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Biomedical subjects

L Walker

Publications and source records attributed to L Walker.

At least 55 records · Page 3Linked to original sources
PubMed1999

Endovascular Doppler guide wire in renal arteries. Correlation with angiography in 20 patients.

RATIONALE AND OBJECTIVES: To evaluate the feasibility of endovascular Doppler recording in renal arteries and to compare the reliability of Doppler parameters for detection of renal artery stenosis. METHODS: The authors examined 36 renal arteries in 20 patients with a 0.018" endovascular flow wire. Peak systolic velocity and the renal artery-to-aortic peak were measured in the main renal artery. From intrarenal waveforms, acceleration, acceleration time, and the renal resistive index were obtained. Spectral analysis with consensus scoring of early systolic peak was also performed. RESULTS: Twelve significantly stenosed renal arteries and 26 normal renal arteries were examined with the Doppler guide wire, without complications. Peak systolic velocity was the only parameter significantly different in renal artery stenosis (P = 0.037). Peak systolic velocity also differed significantly between hypertensive and normotensive patients. Tardus parvus was specific for severe renal artery stenosis. CONCLUSIONS: Endovascular Doppler is a safe and accurate method for the determination of velocity measurements and may be useful during percutaneous renal artery revascularization.

Aged↗
PubMed1999

How RhoGDI binds Rho.

Like all Rho (Ras homology) GTPases, RhoA functions as a molecular switch in cell signaling, alternating between GTP- and GDP-bound states, with its biologically inactive GDP-bound form maintained as a cytosolic complex with RhoGDI (guanine nucleotide-exchange inhibitor). The crystal structures of RhoA-GDP and of the C-terminal immunoglobulin-like domain of RhoGDI (residues 67-203) are known, but the mechanism by which the two proteins interact is not known. The functional human RhoA-RhoGDI complex has been expressed in yeast and crystallized (P6(5)22, unit-cell parameters a = b = 139, c = 253 A, two complexes in the asymmetric unit). Although diffraction from these crystals extends to 3.5 A and is highly anisotropic, the experimentally phased (MAD plus MIR) electron-density map was adequate to reveal the mutual disposition of the two molecules. The result was validated by molecular-replacement calculations when data were corrected for anisotropy. Furthermore, the N-terminus of RhoGDI (the region involved in inhibition of nucleotide exchange) can be identified in the electron-density map: it is bound to the switch I and switch II regions of RhoA, occluding an epitope which binds Dbl-like nucleotide-exchange factors. The entrance of the hydrophobic pocket of RhoGDI is 25 A from the last residue in the RhoA model, with its C-terminus oriented to accommodate the geranylgeranyl group without conformational change in RhoA.

Binding Sites↗
PubMed1999

Validity of three measures of severity of AIDS for use in health services research studies.

Policy makers and hospital managers often use severity adjustments as a control for patient mix differences when evaluating outcomes of care. Unfortunately, few indices are carefully examined and therefore the evaluations based on these methods of severity adjustment are suspect. This paper examines the accuracy of three indices for measuring the severity of illness of AIDS patients. We examine the Diagnosis-Based Severity Index (DBSI), a modified version of DBSI referred to as MDBSI and the Composite Laboratory Index (CLI) in predicting survival of AIDS patients at one medical centre. We analysed the correlation between indices and months of survival. We also examined the percentage of variance in survival months explained by each index separately and together. Finally, we used survival analysis to examine whether DBSI classifies patients in groups with distinct patterns of survival. Only patients who had died were included in the analysis so that information on the patients' full course of illness was available. Of the 91 patients abstracted, 81 cases had date of AIDS, date of death, and the CLI. These 81 cases were the focus of the analysis. Both CLI and DBSI were predictive of months of survival but were not correlated to each other. Predictions of months of survival were improved if both indices were used together rather than separately. Survival analysis confirmed that patients classified by DBSI had distinctly different survival patterns. Each index measures different aspects of the severity of the patient's condition and when possible both indices should be used together. When laboratory data are not available, e.g. in Medicaid administrative files, the use of DBSI may be reasonable.

Acquired Immunodeficiency Syndrome↗
PubMed1999

'We want an allocation to theatre!' Diploma level nursing students have their say.

The aim of this study was to ascertain the perceptions of diploma level nursing students towards theatre nursing and whether these perceptions had any influenced on their choosing a career in operating department nursing. The study was qualitative in its approach, using a questionnaire as the main research tool, to focus on thirty-three second year diploma level nursing students. The main findings were that 94% of the students felt that a set allocation to the operating theatre would be invaluable, as it would enhance the nursing care they gave to their patients on the ward. The study also found that the students did not have a real understanding of the theatre nurse's role, with only one third of the students seeing the theatre nurse carrying out patient care. This perceived lack of patient care had a major effect on them not wishing to choose theatre nursing as a career, once qualified. The results of this study suggest that the profile of theatre nursing must be raised to attract greater numbers of students to the speciality.

Attitude of Health Personnel↗
PubMed1999

Developing individualized care in nursing homes: integrating the views of nurses and certified nurse aides.

Despite recent attention devoted to the development of individualized care in nursing homes, empirical research assessing changes in practice is quite limited, and very few studies have explored specifically the experiences and perceptions of certified nurse aides (CNAs). This study reports findings from a comparative analysis conducted on a data set including quantitative and qualitative data from CNAs (N = 289) and nurses in Connecticut (N = 245). Measures of obstacles to individualized care and needs for future supports were explored. A number of significant differences in perceptions of obstacles to providing individualized care were found. The nurses were significantly more likely to identify the following impediments to change: cost (p < .0001), concepts not integrated into work (p < .0001), lack of administrative support (p < .10), and staff attitudes (p < .10). The CNAs were significantly more likely to report inadequate staffing (p < .001), lack of interdisciplinary teams (p < .001), and resident and family attitudes (p < .01) as problematic. These findings suggest substantial discordance among nurses and CNAs on a number of important issues surrounding individualized care. Such disparate perceptions pose challenges to nursing homes committed to the implementation of individualized care alternatives. Successful approaches must consider the various vantage points of caregivers and administrators.

Aged↗
PubMed1998

Real-time quantitative measurement of autocrine ligand binding indicates that autocrine loops are spatially localized.

Autocrine ligands are important regulators of many normal tissues and have been implicated in a number of disease states, including cancer. However, because by definition autocrine ligands are synthesized, secreted, and bound to cell receptors within an intrinsically self-contained "loop," standard pharmacological approaches cannot be used to investigate relationships between ligand/receptor binding and consequent cellular responses. We demonstrate here a new approach for measurement of autocrine ligand binding to cells, using a microphysiometer assay originally developed for investigating cell responses to exogenous ligands. This technique permits quantitative measurements of autocrine responses on the time scale of receptor binding and internalization, thus allowing investigation of the role of receptor trafficking and dynamics in cellular responses. We used this technique to investigate autocrine signaling through the epidermal growth factor receptor by transforming growth factor alpha (TGFalpha) and found that anti-receptor antibodies are far more effective than anti-ligand antibodies in inhibiting autocrine signaling. This result indicates that autocrine-based signals can operate in a spatially restricted, local manner and thus provide cells with information on their local microenvironment.

Animals↗
PubMed1998

Molecular mechanisms of auxin action.

The plant growth hormone auxin has an important role in a variety of plant growth and developmental processes. Identification of transcription factors, some with defined genetic function, has shed new light on the mechanisms of auxin regulated gene expression. In addition, the molecular characterization of genes required for auxin response indicates that regulated protein degradation by the ubiquitin-proteosome pathway has an important function in auxin action.

Arabidopsis↗
PubMed1998

Medicaid estate planning: practices and perceptions of Medicaid workers, elder law attorneys, and certified financial planners.

This study examined Medicaid estate planning (MEP) through the experiences and perceptions of three groups in Connecticut: Medicaid eligibility workers (n = 128), elder law attorneys (n = 41), and certified financial planners (n = 29). Respondent groups varied significantly with regard to their perceptions of prevalence and magnitude of MEP, the nature of transferred assets, mechanisms for transfers, and characteristics of the "typical" client participating in asset divestiture for the purpose of qualifying for Medicaid. This substantial lack of concordance among those professionals most closely involved with MEP poses challenges for policy and research in this area.

Aged↗
PubMed1998

A randomised controlled trial of postal versus interviewer administration of a questionnaire measuring satisfaction with, and use of, services received in the year before death.

STUDY OBJECTIVES: To develop a short form of an interview schedule used successfully in previous national surveys of care for the dying, and to investigate the effect of administering it by post on response rate, response bias and on the nature of responses to questions. DESIGN: Randomised controlled trial. SETTING: An inner London health authority. PARTICIPANTS: Informants (person registering death) of random sample of cancer deaths between June 1995 and July 1996. MAIN RESULTS: The shortened questionnaire (VOICES) has 158 questions. Response rate did not differ significantly between postal and interview groups (interview; 56% (69 of 123), postal: 52% (161 of 308). Responders in the two groups did not differ in terms of their sociodemographic characteristics. Postal questionnaires had significantly more missing data, particularly on questions about service provision and satisfaction with services. Responses to questions differed between the groups on 11 of 158 questions. Interview group respondents were more likely to give top ranking responses to questions on service satisfaction and symptom control. CONCLUSIONS: Postal questionnaires are an acceptable alternative to interviews in retrospective post-bereavement surveys of care for the dying, at least in terms of response rate and response bias. However, the increased costs of interview surveys need to be balanced against the fact that postal questionnaires result in more missing data, and possibly less reliable answers to some questions. Caution is needed in combining results from the two data collection methods as interview respondents gave more positive answers to some questions.

Adult↗
PubMed1998

Microbial contamination of three-way taps on arterial lines.

Arterial lines with three-way taps are used to measure blood pressure and aspirate blood, and are a potential source of catheter-related sepsis. Swabs were taken daily from 118 three-way taps on 98 arterial lines in a general intensive care unit. Infusion lines were changed weekly but arterial cannulae were not changed routinely. An overall contamination rate of 24.6% was found with the predominant organism being coagulase negative staphylococcus. The three-way taps became increasingly contaminated with time but this was shown to be unrelated to the manipulation rates. Blood culture organisms in those showing contamination of the three-way taps showed no relationship to the bacteria causing the contamination.

Arteries↗
PubMed1998

[Contribution of chromosomal abnormalities to in vitro fertilization failures].

BACKGROUND: Present knowledge of mechanisms involved in human fertilization has uncovered a new group of pathologic conditions that have been generically named fertilization abnormalities. AIM: To determine the contribution of chromosomal alterations to in vitro fertilization failures. MATERIALS AND METHODS: A cytogenetic analysis of oocytes that were not fertilized after insemination with normal spermatozoa. Oocytes were obtained from patients subjected to in vitro fertilization in a public hospital of Metropolitan Santiago. Ovulation was induced in these patients administering GnRh-a, FSH, HMG and HCG. The double fixation technique described by Wramsby was used to obtain chromosomes. RESULTS: One hundred and seven oocytes coming from 45 women aged 25 to 42 years old were studied. The frequency of aneuploidy in these oocytes was 37.3%, with a 11.8% of hypohaploidy, a 21.6% of hyperhaploidy and a 3.9% of diploid oocytes. In hyperhaploid as well as in hypohaploid oocytes, the chromosomes involved in aneuploidy pertained to groups D. and G. CONCLUSIONS: Although the total frequency of aneuploidy is within normal ranges, the frequency of hyperhaploidy is superior to previous reports. An explanation for this finding could be that the occurrence of a lack of disjunction with chromosomal retention in the parental cell occurs with a higher frequency than that in which the chromosomes are retained in the polocyte. We also suggest that oocyte chromosomal aneuploidy could contribute to the failure of in vitro fertilization procedures.

Adult↗
PubMed1997

Preadmission testing.

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Ambulatory Surgical Procedures↗
PubMed1997

Periotest values of dental implants in the first 2 years after second-stage surgery: DICRG interim report no. 8. Dental Implant Clinical Research Group.

In 1991, the Dental Implant Clinical Research Group initiated a long-term clinical study in cooperation with the Department of Veterans Affairs to investigate the influence of implant design, application, and site of placement on clinical performance and crestal bone height. As part of this investigation, Periotest values for 2,212 root from implants were determined at second-stage surgery and during a 24-month follow-up period. Mean Periotest values decreased for implants placed in quality 1 and 2 bone, did not change for implants in quality 3 bone, and increased for implants in quality 4 bone. Implants in the posterior maxilla and single implants in the anterior maxilla had increasing mean Periotest values as compared with decreasing values for implants in other regions. Mean Periotest values for uncoated implants decreased gradually to approach those of hydroxyapatite-coated implants.

Adult↗