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Biomedical subjects

L Walker

Publications and source records attributed to L Walker.

At least 37 records · Page 2Linked to original sources
PubMed2001

High-resolution magic angle spinning 1H-NMR spectroscopy studies on the renal biochemistry in the bank vole (Clethrionomys glareolus) and the effects of arsenic (As3+) toxicity.

1. High-resolution magic angle spinning (MAS) 1H-NMR spectroscopy was used to study renal metabolism and the toxicity of As3+, a common environmental contaminant, in the bank vole (Clethrionomys glareolus), a wild species of rodent. 2. Following a 14-day exposure to an environmentally relevant dose of As2O3 (28 mg kg(-1) feed), voles displayed tissue damage at autopsy. MAS 1H spectra indicated abnormal lipid profiles in these samples. 3. Tissue necrosis was also evident from measurements of the apparent diffusion coefficient of water in the intact tissue using MAS 1H diffusion-weighted spectroscopy, its first application to toxicology. 4. Comparison of renal tissue from the wood mouse (Apodemus sylvaticus) exposed to identical exposure levels of As3+ suggested that the bank vole is particularly vulnerable to As3+ toxicity.

Alanine↗
PubMed2001

Detection of severe nondeletional alpha-thalassemia mutations using a single-tube multiplex ARMS assay.

Alpha-thalassemia is a common hereditary anemia due to decreased or absent synthesis of alpha-globin chains. The most common causes of alpha-thalassemia are deletions that remove one or both functional alpha-globin genes, with a small proportion of cases involving nondeletional mutations of the alpha2- or alpha1-globin genes. Herein, we describe a single-tube multiplex amplification refractory mutation system (ARMS) assay for rapid detection of six of the most common and severe nondeletional alpha-thalassemia mutations. These alleles are found predominantly among southeast Asian populations, and are associated with the most severe forms of hemoglobin (Hb) H disease or Hb H hydrops fetalis.

Globins↗
PubMed2001

'Conservative pioneers': the formation of the South African Society of Medical Women.

This article analyses the professional struggles for the South African Society of Medical Women during the 1950s and 1960s. Drawing on interview and archival material, it details their first two campaigns. The first aimed to raise the retirement age of women doctors to bring it in line with their male colleagues, and the second sought to abolish the marriage bar which prevented married women from working in the public service. The research revealed them to have been successful in their endeavours. The article argues that their success was largely due to their conservative gender and racial ideology. The Society sought inclusion into the profession in ways which suited the interests of both men and the state. They widened women's access to the profession without upsetting the gender hierarchies of the medical profession. While their conservative 'gender' strategies facilitated their professional inclusion, so too did their race. This article argues that their whiteness ensured that they were the beneficiaries of racial inclusion in a profession structured by racist conventions and divided along racial lines.

History, 20th Century↗
PubMed2001

Evaluation of cross-sectional luminal morphology in carotid atherosclerotic disease by use of spiral CT angiography.

BACKGROUND AND PURPOSE: This study sought to determine the frequency of noncircular lumens in patients with significant carotid atherosclerotic disease and to evaluate the effect of noncircular lumens on stenosis measurement derived from angiographic projections. METHODS: One hundred consecutive patients presenting with an internal carotid artery stenosis of at least 50% were imaged with spiral CT angiography. The transverse morphology of the diseased lumen was assessed on axial images, and the frequency of noncircular lumens was determined. In these cases, maximum intensity projection angiograms were reconstructed in standardized angiographic planes and in a plane selected according to the luminal obliquity, which was chosen to optimize the angiographic representation of the maximal stenosis. North American Symptomatic Carotid Endarterectomy Trial (NASCET) measurements were calculated from the maximum intensity projection images, and differences between values obtained from standard and optimized projections were recorded. RESULTS: Noncircular lumens were observed in 18 of 100 patients and consisted of elliptical and linear transverse profiles. The transverse orientation of the lumen in these cases ranged from +90 degrees to -87 degrees relative to the anteroposterior plane. An increase in the calculated NASCET stenosis was demonstrated when measurements were obtained from angiographic reconstructions obtained in the exact plane of the luminal obliquity compared with standard angiographic projections. As a result, the stenosis severity was upgraded from moderate to severe in 2 patients. CONCLUSIONS: Noncircular transverse luminal profiles are not uncommon and may introduce error into NASCET calculations obtained from standard angiographic projections.

Anatomy, Cross-Sectional↗
PubMed2001

Evidence that systemic gentamicin suppresses premature stop mutations in patients with cystic fibrosis.

Here we report the effects of gentamicin treatment on cystic fibrosis transmembrane regulator (CFTR) production and function in CF airway cells and patients with CF with premature stop mutations. Using immunocytochemical and functional [6-methoxy-N- (3-sulfopropyl) quinolinium (SPQ)-based] techniques, ex vivo exposure of airway cells from stop mutation CF patients led to the identification of surface-localized CFTR in a dose-dependent fashion. Next, five patients with CF with stop mutations and five CF control subjects were treated with parenteral gentamicin for 1 wk, and underwent repeated in vivo measures of CFTR function (nasal potential difference [PD] measurements and sweat chloride [Cl(-)] testing). During the treatment period, the number of nasal PD readings in the direction of Cl(-) secretion was increased approximately 3-fold in the stop mutation patient group compared with controls (p < 0.001), and four of five stop mutation patients with CF had at least one reading during gentamicin treatment with a Cl(-) secretory response of more than -5 mV (hyperpolarized). A response of this magnitude was not seen in any of the CF control subjects (p < 0.05). In an independent series of experiments designed to test the ability of repeat nasal PDs to detect wild-type CFTR function, evidence of Cl(-) secretion was seen in 88% of control (non-CF) nasal PDs, and 71% were more than -5 mV hyperpolarized. Together, these results suggest that gentamicin treatment can suppress premature stop mutations in airway cells from patients with CF, and produce small increases in CFTR Cl(-) conductance (as measured by the nasal PD) in vivo.

Adolescent↗
PubMed2001

Obesity.

Explore the source record for details and available documents.

Adipose Tissue↗
PubMed2001

The notch receptor and its ligands are selectively expressed during hematopoietic development in the mouse.

Members of the Notch family of transmembrane receptors are found on primitive hematopoietic precursors, and Notch ligand expression has been demonstrated on the surface of stromal cells, suggesting a role for Notch signaling in mammalian blood cell development. The current report examines the expression of Notch receptors and their ligands in murine hematopoietic tissues to determine: A) which blood cell lineages in the adult are influenced by Notch activity, and B) whether fetal hematopoiesis in the embryo involves the Notch pathway. In the adult mouse, a combination of flow cytometry, immunohistochemistry and Northern analysis was used to examine Notch receptor or ligand expression in bone marrow and spleen. In the embryo, Northern analysis and in situ hybridization were used to characterize Notch receptor and ligand expression in fetal liver on embryonic day 12 (E12) through E17, an active period encompassing both erythropoiesis and granulopoeisis. Flow cytometry demonstrated the presence of Notch1 and Notch2 receptors on bone marrow-derived myeloid cells but not on erythroid cells positive for the marker, Ter-119. In situ hybridization of E12 through E17 fetal liver demonstrated widespread expression of Jagged1 and Delta1 in a pattern similar to but less abundant than that of the erythropoietin receptor. Taken together with earlier functional results, the current expression data suggest a role for Notch activity in establishing definitive hematopoiesis in fetal liver, as well as a selective use of Notch signaling in adult erythropoiesis and granulopoiesis. Notch receptors in the adult are most likely utilized by early erythroid precursors and intermediate-stage granulocytes, but not by terminally differentiating cells of either subset.

Animals↗
PubMed2001

Some issues relevant to establishing a universal newborn hearing screening program.

This article describes some of the factors relevant to the establishment of a universal newborn hearing screening (UNHS) program. First, the difficulty in providing precise estimates of test sensitivity and specificity are reviewed. This section is followed by hypothetical estimates of overall programmatic costs, first for a fixed number of babies to be screened and then as a function of the number of babies to be screened in a year. Included in these estimates are the costs for equipment, disposables, personnel, and follow-up testing. These estimates are provided for three different screening protocols: auditory brainstem response (ABR) alone, otoacoustic emission (OAE) alone, and OAE followed by ABR only for those babies who failed the OAE screening. If follow-up costs are not included, it is less expensive to screen newborns with OAEs compared with the other two protocols. However, once follow-up testing is included as part of the program costs and there are at least 400 births per year, procedures in which OAEs are performed first, followed by an ABR on those infants who do not pass the OAE test, result in the lowest costs. Hospitals with as few as 400 births per year should expect per-baby costs not exceeding $30, regardless of which protocol is used. For all three protocols, the unit costs decrease as the number of babies screened increases. The final section describes data from a local UNHS program in which all infants are screened first with an OAE test, followed by an ABR test on infants not passing the OAE screening. Idiosyncratic features to this program are described, including the fact that all screening tests are performed by audiologists, who are paid on a part-time basis, adding cost to the program. Even under these circumstances, the unit cost is under $30. These data lead us to conclude that all infants can be screened in a cost-effective manner.

Cost-Benefit Analysis↗
PubMed2001

An improved method for the determination of betaine in Echinacea products.

A rapid and sensitive HPLC method for the separation and quantification of betaine in Echinacea products has been developed. Strong cation-exchange (SCX) material was used as stationary phase, and a mixture of methanol and 50 mM choline buffer (pH 3.5) as mobile phase. After formation of the bromophenacyl derivative, betaine was detected at 254 nm with a detection limit of 0.2 microgram/ml. The method was successfully used to analyze several Echinacea market products, and significant variations in their betaine content from 0.04 to 0.64% were observed.

Betaine↗
PubMed2001

In their own words: using the common sense model to analyze patient descriptions of cancer-related fatigue.

PURPOSE/OBJECTIVES: To describe cancer-related fatigue (CRF) from the perspective of individuals experiencing it and examine the fit of their descriptions with the concepts from the Common Sense Model (CSM). DESIGN: Exploratory, qualitative design, SAMPLE: A convenience sample of eight patients with cancer known to be experiencing fatigue from the outpatient clinic. METHODS: Content analysis of data obtained from focus groups. FINDINGS: All statements describing CRF could be classified using the major constructs of the CSM: representation, coping, and appraisal. The majority of statements were classified as representations of fatigue (67%), with smaller proportions classified as coping (26%) and appraisal (7%). CONCLUSIONS: This study provides evidence to support the validity of the CSM constructs as an organizing framework in the conduct of research. IMPLICATIONS FOR NURSING PRACTICE: This study demonstrates the usefulness of the model In clinical assessment of patient representations of CRF as well as coping strategies for managing it The model is particularly useful in targeting knowledge deficits and inaccuracies.

Adaptation, Psychological↗
PubMed2000

Notch signaling enhances survival and alters differentiation of 32D myeloblasts.

The Notch transmembrane receptors play important roles in precursor survival and cell fate specification during hematopoiesis. To investigate the function of Notch and the signaling events activated by Notch in myeloid development, we expressed truncated forms of Notch1 or Notch2 proteins that either can or cannot activate the core binding factor 1 (CBF1) in 32D (clone 3) myeloblasts. 32D cells proliferate as blasts in the presence of the cytokines, GM-CSF or IL-3, but they initiate differentiation and undergo granulopoiesis in the presence of granulocyte CSF (G-CSF). 32D cells expressing constitutively active forms of Notch1 or Notch2 proteins that signal through the CBF1 pathway maintained significantly higher numbers of viable cells and exhibited less cell death during G-CSF induction compared with controls. They also displayed enhanced entry into granulopoiesis, and inhibited postmitotic terminal differentiation. In contrast, Notch1 constructs that either lacked sequences necessary for CBF1 binding or that failed to localize to the nucleus had little effect. Elevated numbers of viable cells during G-CSF treatment were also observed in 32D cells overexpressing the basic helix-loop-helix protein (bHLH), HES1, consistent with activation of the CBF1 pathway. Taken together, our data suggest that Notch signaling enhances 32D cell survival, promotes entry into granulopoiesis, and inhibits postmitotic differentiation through a CBF1-dependent pathway.

Animals↗
PubMed2000

The application of high permittivity piezoelectric ceramics to 2D array transducers for medical imaging.

Two-dimensional (2D) array transducers have become of great interest in the last few years, in view of real-time volumetric ultrasonic imaging. The electrical matching between the high electrical impedance of elements and the standard cables and electronics is one of the key issues in 2D array design. The use of high-permittivity ceramics such as PNNZT either in bulk configuration or in 1-3 piezocomposites decreases the electrical impedance. In this paper, bulk samples of PNNZT and PZT ceramics are characterised, and results are compared. 2D array elements are then manufactured and their electrical impedances measured. Theoretical predictions of homogenisation models for 1-3 piezocomposites allow the simulation of the electroacoustic behaviour of 2D array elements. Results for both piezocomposite and bulk materials can be obtained. Calculations of the input impedance, the sensitivity and the bandwidth of the different configurations are compared and discussed. These results demonstrate the advantages of the PNNZT compositions over standard PZT.

Acoustics↗
PubMed2000

Nurses' perceptions of multidisciplinary teamwork in acute psychiatric settings.

The findings of a pilot telephone survey of senior nurses' views of multidisciplinary teamwork (MDT) practice in 26 acute psychiatric admission wards within the ambit of one English health authority are reported. The survey was conducted in two stages. The first stage focused on obtaining the senior nurse's general perceptions of the organization of the work of the multidisciplinary team, and in the second stage more detailed responses to the original questions were obtained. The findings suggest that the composition and operations of the acute ward team are limited, and the relationship between the MDT and patients and their families do not entirely support the concept of increased collaboration with patients and their families. The findings are discussed within the context of the perceived crisis in acute psychiatric care in England and the ambitions for more egalitarian 'mental health' services.

Acute Disease↗
PubMed2000

The required role of the psychiatric-mental health nurse in primary health-care: an augmented Delphi study.

An augmented Delphi study was employed to elicit the perceptions of CPNs, GPs, social workers, managers of psychiatric nursing services and health service purchasers in England, on the role required of a psychiatric (mental health) nurse in primary health care. In the final stage of the study, users of mental health service were enlisted in a verification study of the emergent findings. A broad consensus emerged that a gap existed in mental health services in primary care. This was perceived as placing a large burden on GPs, which might be reduced by the appropriate development of community psychiatric-mental health nursing. The study suggested the possibilities for development of a 'mental health nurse consultant' role, which might augment the current CPN role, within which the nurse might offer not only direct patient care, but also support to members of the primary care team.

Attitude of Health Personnel↗
PubMed2000

Survey of dietetic provision for patients with diabetes.

AIMS: To survey dietitians involved in diabetes care regarding the provisions for patients with diabetes. METHODS: A national survey of 512 dietitians known to be engaged in provision of diabetes care was conducted in 1997 and 391 (76%) responded. RESULTS: Nationally the median provision of dietetic care for diabetes reported was 10.7 h per 100,000 general population per week, but the provision was uneven ranging from 2.0 to 27.6 h per 100,000. Eighty-five per cent of dietitians worked in areas where the provision was less than 22 h per 100,000 general population per week (the current recommended minimum standard). Dietetic provision was greater in secondary care (median 9.1 h per 100,000 general population per week) than in general practice, residential homes and other locations (median 4.4 h per 100,000 general population per week). Provision was greater in those areas in which a designated dietitian had responsibility for co-ordinating the dietetic service for diabetes than in areas where the co-ordinator was not a dietitian or where there was no co-ordinator. Over 90% of dietitians reported following British Diabetic Association (BDA) recommendations regarding advice on carbohydrate, sugar, fat and fibre consumption, but only one-third routinely advised on salt restriction. Of the 17% of dietitians who continue to use carbohydrate exchanges, all combine this method with other approaches. Of the recommendations made by the Clinical Standards Group, only 69% of dietitians reported seeing more than half of newly diagnosed adult patients within four weeks, and less than 50% reported offering half or more of their patients an annual review. Amongst the literature in current use, 98% of dietitians use BDA literature for teaching patients and 90% use BDA publications in their own education. Seventy-six per cent of dietitians believed that there was a role for commercial slimming organizations in weight management of people with diabetes. CONCLUSIONS: Given the proven value of dietetic input in diabetes management, there would be advantages to correcting the regional inequalities in dietetic provision for diabetes care in the UK.

Adult↗