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David Johnson

Publications and source records attributed to David Johnson.

At least 109 records · Page 6Linked to original sources
PubMed2002

Detection and mutation of a luxS-encoded autoinducer in Proteus mirabilis.

Quorum sensing regulates the expression of virulence factors in a wide variety of pathogenic bacteria. This study has shown that Proteus mirabilis harbours a homologue of luxS, a gene required for the synthesis of the quorum sensing autoinducer 2 (AI-2). AI-2 activity is expressed during and is correlated with the initiation of swarming migration on agar surfaces. The P. mirabilis luxS locus was cloned and a LuxS(-) strain constructed by allelic-exchange mutagenesis. While lacking AI-2 activity, a null mutation in luxS, however, did not affect swimming or swarming motility, swarmer cell differentiation, or virulence in a mouse model of ascending urinary tract infection.

Animals↗
PubMed2002

A review of medical imaging informatics.

This review of medical imaging informatics is a survey of current developments in an exciting field. The focus is on informatics issues rather than traditional data processing and information systems, such as picture archiving and communications systems (PACS) and image processing and analysis systems. In this review, we address imaging informatics issues within the requirements of an informatics system defined by the American Medical Informatics Association. With these requirements as a framework, we review, in four sections: (1) Methods to present imaging and associated data without causing an overload, including image study summarization, content-based medical image retrieval, and natural language processing of text data. (2) Data modeling techniques to represent clinical data with focus on an image data model, including general-purpose time-based multimedia data models, health-care-specific data models, knowledge models, and problem-centric data models. (3) Methods to integrate medical data information from heterogeneous clinical data sources. Advances in centralized databases and mediated architectures are reviewed along with a discussion on our efforts at data integration based on peer-to-peer networking and shared file systems. (4) Visualization schemas to present imaging and clinical data: the large volume of medical data presents a daunting challenge for an efficient visualization paradigm. In this section we review current multimedia visualization methods including temporal modeling, problem-specific data organization, including our problem-centric, context and user-specific visualization interface.

Databases, Factual↗
PubMed2002

Designing a patient education framework via use case analysis.

One of the challenges of developing patient education content in electronic form is to determine the information and interaction needs that motivate a patient to learn in the first place. We have found that use case analysis of patient education helps in clarifying the types of information and interaction required to educate a patient effectively. This paper presents a use case model for patient education as well as a Java-based framework that facilitates both the extension and updating of individually tailored, electronic patient education content. The framework defines an abstract interface that represents a particular panel of information, and provides a content manager that dynamically discovers and refreshes new panels as they are added or modified.

Computational Biology↗
PubMed2002

Cell surface major histocompatibility complex class II proteins are regulated by the products of the gamma(1)34.5 and U(L)41 genes of herpes simplex virus 1.

Modulation of host immune responses has emerged as a common strategy employed by herpesviruses both to establish life-long infections and to affect recovery from infection. Herpes simplex virus 1 (HSV-1) blocks the major histocompatibility complex (MHC) class I antigen presentation pathway by inhibiting peptide transport into the endoplasmic reticulum. The interaction of viral gene products with the MHC class II pathway, however, has not been thoroughly investigated, although CD4(+) T cells play an important role in human recovery from infection. We have investigated the stability, distribution, and state of MHC class II proteins in glioblastoma cells infected with wild-type HSV-1 or mutants lacking specific genes. We report the following findings. (i) Wild-type virus infection caused a decrease in the accumulation of class II protein on the surface of cells and a decrease in the endocytosis of lucifer yellow or dextran conjugated to fluorescein isothiocyanate but no decrease in the total amount of MHC class II proteins relative to the levels seen in mock-infected cells. (ii) Although the total amount of MHC class II protein remained unchanged, the amounts of cell surface MHC class II proteins were higher in cells infected with the U(L)41-negative mutant, which lacks the virion host shutoff protein, and especially high in cells infected with the gamma(1)34.5-negative mutant. We conclude that infected cells attempt to respond to infection by increased acquisition of antigens and transport of MHC class II proteins to the cell surface and that these responses are blocked in part by the virion host shutoff protein encoded by the U(L)41 gene and in large measure by the direct or indirect action of the infected cell protein 34.5, the product of the gamma(1)34.5 gene.

Antigen Presentation↗
PubMed2002

Continuity of care and health decline associated with a hip fracture.

OBJECTIVES: Identify determinants of health decline associated with hip fracture with the goal of designing interventions. METHOD: Prefracture and postfracture information was obtained from participants aged 65-plus years fracturing a hip between July 1996 and August 1997. Health utilization data were linked to the cohort data and to an age-gender matched cohort of nonfracture seniors. RESULTS: Fracture patients were likely to have been hospitalized and have low continuity of care. Patients making frequent physician visits were at increased risk of both prefracture hospitalization and postfracture health decline. Prefracture hospitalization was less likely for patients with high physical function; patients of high mental status were less likely to experience postfracture health decline. DISCUSSION: Health appears to be in decline prefracture. Patients may benefit from continuous physician care to prevent further health deterioration. Some hip fractures can be prevented by identifying high-risk seniors at an early stage and intervening to prevent falls.

Aged↗
PubMed2002

Hot flashes and related outcomes in breast cancer survivors and matched comparison women.

PURPOSE/OBJECTIVES: To compare the hot flash symptom experience and related outcomes between breast cancer survivors and healthy women. DESIGN: Descriptive, cross-sectional, comparative study. SETTING: Southeastern university medical center. SAMPLE: 69 of 207 breast cancer survivors contacted via a tumor registry and 63 age-matched healthy female volunteers. Survivors were a mean of 57 years and a mean of 39 months postdiagnosis. METHODS: Mailed survey included a demographic, disease, and treatment information form; a gynecologic history form; a two-day, prospective, hot flash diary; a detailed hot flash questionnaire; mood and affect scales; and the Hot Flash-Related Daily Interference Scale. MAIN RESEARCH VARIABLES: Hot flashes, mood, affect, interference with daily activities, and overall quality of life. FINDINGS: Breast cancer survivors had hot flashes that were significantly more frequent, severe, distressing, and of greater duration. Breast cancer survivors were less likely to be using hormone replacement and more likely to have tried nonhormonal prescription interventions in the past, but reported significantly less effectiveness from hot flash treatments. Breast cancer survivors with severe hot flashes reported significantly greater mood disturbance; higher negative affect; more interference with daily activities, including sleep, concentration, and sexuality; and poorer overall quality of life in comparison to breast cancer survivors with no hot flashes to mild hot flashes. Hot flash quality and triggers were not significantly different between groups. No clear temporal pattern of hot flashes emerged. CONCLUSIONS: Hot flashes are a significant problem for breast cancer survivors, even for those who are naturally postmenopausal (i.e., did not undergo menopause as a result of surgery or the effects of chemotherapy). Hot flashes remained fairly stable over time and did not diminish in frequency, severity, or associated distress. IMPLICATIONS FOR NURSING: The findings guide the assessment of the uniqueness of the problem of hot flashes experienced by breast cancer survivors and help define outcomes to address in clinical practice or include in future hot flash intervention research.

Affect↗
PubMed2002

Caller satisfaction with after-hours telephone advice: nurse advice service versus on-call pediatricians.

OBJECTIVE: To compare caller satisfaction with after-hours medical advice provided by a for-profit nurse advice service with advice provided by on-call pediatricians. METHODS: The study setting was the general pediatrics faculty practice of an urban university medical center. Participants were parents or guardians of a population of approximately 6000 children calling for after-hours medical advice over a 10-month period from January 18 to November 20, 2000. After-hours medical advice calls were randomized to either a nurse advice service or the on-call pediatrician. Caller satisfaction and subsequent health care utilization were measured by a telephone survey of callers and review of all health care visits within 3 days of the initial telephone advice call. RESULTS: Five hundred sixty-six (48%) callers were enrolled in the on-call pediatrician group, and 616 (52%) were enrolled in the advice nurse group. Caller satisfaction was rated as very good or excellent significantly more often for the on-call pediatrician than for the nurse advice service as follows: telephone call overall (68.5% vs 55.0%; 95% confidence interval [CI] of difference: 8.0%-19.0%), thoroughness and competence of the person they spoke with (74.0% vs 59.1%; 95% CI of difference: 9.6%-20.2%), courtesy and friendliness of the person they spoke with (77.4% vs 73.9%; 95% CI of difference: -1.4%-8.4%), length of time spent waiting (70.8% vs 60.1%; 95% CI of difference: 5.4%-16.2%), time spent talking with the on-call pediatrician or advice nurse (68.2% vs 52.4%; 95% CI of difference: 10.2%-21.3%), and the medical advice given (68.6% vs 53.9%; 95% CI of difference: 9.2%-20.1%). Compliance with the advice given was significantly higher for office care in the on-call pediatrician group (51.5% vs 29.6%; 95% CI of difference: 8.9%-34.2%). Repeat calls for advice were significantly more frequent for the nurse advice service, both within 4 hours (13.0% vs 4.8%; 95% CI of difference: 5.0%-11.4%), and within 72 hours (23.4% vs 13.3%; 95% CI of difference: 5.8%-14.5%). CONCLUSION: Callers were less satisfied with medical advice provided by a nurse advice service compared with the traditional on-call pediatrician. The lower satisfaction was associated with somewhat poorer compliance with recommended triage dispositions and more frequent repeat calls for medical advice.

Child↗
PubMed2002

Health service costs for patients on the waiting list.

OBJECTIVE: To find out if the cost of health services was artificially increased because of a delay in surgery due to a lack of resources. DESIGN: A retrospective cohort study. SETTING: Three urban hospitals in Calgary, Alta. PATIENTS: The study cohort comprised 4441 patients (1 index procedure for each patient). INTERVENTIONS: Cholecystectomy, discectomy, hysterectomy, total knee and total hip replacements. OUTCOME MEASURES: The costs for physician claims, use of home care and pharmaceutical prescriptions 1 year before and after the selected procedures, using 1997/98 administrative records and waiting times maintained by Alberta Health and Wellness and Calgary Regional Health Authority. RESULTS: The median wait for joint surgery (88 d for knee replacements and 65 d for hip replacements) was longer than for the other selected procedures (29 d for cholecystectomies, 21 d for discectomies and 42 d for hysterectomies). Total per patient physician claim costs decreased after surgery (cholecystectomy--30%, discectomy--24%, hip replacement--6%, hysterectomy--23% and knee replacement--4%). Seeing the procedure specialist more than once preoperatively was associated with a greater decrease in postoperative physician claim costs. Longer waits were not associated with more physician claim costs or Blue Cross prescriptions claim costs for seniors (> or = 65 yr) in the year before or after surgery nor were they associated with more physician claim costs during the actual wait compared with a matched postoperative time period. CONCLUSIONS: No evidence was found to suggest that waiting for 1 of 5 common surgical procedures is correlated with greater health service expenditures pre- or postoperatively. In this study, wait time is not a proxy for health service use nor do health service costs decrease markedly after surgery.

Alberta↗
PubMed2002

Low-volume obstetrics. Characteristics of family physicians' practices in Alberta.

OBJECTIVE: To compare the obstetric practices of family physicians who attended fewer than 25 births per year (low-volume) with the practices of family physicians who attended more than 25 births per year (high-volume) and the practices of obstetricians. DESIGN: Retrospective cohort study using data from administrative databases. SETTING: Alberta. PARTICIPANTS: All physicians who provided intrapartum care between April 1, 1997, and March 31, 2000. MAIN OUTCOME MEASURES: Type of delivery, size of hospitals where deliveries took place, characteristics of patients, and number of medical interventions. RESULTS: Of 1026 family physicians, 543 (53%) were low-volume providers of intrapartum care. In 1997-1998, low-volume family physicians (LVFPs) attended 24% of all vaginal and cesarean births attended by family physicians; by 1998-1999, that percentage had decreased to 9%; and by 1999-2000, to 5%. In contrast, the number of births attended by all family physicians remained relatively constant at 43% during the 3 years. In hospitals that had fewer than 50 deliveries a year, LVFPs attended almost half the births. Although LVFPs did fewer medical inductions, vacuum extractions, and epidural anesthetics and more forceps extractions, episiotomies, and cesarean sections than high-volume family physicians (HVFPs), the differences between their practices were much smaller than the differences between all family physicians' practices and the practices of obstetricians (who treat higher-risk mothers and newborns). CONCLUSION: The decrease in LVFPs' obstetric practices could make a pronounced difference at smaller hospitals where most low-volume practice occurs.

Alberta↗
PubMed2002

Variations in treatment of femoral neck fractures in Alberta.

OBJECTIVES: To examine, in the province of Alberta, temporal trends, regional variations in treatment options and in-hospital death rates after a femoral neck fracture. DESIGN: A retrospective cohort study. PATIENTS: Six years' data were abstracted from the Alberta Morbidity File, the Alberta Health Stakeholder File and the Alberta Health Care Claims File. Patients were included if they were Alberta residents, aged 65 years or older, had sustained a femoral neck fracture and had undergone internal fixation, hemiarthroplasty or total hip arthroplasty. MAIN OUTCOME MEASURES: Death rates, arthroplasty rates and hospital stay. RESULTS: In-hospital death rates were similar across hospitals, with risks being higher for men, patients aged 80 years or older and those with more comorbid conditions. Arthroplasty rates varied from 58% to 77% among hospitals, and hospital stays associated with arthroplasty were significantly longer than those associated with internal fixation. The chance of undergoing arthroplasty varied from hospital to hospital by gender and by the number of comorbid conditions. CONCLUSION: Regional variations suggest lack of agreement among Alberta's surgeons as to how best to treat femoral neck fractures.

Aged↗
PubMedDate not supplied

Expression profiling of herpesvirus and vaccinia virus proteins using a high-throughput baculovirus screening system.

We have developed a high-throughput system for generating baculoviruses and testing the expression, solubility, and affinity column purification of encoded proteins. We have used this system to generate baculoviruses for and analyze the expression of 337 proteins from three different herpesviruses (HSV-1, EBV, and CMV) and vaccinia virus. Subsets of these proteins were also tested for expression and solubility in E. coli. Comparisons of the results in the two systems are presented for each virus.

Animals↗
PubMedDate not supplied

Editorial.

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Brain Injuries↗