Biomedical subjects

M E Johnston

Publications and source records attributed to M E Johnston.

At least 19 recordsLinked to original sources

PubMed1992

Depression, problem-solving ability, and problem-solving appraisals.

Behavioral analytic methods were used to create a college student version of the Means Ends Problem Solving Procedure (MEPS). This instrument then was administered with measures of perceived problem-solving ability to depressed and nondepressed students to determine whether differences exist in both problem-solving ability and problem-solving appraisal. Analyses revealed that depressed subjects had more negative expectations and lower appraisals of their problem-solving ability. However, the groups did not differ in terms of the actual quality of their behavioral solutions to interpersonal, intrapersonal, and emotional problem situations. The results are interpreted as support for the role of cognitive factors in depression and problem-solving across a range of problem-solving situations.

Adaptation, Psychological↗

PubMed1992

Performance appraisal of online MEDLINE access routes.

OBJECTIVE: To compare the performance and cost of 11 online MEDLINE systems with MEDLINE at Elhill. DESIGN: Comparative study. SYSTEMS: Eleven online daytime systems commercially available in North America offering the MEDLINE database. MEASURES: Number of relevant citations, number of irrelevant citations, proportion of searches producing no relevant citations and cost per relevant citation were analyzed for each system. Relevance and cost for each system were compared with direct searching of MEDLINE through NLM for librarian and clinician search strategies for 18 clinical questions. The citations retrieved by both strategies were pooled and rated for relevance on a 7-point scale. RESULTS: Numbers of relevant and irrelevant citations and cost per relevant citation were higher for clinician searches than librarian searches, reflecting the higher total number of citations retrieved by the clinician approaches. A lower proportion of clinician searches produced no relevant citations than librarian searches. CONCLUSIONS: Eleven daytime MEDLINE systems performed similarly in terms of retrieval and cost within similar searching groups. Clinicians, however, tended to capture larger overall retrievals resulting in higher numbers of relevant and irrelevant citations than librarians.

CD-ROM↗

PubMed1992

Increases in knowledge and use of information technology by entering medical students at McMaster University in successive annual surveys.

OBJECTIVE: To determine self-reported microcomputer and information technology competency, access, and usage by entering medical students and their perceptions of the need for training in additional applications. DESIGN: Cross-sectional surveys of successive classes. SETTING: McMaster University Faculty of Health Sciences Medical Undergraduate Program, which has a 33-month, problem-based, self-directed learning curriculum and a high applicant-to-student ratio. PARTICIPANTS: Medical school classes entering in 1987, 1988, and 1989. Response rates were 80%, 90%, and 86% respectively. MEASURES: A self-report questionnaire was sent to each student, with up to two follow-up letters to prompt a response. RESULTS: There was a progressive rise in reported information technology access and use for the three years. For the classes starting in 1987, '88, and '89 respectively, computer access was 29%, 49%, and 49% (P < 0.002 for linear trend), and, among those with computer access, modem access was 17%, 29% and 50% (P = 0.012). Self-service MEDLINE use on CD-ROM at the Health Sciences Library was 65%, 75%, and 89% respectively (P < 0.001) for all respondents within the first few months of starting medical school. Over 50% of each class stated they would take courses, if available, on clinical applications software, office management, online searching, filing, and CD-ROM searching. CONCLUSIONS: Half of the most recent entering students already had access to a personal computer and most wished to learn computer applications that would assist them with patient management, and with information access and organization. Medical schools need to address which applications they will teach or make available and how to bring all students to acceptable competency in their use.

Computer Literacy↗

PubMed1992

A critical appraisal of the literature on the effects of computer-based clinical decision support systems on clinician performance and patient outcomes.

OBJECTIVE: To review the evaluations of computer-based clinical decision support systems (CDSS's). DATA SOURCES: The literature collected in the MEDLARS, EMBASE, SCISEARCH and INSPEC databases was searched from 1974 to the present. The reference lists of relevant articles were reviewed as were conference proceedings. STUDY SELECTION: Prospective, controlled studies were included. Studies were rated for methodological quality. DATA EXTRACTION: Study quality was assessed and data on study setting, subjects, method of allocation, and computer system were collected and verified using a structured form. CONCLUSIONS: There is considerable heterogeneity in both systems evaluated and design features of those systems. Future evaluations of CDSS's should focus on methodological issues in order to enhance overall quality of evaluations.

Clinical Medicine↗

PubMed1991

A study to enhance clinical end-user MEDLINE search skills: design and baseline findings.

OBJECTIVE: To determine if a preceptor and timely, individualized feedback improves the performance of physicians in searching MEDLINE using GRATEFUL MED in clinical settings. DESIGN: Randomized controlled trial. SETTING: A 300 bed primary to tertiary care teaching hospital. Computers were installed in wards and clinics of 6 major clinical services, and the emergency room, intensive care and neonatal intensive care units. SUBJECTS: All physicians and physicians-in-training from the departments of Medicine, Family Medicine, Surgery, Psychiatry, Pediatrics, and Obstetrics and Gynecology were included if they made patient care decisions for at least 8 weeks during the study period. INTERVENTION: All participants were given a 1-hour training class and 1 hour of individualized searching with 1 of the 2 study librarians. After training, participants were randomized to a control group who received no further intervention or to an intervention group in which each person chose a clinical preceptor experienced in MEDLINE searching and received individualized feedback by a study librarian on their first 10 searches, indicating search quality and providing suggestions for improvement. Feedback was mailed the first week day after the search was done. MAIN MEASURES: Baseline characteristics by study group, department and level of training, study participation rates, and searching rates. MAIN RESULTS: 308 of 392 eligible physicians joined the study. Participation was almost 80% with some variation by department and level of training. Excellent balance in the baseline characteristics was achieved for the 2 groups, as well as for the number who did first searches. Intervention group participants searched MEDLINE more often than did controls (3.5 searches per month vs 2.5 per month for controls, P = 0.046). The recall and precision for first searches for both groups was significantly less than that of librarians. The analysis of study data will be completed by September 1991. CONCLUSIONS: Clinicians are willing to do self-service searching of MEDLINE in clinical settings but their precision and recall are less than a trained librarian at baseline. Search skills enhancements are needed and the effect of feedback and preceptors is being tested. SOURCE OF FUNDING: U.S. National Library of Medicine and Ontario Ministry of Health.

Computer User Training↗

PubMed1990

Adenosine transport systems on dissociated brain cells from mouse, guinea-pig, and rat.

The kinetics and sodium dependence of adenosine transport were determined using an inhibitor-stop method on dissociated cell body preparations obtained from mouse, guinea-pig and rat brain. Transport affinity (KT) values for the high affinity adenosine transport systems (KT(H] were significantly different between these three species; mean +/- SEM values were 0.34 +/- 0.1 in mouse, 0.9 +/- 0.2 in rat, and 1.5 +/- 0.5 microM in guinea-pig. The KT values for the low affinity transport system (KT(L) were not different between the three species. Brain cells from rat displayed a significantly greater maximal capacity to accumulate [3H]adenosine (Vmax) than did mouse or guinea-pig for the high affinity system, or than did mouse for the low affinity system. When sodium chloride was replaced in the transport medium with choline chloride, the KT(H) values for guinea-pig and rat were both increased by approximately 100%; only in rat did the change reach statistical significance. The sodium-dependence of adenosine transport in mouse brain was clearly absent. The differences between KT(H) values in mouse and those in guinea-pig or rat were accentuated in the absence of sodium. The differences in kinetic values, ionic requirements, and pharmacological characteristics between adenosine transporters in CNS tissues of mouse, guinea-pig and rat may help account for some of the variability noted among species in terms of their physiological responses to adenosine.

Adenosine↗

PubMed1990

Effect of select menhaden fish meal in starter diets for pigs.

Two trials were conducted to evaluate a select menhaden fish meal (SMFM) as a protein source in starter diets for 390, 3-wk-old weaned pigs. Initial weights averaged 4.8 and 5.5 kg in Trials 1 and 2, and trials were conducted for 5 and 4 wk, respectively. Diets in Trial 1 were formulated by substituting levels of 0, 4, 8, 12, 16 or 20% SMFM for soybean meal plus corn on a protein basis. The 20% fish meal diet contained no soybean meal; all diets contained between 19.8 and 20.2% CP, between 1.34 and 1.40% lysine and 25% dried whey. Replacement of soy protein with fish meal elicited a quadratic improvement (P = .01) in cumulative ADG and average daily feed intake (ADFI) by the end of wk 5. The diet containing 8% SMFM resulted in the maximum observed ADG; however, the maximum ADFI occurred in pigs fed the diet containing 12% SMFM. Breakpoint analysis indicated that 4.5 and 9.3% SMFM maximized ADG and ADFI, respectively. Addition of SMFM did not affect efficiency of feed utilization (F/G). In Trial 2, a 2 X 3 factorial with two levels of dried whey (10 or 20%) and three levels of SMFM (0, 4 or 8%), a SMFM X dried whey interaction (P less than .05) was observed for cumulative ADG and F/G by the of wk 4 with greater benefit from SMFM with 10% than with 20% dried whey.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1989

HLA class I-related impairment in IL-2 production and lymphocyte response to microbial antigens in reactive arthritis.

The contribution of certain Gram-negative bacteria and host HLA class I Ag to the development of reactive arthritis (ReA)3 has strong epidemiologic support but the pathogenesis of the arthritis is unknown. An outbreak of Salmonella typhimurium afforded the opportunity to compare the immune response to the organism between those who developed ReA (ReA+, n = 11) with those who did not (ReA-, n = 12). Of the 11 ReA+ patients, 4 were B27-positive and 6 were B7-positive; of the ReA- patients none was B27- or B7-positive. The causative pathogen S. typhimurium phage 22 was used to examine PBL proliferation by [3H]thymidine incorporation. Impairment in lymphocyte response to S. typhimurium in ReA+ compared with ReA- was demonstrated by: i) lower stimulation index (1.9 +/- 0.3 for ReA+, 5.7 +/- 0.6 for ReA-, p less than 0.01); ii) lower in vitro Ig production; and iii) lower Ag-induced IL-2 production. Mixing experiments did not demonstrate a soluble suppressor factor in ReA+ supernatants. Thus, after infection with S. typhimurium there is an impairment in cellular immunity that has correlates in immunogenetic and clinical features of the infected population.

Antibodies, Bacterial↗

PubMed1989

Sodium-dependent uptake of nucleosides by dissociated brain cells from the rat.

Sodium-dependent 3H-labeled nucleoside transport was studied using a mixed population of dissociated brain cells from adult rats. The accumulation of [3H]adenosine during brief (15-s) incubation periods was significantly greater in the presence of 110 mM Na+ than in its absence. This occurred at substrate concentrations that ranged from 0.25 to 100 microM. Similar findings were observed for the rapid accumulation of [3H]uridine. Kinetically, the rapid accumulation of [3H]adenosine in both the absence and the presence of Na+ was best described by a two-component system. In the presence of Na+, the KT and Vmax values for the high-affinity affinity component were 0.9 microM and 8.9 pmol/mg of protein/15 s, and those for the low-affinity component were 313 microM and 3,428 pmol/mg of protein/15 s, respectively. In the absence of Na+, the KT value for the high-affinity component was significantly higher (1.8 microM). [3H]Uridine accumulation was best described kinetically by a one-component system that in the presence of Na+ had KT and Vmax values of 1.0 mM and 2.6 nmol/mg of protein/15 s, respectively. As was found for [3H]adenosine, in the absence of Na+, the KT value was significantly higher (1.8 mM). The sodium-dependent transport of [3H]adenosine was inhibitable by ouabain and 2,4-dinitrophenol. Of the three nucleoside transport inhibitors tested, only nitrobenzylthioninosine demonstrated high affinity and selectivity in blocking the sodium component. Thus, high-affinity sodium-dependent nucleoside transport systems, in addition to facilitated diffusion systems, exist on brain cells from adult rats.

Adenosine↗

PubMed1988

Postdysenteric reactive arthritis. A clinical and immunogenetic study following an outbreak of salmonellosis.

Following an outbreak of foodborne gastroenteritis caused by Salmonella typhimurium, questionnaires were sent to affected individuals and then to the family physicians of any who experienced extra-enteric complications. Of 260 individuals infected with S typhimurium for whom adequate data were obtained, 19 patients developed joint disease (7.3%). All were men; the mean age +/- SD was 39.3 +/- 1.6 years. Among the 16 patients for whom this information was available, the interval from the onset of diarrhea to the onset of joint pain was less than 7 days in 7, 8-21 days in 2, and greater than 21 days in 7. There was a significantly longer duration of diarrhea in those patients with joint disease (mean +/- SEM 15.2 +/- 2.6 days) than in those without complications (10.0 +/- 1.1 days) (P less than 0.01). The joint disease was monarticular in 3 patients and polyarticular in 16. The joints most commonly affected were the elbow (47%), wrist (47%), knee (42%), low back (32%), and shoulder (32%). Six of the 19 patients had at least 1 extraarticular feature: ocular (5 patients), mucosal (1 patient), urethral (2 patients), or cutaneous (1 patient). Of these 19 patients, 11 were located and agreed to HLA typing. Four were positive for HLA-B27, 6 were HLA-B7 positive, and 1 had HLA-Bw60. Of the 4 B27 positive patients, 3 were DR1 positive; of the 6 B7 positive patients, 5 were DR2 positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Pharmacological characterization of rapidly accumulated adenosine by dissociated brain cells from adult rat.

Mechanically dissociated brain cells from adult rats were used to study biochemically and pharmacologically their capacity to accumulate rapidly [3H]adenosine. The assay, which used an inhibitor-stop method to prevent further uptake into cells, was characterized with respect to protein and optimal substrate concentrations, and incubation times that ranged from 5 to 180 s. The accumulation of [3H]adenosine using 15-s incubation periods, conditions under which less than 10% of accumulated [3H]adenosine was metabolized, was best described kinetically by a two-component system with Km and Vmax values for the high-affinity component of 0.8 microM and 6.2 pmol/mg protein/15 s and for the low-affinity component 259 microM and 2,217 pmol/mg protein/15 s, respectively. The potencies with which nucleosides, adenosine deaminase resistant adenosine receptor agonists, and nucleoside uptake inhibitors competed for these uptake components were determined. Of the nucleosides examined, adenosine was the "preferred" substrate for the uptake site. The Ki value of adenosine for the high-affinity component was 10.7 microM. Inosine and uridine competed for a single lower affinity uptake system: Ki values were 142 and 696 microM, respectively. Nucleoside uptake inhibitors--nitrobenzylthioinosine, dipyridamole, and dilazep--were the most potent inhibitors of [3H]adenosine accumulation tested: the Ki values for the high-affinity system were 0.11, 1.3, and 570 nM, respectively. The adenosine analogs S-phenylisopropyladenosine, R-phenylisopropyladenosine, and cyclohexyladenosine inhibited the high-affinity component with Ki values of 2.3, 9.3, and 14.5 microM, respectively. N-Ethylcarboxamidoadenosine competed for a single lower affinity uptake system: Ki, 292 microM.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗

PubMed1988

Clinical significance of common eye changes in older patients.

The limbus is often affected by degenerative lesions, many associated with the aging process. Some degenerations may cause irritation, discomfort, and poor vision, thus requiring ophthalmological treatment, while a few require systemic evaluation and treatment. As the limbus is also subject to neoplasms and inflammatory processes, any limbal lesion whose identity is less than obvious should prompt an ophthalmologic consultation.

Aged↗

PubMed1988

Successful treatment of the ocular ischemic syndrome with panretinal photocoagulation and cerebrovascular surgery.

The ocular ischemic syndrome is a manifestation of chronic vascular insufficiency. The natural history is for progressive visual loss. The authors describe 12 patients (13 eyes) who presented with at least one asymmetric ocular finding, including midperipheral dot and blot hemorrhages (hypoperfusion retinopathy) (in 8), iris neovascularization (in 7), neovascular glaucoma (in 3) and vitreous hemorrhage (in 1). Cerebral angiography revealed stenosis or occlusion of the ipsilateral carotid artery in all cases. The treatment was panretinal photocoagulation (in four cases), cerebrovascular surgery (in three) or both (in six). All but one patient showed stabilization of visual acuity (20/60 or better in nine cases) and regression of proliferative retinopathy and of iris neovascularization. The results underline the importance of early recognition and treatment of the ocular ischemic syndrome.

Cerebral Angiography↗

PubMed1987

Analysis of serum and synovial fluid IgA in Reiter's syndrome and reactive arthritis.

The presumed antecedent infection which precedes Reiter's syndrome and reactive arthritis is frequently across a mucosal surface, and IgA immune responses may play a role in this process. Twelve of 29 patients with these conditions demonstrated elevation in serum IgA levels, and serum IgA levels in the postdysentery group (mean 3.21 g/liter +/- 1.27) were higher (P less than 0.01) than those in the posturethritis group (mean 2.40 g/liter +/- 0.80). In 10 of the 12 patients, IgA was the only immunoglobulin increased. There was no evidence of activation of complement in serum or synovial fluid. Using a complement-dependent assay, we were unable to demonstrate circulating IgA immune complexes. Sucrose density gradient ultracentrifugation analysis was used to assess IgA immune complexes in a non-complement-dependent manner. IgA of 11s was in fact demonstrated by this technique but appeared to be polymeric IgA on the basis of specific binding of secretory component and resistance to acid dissociation. IgA rheumatoid factor was not present. Synovial fluid revealed levels of polymeric IgA higher (mean 56.7% +/- 12.9) than did serum (23.7% +/- 13.9, P less than 0.001) despite higher levels of total IgA in serum than in synovial fluid (synovial fluid:serum ratio of IgA, mean 0.53 +/- 0.11). Although elevation in serum IgA in postdysenteric arthropathies suggests mucosal acquisition of antigen, the study does not implicate IgA circulating immune complexes in the pathogenesis of these diseases.

Antigen-Antibody Complex↗

PubMed1987

Immunochemical analysis of immune response to Chlamydia trachomatis in Reiter's syndrome and nonspecific urethritis.

Chlamydia trachomatis (Ct) has been proposed as a causative agent in Reiter's syndrome (RS) when an infection occurs in a susceptible host. To assess whether this susceptibility is reflected in a characteristic humoral immune response we compared patients with complicated (RS) and uncomplicated courses of nonspecific urethritis (NSU). Geometric mean titres of antibodies to C. trachomatis by immunofluorescence were 89.6 for RS, 80.0 for NSU and 16.0 for normals. 125I-Protein A probing of immunoblotted antigens of C. trachomatis revealed no band unique to RS. 125I-anti-IgA probing of immunoblots demonstrated reactivity with the 59,000 dalton antigen in 11/11 RS and 2/6 NSU. The major outer membrane protein of C. trachomatis (40,000 daltons) bound immunoglobulin nonspecifically. There was no clearly differentiating feature between HLA-B27-positive and B27-negative RS. One sequentially studied patient revealed an augmentation in synovial fluid IgA reactivity during the course of disease. No pattern of humoral immune response to C. trachomatis could be regarded as specific for RS nor for HLA B27-positivity. The study did not identify a Reiter's-specific antigen in C. trachomatis but demonstrates the usefulness of applying blotting techniques to population studies of HLA modulation of immune response to infectious agents.

Adult↗

PubMed1986

Hypertension control in two Canadian communities: evidence for better treatment and overlabelling.

We evaluated the prevalence and control of hypertension in two Canadian cities without university medical centre facilities. A stratified multistage probability sample was selected, and we interviewed 6258 adults between the ages of 30 and 69 inclusive. Blood pressure measurements were obtained during home interviews. Up to two further visits were made to people with untreated blood pressure elevation. By a diagnostic criterion of 90 mmHg, the hypertension prevalence was 114/1000. Six per cent of the hypertensives were undetected, 6% detected but untreated, 17% treated but uncontrolled and 70% were being treated and controlled. Control was better in females and older subjects. These findings show no disadvantages to hypertensives living away from university medical centres. We found a hypertension prevalence of 143/1000 among people who reported being diagnosed as hypertensive but who had normal blood pressure while not on medication. These results suggest a problem with over-labelling of hypertensives.

Adult↗

PubMed1986

Arthritis, vasculitis, and cryoglobulinemia associated with relapsing hepatitis A virus infection.

Hepatitis A virus, unlike hepatitis B virus, has rarely been associated with extrahepatic features. Two patients developed relapsing hepatitis A complicated by arthritis in both cases and cutaneous vasculitis in one. Both patients had cryoglobulinemia, with cryocrit values of 4.3% and 8.6%. Serologic studies showed that the cryoglobulin consisted of polyclonal IgM and IgG. The washed cryoglobulin was analyzed by sucrose density gradient ultracentrifugation under neutral (pH 7.4) and acidic (pH 2.8) conditions. Enzyme-linked immunosorbent assay techniques were used to characterize the native and dissociated cryoglobulin. The cryoglobulin contained acid-dissociable IgG complexes greater than 19S, and high molecular weight rheumatoid factors of both IgG and IgM isotypes that could be dissociated to 7S and 19S forms, respectively. Dissociation of the cryoglobulin augmented 7S anti-hepatitis A virus IgG 2.27-fold, but augmented total 7S IgG only 1.12-fold, suggesting enrichment of antiviral antibody in the cryoglobulin.

Adult↗

PubMed1986

Molecular mimicry in Reiter's syndrome: cytotoxicity and ELISA studies of HLA-microbial relationships.

The pathogenic links between HLA antigens, certain bacterial infections and arthritis have not yet been characterized. The hypothesis of cross-reactivity between HLA B27, the marker of disease susceptibility for these disorders, and the provocative microorganism has been suggested by studies of Klebsiella and ankylosing spondylitis. The present study examines the possibility of molecular mimicry between HLA B27 and two organisms implicated more directly in reactive arthritis, Yersinia enterocolitica and Chlamydia trachomatis. Antibodies against these organisms were obtained both from patients and from antisera raised in rabbits. Neither source of antibacterial antibody was specifically cytotoxic for HLA B27-positive lymphocytes, even when the target cells were derived from patients with recent infections due to these organisms. In addition, monoclonal antibodies against HLA B27 (M1 and M2) showed no reactivity with antigens from these organisms in an ELISA system. These data do not support the notion of molecular mimicry as being the basis of immunogenetic susceptibility to reactive arthritis and Reiter's syndrome following infections with Y. enterocolitica and C. trachomatis.

Antigens, Bacterial↗