Search PubMed⌕ Search

Biomedical subjects

J Anderson

Publications and source records attributed to J Anderson.

At least 325 records · Page 18Linked to original sources
PubMed1996

Factors associated with choosing a primary care career.

The factors influencing the career choices of medical students need to be understood so that the proportion of physicians entering primary care-defined as family practice, general internal medicine, general pediatrics, and general obstetrics and gynecology-can be increased. We sent a questionnaire to 474 University of California, San Diego (UCSD), School of Medicine alumni (classes of 1974, 1978, 1982, 1986, and 1990) inquiring about demographics, personal and medical school factors, and level of debt. A total of 351 alumni responded (74% response rate), and 327 of them were engaged in direct patient care (38% in primary care). Respondents who were older, female, an underrepresented minority, from a rural background, and who chose their specialty before medical school were significantly more likely to enter primary care. The primary care group was influenced by factors unrelated to the medical school environment, such as personal social values, whereas the top 3 factors rated by the non-primary care group were directly related to school environment. Many of the respondents in primary care reported that the environment at UCSD was antagonistic toward primary care. From 1974 to 1990, more students had debt and their total debt increased, although debt had little or no influence on specialty choice.

Adult↗
PubMed1996

Endovascular management of vertebral arteriovenous fistulas: the Toronto experience.

OBJECTIVE: This study was designed to evaluate the effectiveness of the endovascular management under angiographic control of vertebral arteriovenous fistulas (AVF). DESIGN: The study included a retrospective chart review. METHOD: Of the eight patients with AVF (2 traumatic, 6 spontaneous) referred to the interventional neuroradiology group at the Toronto Hospital between May 1986 and August 1994, endovascular embolization was attempted in six cases. RESULTS: All cases were successful, with no residual fistula flow, mortality, or morbidity. CONCLUSIONS: Vertebral AVFs are rare; therefore, most centres have had limited experience with their management. Endovascular management has proven to be less difficult and to have less morbidity than surgical management in these cases.

Adolescent↗
PubMed1996

Ethnic differences in women with HIV infection in Britain and Ireland. The study group for the mrc collaborative study of HIV infection in women.

OBJECTIVE: To examine ethnic differences in the socio-epidemiological and clinical characteristics of a cohort of women with HIV infection in Britain and Ireland. DESIGN AND METHODS: Analysis of baseline data (ethnic group, sexual history, likely route of HIV infection, reasons for HIV testing and first AIDS-defining disease) from 400 women with HIV infection recruited into a cohort study from 15 genitourinary medicine/HIV clinics in Britain and Ireland. RESULTS: Sixty-five per cent of women were white and 29% black African. Their median number of lifetime sexual partners was seven and three, respectively (P < 0.001). Ninety-three per cent of black African and 43% of white women were probably infected through sexual intercourse. Injecting drug use was the most likely route of infection in 55% of white women, but none of the black African women. Perceived risk (33%) or investigation of symptoms (26%) were the most common reasons for HIV testing. Seven per cent of white women and 16% of black African women (P < 0.001) had AIDS when HIV infection was diagnosed. The distribution of first AIDS-defining diagnoses differed (P = 0.001) by ethnic group. For white women, the most common disease was Pneumocystis carinii pneumonia; for black African women it was pulmonary tuberculosis. CONCLUSION: There are important differences between black African and white women in sexual history and route of transmission, disease stage at diagnosis and pattern of AIDS-defining diseases.

AIDS Serodiagnosis↗
PubMed1995

Numbers of preceding nontargets differentially affect responses to targets in normal volunteers and patients with schizophrenia: a study of event-related potentials.

This event-related potential study systematically varied the number of nontargets (1, 3, 5, 7, 9) preceding the target tone in an oddball experiment and examined the effect of this on N2, P3, and reaction time measures in schizophrenic patients and normal volunteers. Schizophrenic patients were found to have reduced P3 amplitudes, but this reduction was restricted to series when the targets followed an intermediate number (3-7) of nontargets, and not when targets followed a short (1) or long series (9) of nontargets. Although other interpretations of this finding are possible, the pattern of results could be explained by the hypothesis that the refractory period governing the generation of the P3 component was prolonged in schizophrenia.

Adult↗
PubMed1995

Regional differentiation of cortical activity in schizophrenia: a complementary approach to conventional analysis of regional cerebral blood flow.

This study examines an alternative to a narrow locus-of-dysfunction cortical pathophysiology in schizophrenia, which in turn suggests a modified approach to the analysis of data from regional cerebral blood flow studies. The results provide qualified support for a model of impaired differentiation of cortical activity in schizophrenia. As an index of the differentiation of cortical fields, regional gradients of cortical blood flow were examined. Medicated patients (n = 15) failed to show the differentiation of networks in frontal areas during a verbal memory recognition task observed in normal comparison subjects (n = 15). Unmedicated patients (n = 15) at rest tended to lose normal lateralization and had increased gradients in the right frontal area compared with normal comparison subjects.

Adult↗
PubMed1995

Maximum variance of late component event related potentials (190-240 ms) in unmedicated schizophrenic patients.

The averaging of individual late component event related potential (ERP) responses, particularly P300, has revealed significant differences between schizophrenic patients and normal subjects. However, the averaging process removes the variability of the individual epochs that constitute that average. The response-variance-curve (RVC) method quantifies the variability of the individual epochs and allows examinations of windows of maximum variance. In this study, we examine the complementary nature of the RVC method to the traditional averaging approach. The averaged N200 and P300 ERP components differed significantly between the schizophrenic and normal groups, but not between the unmedicated and medicated schizophrenic patients. The RVC measure, on the other hand, revealed systematic differences in variability, maximal between 190 and 240 ms, between the unmedicated and medicated schizophrenic patients. The RVC measure therefore provides a focused time frame in which to examine dysfunctions in information processing and macroscopic scale changes in brain function due to medication.

Acoustic Stimulation↗
PubMed1995

Event related response variability in schizophrenia: effect of intratrial target subsets.

The response-variance-curve (RVC) method quantifies the variability of the individual epochs that constitute the average event related potential (ERP), providing complementary information to that offered by ERPs. Numerous studies have found that average ERP late components of an auditory "oddball" paradigm can differentiate schizophrenic patients from normal subjects. Our previous study of the RVC measure revealed significant differences between medicated and unmedicated schizophrenic patients in the maximum ERP variability from 190 to 240 ms. In the present study of unmedicated schizophrenic patients and normal control subjects, we examined the influence of intertarget intervals (generated by pseudorandom stimulus sequences in an auditory oddball paradigm) on the intratrial effects of ERP variability measured by the RVC. The ERPs of unmedicated schizophrenic patients were characterized by an instability in a latency window corresponding to the N200 component. The effect was particularly large at an intertarget interval of 7.8 s and was significantly reduced on either side of this intertarget interval.

Acoustic Stimulation↗
PubMed1995

Truncated biphasic pulses for transthoracic defibrillation.

BACKGROUND: Early defibrillation is the single most important factor for improving out-of-hospital ventricular fibrillation resuscitation rates. To achieve the earlier response times required for survival, typically < 6 minutes from time of collapse, it will be necessary to equip a far wider network of first responders (firefighters, police, and other individuals with responsibility for public safety) with small, lightweight, and inexpensive automatic external defibrillators (AEDs). An important step in reducing the size and cost of AEDs will be to improve defibrillation efficacy. Because biphasic waveform defibrillation has had a favorable impact on implantable cardioverter-defibrillators (ICDs), there are reasons to believe that biphasic waveforms would also improve transthoracic defibrillators. Our purpose, therefore, was to examine the efficacy of two different low-energy biphasic truncated waveforms referenced to a standard damped sine waveform for transthoracic defibrillation in humans. METHODS AND RESULTS: We prospectively and randomly compared the transthoracic defibrillation efficacy of two different truncated biphasic waveforms, 115 J (70 microF) and 130 J (105 microF), with that of a standard 200-J (36-microF, 28-mH) damped sine wave pulse using right anterior and left lateral thoracic pads (R2 Medical Systems) in 30 cardiac arrest survivors during transvenous ICD surgery. The right anterior patch electrode was used as the cathode and the left lateral thoracic pad as the anode. Transthoracic ventricular defibrillation rescue shocks were tested after a failed transvenous defibrillation shock delivered in the course of ICD testing. Each of the three different rescue shocks was tested in random order in each patient. All shocks were delivered at end expiration. The investigators responsible for determining transthoracic shock efficacy were blinded throughout the study to the transthoracic rescue waveform used. A total of 33 patients were considered for study, but three patients failed to satisfy all entry criteria or did not have a sufficient number of ventricular fibrillation inductions to allow for testing of all three waveforms. Percent efficacy for the three waveforms was then compared in the 30 patients who satisfied entry criteria and completed the protocol. The study population had a mean age of 61 +/- 11 years, with 22 (73%) being men. The mean left ventricular ejection fraction was 0.39 +/- 0.14. Coronary artery disease was present in 22 (73%). The 115-J (70-microF) biphasic pulse, the 130-J (105-microF) biphasic pulse, and the 200-J (36-microF, 28-mH) damped sine wave pulse were equally effective, resulting in a 97% first-shock ventricular defibrillation efficacy rate. Each waveform failed to defibrillate once, with each waveform failing in a different patient. CONCLUSIONS: The results of this study suggest that biphasic truncated transthoracic shocks of low energy (115 and 130 J) are as effective as 200-J damped sine wave shocks used in standard transthoracic defibrillators. This finding may contribute significantly to the miniaturization and cost reduction of transthoracic defibrillators, which could enable the development of a new generation of AEDs appropriate for an expanded group of out-of-hospital first responders and, eventually, layperson use.

Adult↗
PubMed1995

The prevalence and characteristics of fibromyalgia in the general population.

OBJECTIVE: To determine the prevalence and characteristics of fibromyalgia in the general population. METHODS: A random sample of 3,006 persons in Wichita, KS, were characterized according to the presence of no pain, non-widespread pain, and widespread pain. A subsample of 391 persons, including 193 with widespread pain, were examined and interviewed in detail. RESULTS: The prevalence of fibromyalgia was 2.0% (95% confidence interval [95% CI] 1.4, 2.7) for both sexes, 3.4% (95% CI 2.3, 4.6) for women, and 0.5% (95% CI 0.0, 1.0) for men. The prevalence of the syndrome increased with age, with highest values attained between 60 and 79 years (> 7.0% in women). Demographic, psychological, dolorimetry, and symptom factors were associated with fibromyalgia. CONCLUSION: Fibromyalgia is common in the population, and occurs often in older persons. Characteristic features of fibromyalgia--pain threshold and symptoms--are similar in community and clinic populations, but overall severity, pain, and functional disability are more severe in the clinic population.

Adult↗
PubMed1995

Prediction of cardiac death in patients with a very low ejection fraction after myocardial infarction: a Cardiac Arrhythmia Suppression Trial (CAST) study.

The Cardiac Arrhythmia Suppression Trial (CAST) database was analyzed with a Cox proportional hazards regression model to predict the mortality of patients with very poor left ventricular systolic function (ejection fraction < or = .20). Predictors of total death or cardiac arrest were (relative risk), QRS duration (1.10/10 msec increase), coronary artery bypass grafting (0.38), basal heart rate (1.26/10 min-1 increase), diastolic blood pressure (0.79/10 mm Hg increase), diabetes mellitus (1.59), EF (0.94/1 U increase), and ease of suppression (the ability to suppress ambient ventricular ectopy on the lowest dose of the first randomly chosen CAST drug) (0.64). Predictors of arrhythmic death or arrhythmic cardiac arrest included thrombolysis (0.44), coronary artery bypass grafting (0.38), diuretic use (1.71), heart rate (1.21/10 min-1 increase), calcium channel blocker use (1.69), and QRS duration (1.10/10 msec increase). Thus easily measurable clinical and laboratory variables help predict prognosis in this clinically important subgroup. The pathophysiologic basis for and the clinical implications of the ease of ventricular arrhythmia suppression correlating with prognosis requires further study.

Blood Pressure↗
PubMed1995

Intracoronary ultrasound-defined plaque composition: computer-aided plaque characterization and correlation with histologic samples obtained during directional coronary atherectomy.

The ability to classify lesion composition accurately may be important for selecting or guiding interventional therapy and for understanding the pathophysiologic basis of individual lesions. To assess the usefulness of ultrasound in classifying lesions, intracoronary ultrasound images were obtained from 44 atherosclerotic lesions in patients before directional atherectomy. Lesions were classified by visual analysis and by computer-assisted gray-level statistics. Atherectomy samples were evaluated histologically for elastosis and calcium and quantitatively by morphometric analysis for various tissue components. The computer-assisted quantitative classification agreed well with the findings on visual analysis. Visual and computer-assisted quantitative ultrasound images were found to have distinctive histologic features. Lesions with predominantly echogenic plaque had a larger fraction of dense fibrous, elastic, or calcified tissue. Lesions with predominantly echolucent soft plaque had a greater fraction of loose fibrous, smooth-muscle, thrombotic, or necrotic elements. Thus intracoronary ultrasound allows accurate classification of lesion composition in patients.

Atherectomy, Coronary↗
PubMed1995

Mechanical complications after implantation of multiple-lead nonthoracotomy defibrillator systems: implications for management and future system design.

Nonthoracotomy lead system (NTL) implantable cardioverter defibrillators (ICDs) provide excellent protection against sudden death from ventricular tachyarrhythmias. However, these devices have unique mechanical complications and management issues. We reviewed the major complications occurring in 159 patients who underwent attempted implantation of a multilead NTL system. Successful implantation was obtained in 98% of patients. Two-year, all-cause actuarial survival on an intention-to-treat basis was 94%. Major complications occurred in 28 (17.6%) patients over a follow-up period of 21 +/- 10 months. Complications included 11 (6.9%) lead dislodgements, 10 (5.7%) lead fractures in 9 patients, 2 (1.3%) pocket infections, 1 frozen shoulder, 1 right ventricular perforation, 1 pneumothorax, 1 bleed requiring transfusion, 1 thromboembolism, and 1 "twiddle"-induced torsion of leads. Most of the lead dislodgements and fractures were identified by routine x-ray surveillance. Single-lead systems may significantly reduce complication rates in the future and maintain excellent survival rates.

Actuarial Analysis↗
PubMed1995

Classification of single-trial ERP sub-types: application of globally optimal vector quantization using simulated annealing.

Examination of the single trials which are traditionally averaged to form late-component ERPs reveals a number of different sub-types of response. This study introduces an automated and robust approach to objectively classify these ERP sub-types. Auditory oddball ERP (target tones) data were examined in 25 normal subjects. Globally optimal vector quantization using simulated annealing (the "Metropolis algorithm") was employed to determine the natural groupings of the single-trial responses that constitute the average ERP. No prior assumptions about the ERP patterns were imposed. This is the first study to employ a cluster analysis technique with globally optimal properties in ERP research. We demonstrate that, due to the presence of many different undesirable local minima, a globally optimal solution is crucial if the classification of the single-trial ERPs is to reflect their real structure. The results of this study showed that only around 40% of single trials had a morphology which resembled the averaged ERP wave form. The remaining single trials had a response morphology which was different from the average, in terms of the amplitude and latency of the components. Single-trial ERP response sub-types may provide fundamental complementary functional information to the ERP average.

Acoustic Stimulation↗
PubMed1995

Use of cyclophosphamide as a positive control in dominant lethal and micronucleus assays.

Analyses of dominant lethal (DL) mutations and micronuclei (MN) are 2 important and widely used genotoxicity assays to measure drug-induced chromosome damage in germ cells and somatic cells, respectively. Cyclophosphamide (CP) has been widely used as a positive control in the single-dose mouse MN assay; however, its utility as a positive control for the DL assay has not been fully studied. In the present study, CP was tested in both assays under similar experimental conditions and MN seen in somatic tissue (bone marrow) were correlated with DL mutations seen in germinal tissue. In a dose-range finding study, groups of 5 male mice were dosed i.p. daily for 5 days at 0, 30 or 40 mg/kg CP and bone marrow was harvested 24 h later for MN assay. CP induced a dose-related increase (7- and 11-fold over control at 30 and 40 mg/kg) in micronucleated polychromatic erythrocytes (MNPCEs) and decreased %PCEs (to 60% and 54% of controls at 30 and 40 mg/kg, respectively). Based on this, a definitive DL and MN study was conducted using separate groups of 30 male mice at 0 and 40 mg/kg CP with a daily times 5 dosing regimen. For the MN assay, bone marrow was collected 24 h after the last dose from 5 animals and evaluated for MNPCEs and %PCEs. For the DL assay, each male was caged with 2 untreated females per week for 8 weeks to cover the postmeiotic germ cell stages. On day 17 after the initiation of breeding, the females were evaluated for the number of implantation sites and live, dead and resorbed implants. The results indicated that CP induced about a 17-fold increase in MNPCEs and a 46% decrease in PCEs in relation to controls. In the DL assay, CP produced a slight (13%) but statistically significant reduction in fertility index at week 7 of mating. Also, the total number of implants was significantly lower during weeks 1, 2, 3, 6 and 7 and the numbers of dead implants and postimplantation loss (PIL) were increased for weeks 1, 2 and 3 (55%, 71% and 34% PIL, respectively) over controls. These data clearly show that CP produced clastogenicity and some toxicity in both somatic tissue and germinal tissue. It was concluded that a dose of 40 mg/kg CP can be used as a positive control compound in the DL assay and in the multiple-dose marrow MN assay.

Animals↗
PubMed1995

Competitive ELISA for the detection of antibodies against epizootic haemorrhagic disease of deer virus.

A competitive enzyme-linked immunosorbent assay is described for the detection of antibodies against epizootic haemorrhagic disease of deer viruses (EHDV). Test antisera were tested against a guinea-pig antiserum raised against EHDV core particles. The assay detected antibodies to all serotypes of EHDV, but unlike the agar gel immunodiffusion (AGID) test, gave no cross-reactions with antibodies against bluetongue, Palyam and Tilligery viruses. The C-ELISA would be ideal for use in epidemiological surveys since it is suitable for the examination of antisera from all susceptible species without the need for individual species-specific enzyme conjugates.

Animals↗