffected (5.4 +/- 1.2 min mm Hg/microliters) and control groups (5.2 +/- 1.8 min mm Hg/microliters), although these differences were not statistically significant.

Aged↗
PubMed1991

Familial polyposis coli: the spectrum of ocular and other extracolonic manifestations.

Familial polyposis coli (FPC) is hereditary condition that conveys a virtual 100% risk for the development of colon cancer in the untreated patient. A total of 56 patients with FPC underwent complete ophthalmic examination. Highly pleomorphic pigmented retinal lesions were identified bilaterally in 52% (n = 29) and unilaterally in 14% (n = 8) of our subjects. In all, 33 patients had one or more extracolonic expressions associated with FPC, including desmoids, osteomas, epidermoid cysts, lipomas, fibromas, and upper gastrointestinal tract polyps. In 15 patients, pigmented fundus lesions were the only extracolonic manifestations. No significant association between eye findings and other extracolonic manifestations could be established. The presence or absence of pigmented fundus lesions was found to cluster within families. Pigmented fundus lesions are probably a variably penetrant expression of the polyposis gene and do not appear to be specifically associated with subgroups of inherited polyposis syndromes such as Gardner's syndrome.

Adenomatous Polyposis Coli↗
PubMed1991

Extracellular deposition of eosinophil major basic protein in orbital histiocytosis X.

Although eosinophils are prominent in orbital lesions of patients with histiocytosis X (Langerhans' cell histiocytosis), little is known of their pathogenic significance in the disease. To determine whether eosinophils degranulate and deposit toxic proteins in orbital histiocytosis X, the authors examined lesions by indirect immunofluorescence for localization of the core granule protein (major basic protein) outside of eosinophils. Four patients with histiocytosis X were studied: three with eosinophilic granuloma and one with Hand-Schüller-Christian disease. Tissue eosinophilia was prominent in all specimens; striking extracellular deposition of eosinophil major basic protein was noted in three patients, and focal deposition was present in the fourth patient. Orbital specimens obtained at autopsy from patients without orbital disease were studied as control specimens; no tissue eosinophilia or deposition of eosinophil major basic protein was observed. These findings indicate that eosinophils likely degranulate in lesions of orbital histiocytosis X and may participate in the pathogenesis of the disease.

Adolescent↗
PubMed1990

Progress in controlling the reinvasion of windborne vectors into the western area of the Onchocerciasis Control Programme in West Africa.

Since vector control began in 1975, waves of Simulium sirbanum and S. damnosum s.str., the principal vectors of severe blinding onchocerciasis in the West African savannas, have reinvaded treated rivers inside the original boundaries of the Onchocerciasis Control Programme in West Africa. Larviciding of potential source breeding sites has shown that these 'savanna' species are capable of travelling and carrying Onchocerca infection for at least 500 km northeastwards with the monsoon winds in the early rainy season. Vector control has, therefore, been extended progressively westwards. In 1984 the Programme embarked on a major western extension into Guinea, Sierra Leone, western Mali, Senegal and Guinea-Bissau. The transmission resulting from the reinvasion of northern Côte d'Ivoire and Burkina Faso has been reduced by over 95%, but eastern Mali has proved more difficult to protect because of sources in both Guinea and Sierra Leone. Rivers in Sierra Leone were treated for the first time in 1989 and biting and transmission rates in Sierra Leone and Guinea fell by over 90%. Because of treatment problems in some complex rapids and mountainous areas, flies still reinvaded Mali, though biting rates were approximately 70% lower than those recorded before anti-reinvasion treatments started. It was concluded that transmission in eastern Mali has now been reduced to the levels required to control onchocerciasis.

Africa, Western↗