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David Johnson

Publications and source records attributed to David Johnson.

At least 37 records · Page 2Linked to original sources
PubMed2002

Arctic microorganisms respond more to elevated UV-B radiation than CO2.

Surface ultraviolet-B radiation and atmospheric CO2 concentrations have increased as a result of ozone depletion and burning of fossil fuels. The effects are likely to be most apparent in polar regions where ozone holes have developed and ecosystems are particularly sensitive to disturbance. Polar plant communities are dependent on nutrient cycling by soil microorganisms, which represent a significant and highly labile portion of soil carbon (C) and nitrogen (N). It was thought that the soil microbial biomass was unlikely to be affected by exposure of their associated plant communities to increased UV-B. In contrast, increasing atmospheric CO2 concentrations were thought to have a strong effect as a result of greater below-ground C allocation. In addition, there is a growing belief that ozone depletion is of only minor environmental concern because the impacts of UV-B radiation on plant communities are often very subtle. Here we show that 5 years of exposure of a subarctic heath to enhanced UV-B radiation both alone and in combination with elevated CO2 resulted in significant changes in the C:N ratio and in the bacterial community structure of the soil microbial biomass.

Arctic Regions↗
PubMed2002

Genomic screening of fibroblast growth-factor receptor 2 reveals a wide spectrum of mutations in patients with syndromic craniosynostosis.

It has been known for several years that heterozygous mutations of three members of the fibroblast growth-factor-receptor family of signal-transduction molecules-namely, FGFR1, FGFR2, and FGFR3-contribute significantly to disorders of bone patterning and growth. FGFR3 mutations, which predominantly cause short-limbed bone dysplasia, occur in all three major regions (i.e., extracellular, transmembrane, and intracellular) of the protein. By contrast, most mutations described in FGFR2 localize to just two exons (IIIa and IIIc), encoding the IgIII domain in the extracellular region, resulting in syndromic craniosynostosis including Apert, Crouzon, or Pfeiffer syndromes. Interpretation of this apparent clustering of mutations in FGFR2 has been hampered by the absence of any complete FGFR2-mutation screen. We have now undertaken such a screen in 259 patients with craniosynostosis in whom mutations in other genes (e.g., FGFR1, FGFR3, and TWIST) had been excluded; part of this screen was a cohort-based study, enabling unbiased estimates of the mutation distribution to be obtained. Although the majority (61/62 in the cohort sample) of FGFR2 mutations localized to the IIIa and IIIc exons, we identified mutations in seven additional exons-including six distinct mutations of the tyrosine kinase region and a single mutation of the IgII domain. The majority of patients with atypical mutations had diagnoses of Pfeiffer syndrome or Crouzon syndrome. Overall, FGFR2 mutations were present in 9.8% of patients with craniosynostosis who were included in a prospectively ascertained sample, but no mutations were found in association with isolated fusion of the metopic or sagittal sutures. We conclude that the spectrum of FGFR2 mutations causing craniosynostosis is wider than previously recognized but that, nevertheless, the IgIIIa/IIIc region represents a genuine mutation hotspot.

Acrocephalosyndactylia↗
PubMed2002

Hospital practice more than specialty influences the choice of regional or general anesthesia for Cesarean section.

PURPOSE: Describe the influence of specialty certification and practice style upon the anesthetic technique used for Cesarean deliveries. METHODS: Alberta physician claims and hospital abstracts between April 1, 1998 to March 31, 2000 were used to determine the technique of anesthesia (regional or general). The influence of practice (volume of deliveries, geographic location, presence of regional analgesia providers) and specialty (anesthesiologist or family/general practice) is explored by logistic regression. RESULTS: Hospital abstracts of 13,884 Cesarean sections were analyzed. Anesthesiologists performed 76% of the anesthetics: epidural (33%), spinal (45%), and general anesthesia (22%). Comparing only regional and metropolitan hospitals, the percent of general anesthesia performed by anesthesiologists varied between 5% to 50%. After adjusting for other factors, we found, in order of importance, the following determined the use of general anesthesia for Cesarean sections: 1) hospitals with more epidural procedure providers during labour were 3% less likely to have providers choose general anesthesia; 2) larger, regional and metropolitan hospitals were less likely to have providers choose general anesthesia; 3) hospitals with a high volume epidural procedure provider during labour were 64% less likely to have providers choose general anesthesia; 4) anesthesiologists were 32% less likely to choose general anesthesia. CONCLUSION: The overall use of regional anesthesia for Cesarean sections in Alberta is high. The chance of receiving a general anesthetic for a Cesarean delivery varies across the province and was more related to practice environment than specialty.

Adult↗
PubMed2002

Declining hemoglobin during chemoradiotherapy for locally advanced non-small cell lung cancer is significant.

BACKGROUND AND PURPOSE: Tumor hypoxia and anemia have been linked to poor overall survival and local control in carcinomas of both the uterine cervix and the head and neck for patients undergoing radiotherapy. Little is known about the effect of these factors on the outcome of NSCLC patients with locally advanced disease undergoing chemoradiation therapy. MATERIALS AND METHODS: To examine the impact of anemia in stage III NSCLC patients undergoing combined modality therapy, we reviewed our database from three sequential trials of concurrent weekly paclitaxel +/- carboplatin and radiation therapy. 115 pts from 17 institutions were enrolled from 4/94 to 5/97. In this series, hemoglobin values were collected before treatment and weekly during radiotherapy. We correlated baseline Hb and Hb changes during chemoradiation treatment with overall survival. RESULTS: Although pretreatment anemia was common (30% Hb = 110-130 g/l, 16% Hb <110 g/l), log-rank analyses of presenting Hb, average Hb and minimum Hb during treatment were not statistically significantly predictive of survival. However in a Cox model, declining hemoglobin during chemoradiation had a statistically significant impact on survival. CONCLUSIONS: These analyses reveal that a decline in hemoglobin during chemoradiation for stage III NSCLC has a statistically significant correlation with overall survival. Strategies maximizing hemoglobin during combined modality therapy need further exploration in well-planned randomized trials.

Adult↗
PubMed2002

Influence of aboriginal and socioeconomic status on birth outcome and maternal morbidity.

OBJECTIVE: To assess the association of Aboriginal and socioeconomic status with birth outcome and maternal morbidity in Alberta. METHODS: A retrospective cohort study using Alberta health service and vital statistics data from 1997 to 2000. Aboriginal women registered with the Department of Indian and Northern Development (DIAND) were linked to a personal health number. Low socioeconomic status was defined as either receiving subsidization for the Alberta Health Care Insurance premium or receiving welfare. RESULTS: Women registered with DIAND and women receiving subsidy or welfare were younger, more often unmarried, smoked more, consumed more alcohol, and abused more illicit drugs than other women in Alberta during the time period studied. Fewer women registered with DIAND and women receiving subsidy or welfare had physician prenatal visits, attended prenatal classes, had forceps or vacuum deliveries, and more of these women frequently had gestation ages less than 37 weeks. Women registered with DIAND had more deliveries in smaller, non-metropolitan facilities; and more of these women delivered outside their region of residence; more had longer lengths of hospital stay; more mothers and neonates were re-admitted to hospital within 28 days of discharge after delivery; fewer delivered small for gestational age neonates; fewer delivered neonates with birth weight less than 2500 g, but more delivered neonates with birth weight greater than 4000 g. There were fewer Caesarean sections in women registered with DIAND (OR = 0.84, 95% CI 0.76-0.93) and in women receiving subsidy or welfare (OR = 0.88, 95% CI 0.82-0.93). CONCLUSION: Women receiving subsidy or welfare and women registered with DIAND had many demographic similarities and generally had worse maternal and neonatal outcomes than other women in Alberta. Medical system interaction may be different for these two groups of women than it is for other women in Alberta.

Adolescent↗
PubMed2002

Cost analysis of ongoing care of patients with end-stage renal disease: the impact of dialysis modality and dialysis access.

BACKGROUND: Care of patients with end-stage renal disease (ESRD) is important and resource intense. To enable ESRD programs to develop strategies for more cost-efficient care, an accurate estimate of the cost of caring for patients with ESRD is needed. METHODS: The objective of our study is to develop an updated and accurate itemized description of costs and resources required to treat patients with ESRD on dialysis therapy and contrast differences in resources required for various dialysis modalities. One hundred sixty-six patients who had been on dialysis therapy for longer than 6 months and agreed to enrollment were followed up prospectively for 1 year. Detailed information on baseline patient characteristics, including comorbidity, was collected. Costs considered included those related to outpatient dialysis care, inpatient care, outpatient nondialysis care, and physician claims. We also estimated separately the cost of maintaining the dialysis access. RESULTS: Overall annual cost of care for in-center, satellite, and home/self-care hemodialysis and peritoneal dialysis were US $51,252 (95% confidence interval [CI], 47,680 to 54,824), $42,057 (95% CI, 39,523 to 44,592), $29,961 (95% CI, 21,252 to 38,670), and $26,959 (95% CI, 23,500 to 30,416), respectively (P < 0.001). After adjustment for the effect of other important predictors of cost, such as comorbidity, these differences persisted. Among patients treated with hemodialysis, the cost of vascular access-related care was lower by more than fivefold for patients who began the study period with a functioning native arteriovenous fistula compared with those treated with a permanent catheter or synthetic graft (P < 0.001). CONCLUSION: To maximize the efficiency with which care is provided to patients with ESRD, dialysis programs should encourage the use of home/self-care hemodialysis and peritoneal dialysis.

Adult↗
PubMed2002

Regulation of eosinophil-active cytokine production from human cord blood-derived mast cells.

Human mast cells are multifunctional tissue-dwelling cells that play a crucial role in eosinophil-dependent disorders, such as asthma and parasitic diseases, by the secretion of eosinophil-active mediators. Mast cell-derived cytokines, generated in response to cross-linking of the high-affinity IgE receptor, can regulate eosinophil activation, survival, and chemotaxis. In this study, mast cells generated from human cord blood progenitors (stem cells) were studied for eosinophil-active inflammatory cytokine expression. Cord blood-derived mast cells (CBDMC) expressed typical intracellular scroll granules and microvilli-like structures on their cell surfaces, demonstrated the presence of tryptase, and elaborated prostaglandin D2 (PGD2) after cross-linkage of the high-affinity receptor for IgE (FcepsilonRI). CBDMC expressed tumor necrosis factor-alpha (TNF-alpha) and the eosinophil-active growth factors, interleukin-5 (IL-5) and granulocyte-macrophage colony-stimulating factor (GM-CSF) after activation. (IL-1beta greatly enhanced IgE-dependent production of these cytokines in response to FcepsilonRI cross-linkage, suggesting a role for bystander/phagocytic cells in modulating mast cell function. In contrast, interferon-alpha (IFN-alpha) inhibited IL-5 and GM-CSF generation, and the glucocorticoid, dexamethasone (Dex), inhibited production of IL-5 and GM-CSF from CBDMC. A macrophage-mast cell-eosinophil axis may exist in vivo that may be susceptible to pharmacologic manipulation.

Cells, Cultured↗
PubMed2002

The association between heart rate and in-hospital mortality after coronary artery bypass graft surgery.

UNLABELLED: Avoidance of tachycardia is a commonly described goal for anesthetic management during coronary artery bypass graft (CABG) surgery. However, an association between increased intraoperative heart rate and mortality has not been described. We conducted an observational study to evaluate the association between preinduction heart rate (heart rate upon arrival to the operating room) and in-hospital mortality during CABG surgery. Data were collected on 5934 CABG patients. Fifteen percent of patients had an increased preinduction heart rate > or =80 bpm. Crude mortality was significantly more frequent among patients with increased preinduction heart rate (P(trend) = 0.002). After adjustment for baseline differences among patients, preinduction heart rate > or =80 bpm remained associated with increased mortality (P(trend) < 0.001). The increased heart rate may be a cause of the observed mortality. Alternatively, faster heart rate may be either a marker of patients with irreversible myocardial damage, or a marker of patients with limited cardiac reserve at risk for further injury. Lastly, faster heart rate may be a marker for under-use of beta-adrenergic blockade. Because the use of preoperative beta-adrenergic blockade in CABG patients is associated with improved in-hospital survival, further investigation concerning the effect of intraoperative treatment of increased heart rate with beta-adrenergic blockers on mortality after CABG surgery is warranted. IMPLICATIONS: We conducted an observational study to evaluate the association between heart rate upon arrival to the operating room (preinduction heart rate) and in-hospital mortality during coronary artery bypass graft surgery. After adjustment for baseline differences among patients, preinduction heart rate > or =80 bpm was associated with an increased in-hospital mortality after coronary artery bypass graft surgery.

Adrenergic beta-Antagonists↗
PubMed2002

Intraparenchymal tension pneumatocele complicating frontal sinus osteoma: case report.

OBJECTIVE AND IMPORTANCE: A relatively rare condition of intraparenchymal tension pneumatocele secondary to a frontal sinus osteoma eroding posteriorly and breaching dura mater is described. The scanty body of literature on this subject is briefly summarized, and the importance of this condition as a result of its life-threatening but readily treatable intracranial mass effect is outlined. CLINICAL PRESENTATION: The patient presented with acute deterioration in conscious state and lateralizing signs from the mass effect of gas under tension. Two weeks earlier, he had experienced vague and subtle changes in personality noticeable only to his family. INTERVENTION: The patient was cured by a frontal craniotomy, partial excision of the osteoma, and suture repair of the dural defect after evacuation of the pressurized air cavity. CONCLUSION: This rare condition should be urgently treated in the event of acute deterioration. To prevent a life-threatening situation from arising, elective surgery should be considered for patients known to have air sinus osteomas that are at risk of erosion into the cranial cavity.

Craniotomy↗
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↗