Quantitative assessment of myocardial scar heterogeneity using cardiovascular magnetic resonance texture analysis to risk stratify patients post-myocardial infarction.

AIM: To determine whether heterogeneity of cardiac scar, as assessed by cardiovascular magnetic resonance (CMR) texture analysis, may provide insight into better risk stratification for patients with previous myocardial infarction (MI). MATERIALS AND METHODS: Patients with previous MI (n=76) were followed for a median of 371.5 days after late gadolinium enhancement (LGE) CMR. The primary endpoint was a composite of ventricular tachycardia, ventricular fibrillation, or unexplained syncope. Areas of LGE were identified and manually segmented on a short-axis projection. The characteristics of the scar heterogeneity were evaluated via CMR texture analysis. This is a filtration-histogram technique, where images are filtered using the Laplacian of a Gaussian filter to extract features different sizes (2-6 mm in radius) corresponding to fine, medium, and coarse texture scales followed by a quantification step using histogram analysis (skewness and kurtosis). RESULTS: Patients suffering arrhythmic events during the follow-up period demonstrated significantly higher kurtosis (coarse-scale, p=0.005) and lower skewness (fine-scale, p=0.046) compared to those suffering no arrhythmic events. Furthermore, Kaplan-Meier analysis showed significantly higher coarse kurtosis (p=0.004), and lower fine skewness (p=0.035) were able to predict increased incidence of ventricular arrhythmic events. CONCLUSIONS: In this pilot study, indices of texture analysis reflecting textural heterogeneity were significantly associated with a greater incidence of arrhythmic events. Further work is required to delineate the role of texture analysis techniques in risk stratification post-MI.

Decreased GABAA receptors and benzodiazepine binding sites in the anterior cingulate cortex in autism.

The anterior cingulate cortex (ACC; BA 24) via its extensive limbic and high order association cortical connectivity to prefrontal cortex is a key part of an important circuitry participating in executive function, affect, and socio-emotional behavior. Multiple lines of evidence, including genetic and imaging studies, suggest that the ACC and gamma-amino-butyric acid (GABA) system may be affected in autism. The benzodiazepine binding site on the GABA(A) receptor complex is an important target for pharmacotherapy and has important clinical implications. The present multiple-concentration ligand-binding study utilized (3)H-muscimol and (3)H-flunitrazepam to determine the number (B(max)), binding affinity (K(d)), and distribution of GABA(A) receptors and benzodiazepine binding sites, respectively, in the ACC in adult autistic and control cases. Compared to controls, the autistic group had significant decreases in the mean density of GABA(A) receptors in the supragranular (46.8%) and infragranular (20.2%) layers of the ACC and in the density of benzodiazepine binding sites in the supragranular (28.9%) and infragranular (16.4%) lamina [corrected]. These findings suggest that in the autistic group this downregulation of both benzodiazepine sites and GABA(A) receptors in the ACC may be the result of increased GABA innervation and/or release disturbing the delicate excitation/inhibition balance of principal neurons as well as their output to key limbic cortical targets. Such disturbances likely underlie the core alterations in socio-emotional behaviors in autism.

Docking of 1,4-benzodiazepines in the alpha1/gamma2 GABA(A) receptor modulator site.

Positive allosteric modulation of the GABA(A) receptor (GABA(A)R) via the benzodiazepine recognition site is the mechanism whereby diverse chemical classes of therapeutic agents act to reduce anxiety, induce and maintain sleep, reduce seizures, and induce conscious sedation. The binding of such therapeutic agents to this allosteric modulatory site increases the affinity of GABA for the agonist recognition site. A major unanswered question, however, relates to how positive allosteric modulators dock in the 1,4-benzodiazepine (BZD) recognition site. In the present study, the X-ray structure of an acetylcholine binding protein from the snail Lymnea stagnalis and the results from site-directed affinity-labeling studies were used as the basis for modeling of the BZD binding pocket at the alpha(1)/gamma(2) subunit interface. A tethered BZD was introduced into the binding pocket, and molecular simulations were carried out to yield a set of candidate orientations of the BZD ligand in the binding pocket. Candidate orientations were refined based on known structure-activity and stereospecificity characteristics of BZDs and the impact of the alpha(1)H101R mutation. Results favor a model in which the BZD molecule is oriented such that the C5-phenyl substituent extends approximately parallel to the plane of the membrane rather than parallel to the ion channel. Application of this computational modeling strategy, which integrates site-directed affinity labeling with structure-activity knowledge to create a molecular model of the docking of active ligands in the binding pocket, may provide a basis for the design of more selective GABA(A)R modulators with enhanced therapeutic potential.

Nanomolar concentrations of pregnenolone sulfate enhance striatal dopamine overflow in vivo.

The balance between GABA-mediated inhibitory and glutamate-mediated excitatory synaptic transmission represents a fundamental mechanism for controlling nervous system function, and modulators that can alter this balance may participate in the pathophysiology of neuropsychiatric disorders. Pregnenolone sulfate (PS) is a neuroactive steroid that can modulate the activity of ionotropic glutamate and GABA(A) receptors either positively or negatively, depending upon the particular receptor subtype, and modulates synaptic transmission in a variety of experimental systems. To evaluate the modulatory effect of PS in vivo, we infused PS into rat striatum for 20 min via a microdialysis probe while monitoring local extracellular dopamine (DA) levels. The results demonstrate that PS at low nanomolar concentrations significantly increases extracellular DA levels. The PS-induced increase in extracellular DA is antagonized by the N-methyl-d-aspartate (NMDA) receptor antagonist, d-AP5 [d-(-)-2-amino-5-phosphonopentanoic acid], but not by the sigma receptor antagonist, BD 1063 [1(-)[2-(3,4-dichlorophenyl)-ethyl]-4-methylpiperazine]. The results demonstrate that exogenous PS, at nanomolar concentrations, is able to increase DA overflow in the striatum through an NMDA receptor-mediated pathway.

Novel statistical tools for monitoring the safety of marketed drugs.

Robust tools for monitoring the safety of marketed therapeutic products are of paramount importance to public health. In recent years, innovative statistical approaches have been developed to screen large post-marketing safety databases for adverse events (AEs) that occur with disproportionate frequency. These methods, known variously as quantitative signal detection, disproportionality analysis, or safety data mining, facilitate the identification of new safety issues or possible harmful effects of a product. In this article, we describe the statistical concepts behind these methods, as well as their practical application to monitoring the safety of pharmaceutical products using spontaneous AE reports. We also provide examples of how these tools can be used to identify novel drug interactions and demographic risk factors for adverse drug reactions. Challenges, controversies, and frontiers for future research are discussed.

A structured assessment of newly qualified medical graduates.

INTRODUCTION: While there is extensive published experience with the assessment of procedural skills in undergraduate students, this is limited in newly qualified medical graduates at the time of entry to the pre-registration (internship) year. The few studies that have been published suggest that these skills are frequently deficient when objectively tested. We therefore chose to assess the competence of a group of South African medical graduates on entry to their pre-registration year. METHODS: A total of 58 graduates of South African medical schools were assessed. Each subject participated in a 7-station objective structured clinical examination (OSCE); 6 of these assessed individual competence in phlebotomy, intramuscular injection, female pelvic examination, bladder catheterisation, tracheal intubation and prescription writing, while competence in cardiopulmonary resuscitation was assessed in a seventh station in randomly allocated teams of 3 candidates. Candidates' opinions of their own competence was sought by questionnaire. RESULTS: There was a wide variation in competence between subjects and across the range of tasks studied. Mean scores ranged from 85.4% for phlebotomy to 55.3% for prescription writing. The average score across all stations was 67.5%, and no student obtained an overall cut-off score of 85% or more, which was established using a modified Angoff method. Subjects' assessment of their own performance was unduly optimistic; most believed that they had demonstrated competence despite clear shortcomings in technique. Objective scores for subjects who had been exposed to a structured skills laboratory programme were not significantly higher than for those who had not, although their self-assessed performance was indeed higher. DISCUSSION: Most of the South African medical graduates who participated in this study were unable to satisfactorily perform technical procedures appropriate to the house officer on entry to the pre-registration year. This is in line with the conclusions of the few studies published in other countries. We suggest that the learning outcomes of undergraduate medical programmes should include an explicit statement of the competencies required for practice in the pre-registration year, and that these should be adequately taught and rigorously assessed before graduation.

Selective anxiolysis produced by ocinaplon, a GABA(A) receptor modulator.

Benzodiazepines remain widely used for the treatment of anxiety disorders despite prominent, often limiting side effects including sedation, muscle relaxation, and ataxia. A compound producing a robust anxiolytic action comparable to benzodiazepines, but lacking these limiting side effects at therapeutic doses (an anxioselective agent), would represent an important advance in the treatment of generalized anxiety disorder, and perhaps other anxiety disorders. Here we report that the pyrazolo[1,5-a]-pyrimidine, ocinaplon, exhibits an anxioselective profile in both preclinical procedures and in patients with generalized anxiety disorder, the most common of the anxiety disorders. In rats, ocinaplon produces significant muscle relaxation, ataxia, and sedation only at doses >25-fold higher than the minimum effective dose (3.1 mg/kg) in the Vogel "conflict" test. This anticonflict effect is blocked by flumazenil (Ro 15-1788), indicating that like benzodiazepines, ocinaplon produces an anxiolytic action through allosteric modulation of GABA(A) receptors. Nonetheless, in eight recombinant GABA(A) receptor isoforms expressed in Xenopus oocytes, the potency and efficacy of ocinaplon to potentiate GABA responses varied with subunit composition not only in an absolute sense, but also relative to the prototypical benzodiazepine, diazepam. In a double blind, placebo controlled clinical trial, a 2-week regimen of ocinaplon (total daily dose of 180-240 mg) produced statistically significant reductions in the Hamilton rating scale for anxiety scores. In this study, the incidence of benzodiazepine-like side effects (e.g., sedation, dizziness) in ocinaplon-treated patients did not differ from placebo. These findings indicate that ocinaplon represents a unique approach both for the treatment and understanding of anxiety disorders.

Inhibition of NMDA-induced striatal dopamine release and behavioral activation by the neuroactive steroid 3alpha-hydroxy-5beta-pregnan-20-one hemisuccinate.

Our laboratory has previously shown that the synthetic neuroactive steroid 3alpha-hydroxy-5beta-pregnan-20-one hemisuccinate (3alpha5betaHS) is a negative modulator of NMDA receptors in vitro. Similarly, 3alpha5betaHS exhibits rapid sedative, analgesic, anticonvulsive, and neuroprotective effects in vivo. Here we report a study designed to investigate whether a negatively charged neuroactive steroid, 3alpha5betaHS, modulates the action of NMDA receptors in vivo. Our results indicate that peripherally administered 3alpha5betaHS enters the CNS and inhibits NMDA-mediated motor activity and dopamine release in the rat striatum. The increase in motor activity induced by intrastriatal microinjection of NMDA was blocked by the systemic administration of 3alpha5betaHS and the NMDA-induced increase in extracellular dopamine in the striatum was also attenuated by both systemically administered and intrastriatally administered (by in vivo microdialysis) 3alpha5betaHS. These data indicate that 3alpha5betaHS acts through striatal NMDA receptors in vivo. When taken together, these results suggest that neuroactive steroids may prove to be effective in the treatment of neurological and psychiatric disorders involving over-stimulation of NMDA receptors in the mesotelencephalic dopamine system.

Distinct signal transduction pathways for GABA-induced GABA(A) receptor down-regulation and uncoupling in neuronal culture: a role for voltage-gated calcium channels.

Changes in GABA receptor (GABA(A)R) gene expression are detected in animal models of epilepsy, anxiety and in post-mortem schizophrenic brain, suggesting a role for GABA(A)R regulation in neurological disorders. Persistent (48 h) exposure of brain neurons in culture to GABA results in down-regulation of GABA(A)R number and uncoupling of GABA and benzodiazepine (BZD) binding sites. Given the central role of GABA(A)Rs in fast inhibitory synaptic transmission, GABA(A)R down-regulation and uncoupling are potentially important mechanisms of regulating neuronal excitability, yet the molecular mechanisms remain unknown. In this report we show that treatment of brain neurons in culture with tetrodotoxin, glutamate receptor antagonists, or depolarization with 25 mM K(+) fails to alter GABA(A)R number or coupling. Changes in neuronal activity or membrane potential are therefore not sufficient to induce either GABA(A)R down-regulation or uncoupling. Nifedipine, a voltage-gated Ca(2+) channel (VGCC) blocker, inhibits both GABA-induced increases in [Ca(2+)](i) and GABA(A)R down-regulation, suggesting that VGCC activation is required for GABA(A)R down-regulation. Depolarization with 25 mM K(+) produces a sustained increase in intracellular [Ca(2+)] without causing GABA(A)R down-regulation, suggesting that activation of VGCCs is not sufficient to produce GABA(A)R down-regulation. In contrast to GABA(A)R down-regulation, nifedipine and 25 mM K(+) fail to inhibit GABA-induced uncoupling, demonstrating that GABA-induced GABA(A)R down-regulation and uncoupling are mediated by independent molecular events. Therefore, GABA(A)R activation initiates at least two distinct signal transduction pathways, one of which involves elevation of intracellular [Ca(2+)] through VGCCs.

Developing an evidence base for interdisciplinary learning: a systematic review.

AIM OF THE STUDY: The overall aim of the study was to explore the feasibility of introducing interdisciplinary education within undergraduate health professional programmes. This paper reports on the first stage of the study in which a systematic review was conducted to summarize the evidence for interdisciplinary education of undergraduate health professional students. METHODS: Systematic reviews integrate valid information providing a basis for rational decision making about health care which should be based on empirical and not anecdotal evidence. The accepted principles for systematic reviews were adapted in order to allow integration of the literature to produce recommendations for educational practice and guidelines for future research. FINDINGS: The literature on interdisciplinary education was found to be diverse, including relatively small amounts of research data and much larger amounts of evaluation literature. Methodological rating schemes were used to test for confounding influences in the research studies. The number of studies found was 141 but only 30 (21%) were included in the analysis because of lack of methodological rigour in the research and poorly developed outcome measures. CONCLUSIONS: Student health professionals were found to benefit from interdisciplinary education with outcome effects primarily relating to changes in knowledge, skills, attitudes and beliefs. Effects upon professional practice were not discernible and educational and psychological theories were rarely used to guide the development of the educational interventions.

Training, job demands and mental health of pre-registration house officers.

OBJECTIVES: This study aims to explore pre-registration house officer (PRHO) perceptions of work role, job requirements and mental health, in order to enhance work role preparation by means of identifying potential areas for curriculum development. DESIGN: Phase 1 took place 6 weeks before completion of the pre-registration year. A total of 56 PRHOs completed questionnaires which included a diary of activities, recorded daily over a 2-week period (ward rounds, on-call, audit, administration, continuing medical education, etc.), items relating to perceived occupational control, and the Maslach Burnout Inventory. In phase 2, in the final 2 weeks of the preregistration year, 36% (n=18) of phase 1 participants were randomly selected for interview. SETTING: Three hospitals in the North-west of England. RESULTS: The average working week was 56 h, with 10% working in excess of this figure. The average weekly proportion of time spent on organized continuing medical education was 5%. Routine administrative tasks took up one-fifth of PRHO time and were perceived as lacking in training or educational elements. Of the PRHOs, 52% (n=29) desired further advice/training on the technical and management aspects of the job. Additional training was required on topics such as chest drains, delegation and time management. PRHOs felt this should be given prior to commencement of the pre-registration year. In terms of mental health, 25% (n=14) were experiencing burnout. Occupational control was external; many individuals perceived events as often occurring outside individual control. CONCLUSIONS: These findings have implications for the undergraduate curriculum and support General Medical Council recommendations for curriculum reform. It is suggested that organizational skills such as managing responsibility/delegation and additional training in practical procedures should be an integral part of the medical undergraduate curriculum.

Learning gross anatomy in a clinical skills course.

Recent developments in undergraduate medical education in the United Kingdom have produced changes in the content and delivery of component courses, including human anatomy. Anatomy can retain its place in the medical course in the new world of problem-based learning and clinical skills teaching by gaining recognition as an integral part of the curriculum which underpins much of the practice of clinical medicine. In these new courses, anatomical information is clinically relevant and discussed in the context of medical problems and the acquisition of clinical skills. Students are encouraged to study in a manner in which information is retained (deep learning) and where understanding replaces rote learning of facts. Students take responsibility for their own learning, with appropriate support and resources. In clinical skills courses, anatomy underpins the development and retention of clinical knowledge and skills.

The burden of infection with HSV-1 and HSV-2 in England and Wales: implications for the changing epidemiology of genital herpes.

OBJECTIVE: To measure the burden of infection with herpes simplex type 1 (HSV-1) and herpes simplex type 2 (HSV-2) in the general population of England and Wales and to assess temporal changes in the incidence of HSV-1 infection in childhood. METHODS: 4930 residual blood samples taken from people aged 0-69 years and submitted to 15 public health laboratories in England and Wales between January 1994 and June 1995, and 500 samples taken from people aged 10-14 years between November 1986 and December 1987, were screened for IgG antibody to HSV-1 and HSV-2 using type specific ELISA assays. RESULTS: The prevalence of antibody to HSV-1 in 10-14 year olds declined from 34% in samples collected in 1986-7 to 24% in samples collected in 1994-5 (p < 0.001). HSV-1 antibody prevalence in adults increased with age and was higher in females than males, reaching 54% in females aged 25-30 years in 1994-5. In samples collected in 1994-5 from people aged 16-69 years HSV-2 antibody was detected in sera from 3.3% of men and 5.1% of women. CONCLUSIONS: The incidence of HSV-1 infection in childhood is falling in England and Wales. The prevalence of HSV-2 infection in the general population is low, with the rate of infection significantly lower than that described for the general population in the United States and developing countries. The falling rate of HSV-1 infection in childhood may be one factor contributing to the increasing incidence of genital HSV-1 infection.

A monoclonal blocking EIA for herpes simplex virus type 2 antibody: validation for seroepidemiological studies in Africa.

A competitive type-specific enzyme-linked immunosorbent assay (ELISA) for herpes simplex virus type 2 (HSV-2) antibody was developed using an infected cell antigen and a monoclonal antibody to glycoprotein G-2. This assay has been validated for use for epidemiological studies using a large panel of sera collected in rural Uganda and a panel of 143 sera characterised previously by Western blotting, the 'gold standard' for HSV type-specific serology. This evaluation was found to have a sensitivity of 96% and a specificity of 91% in comparison with Western blot on 143 sera from clinic patients. The ELISA had a sensitivity of 93% and a specificity of 91% in comparison with Western blot on 495 sera collected in Uganda. The assay showed good reproducibility and a low percentage of sera gave equivocal results, indicating its suitability for epidemiological studies.

Geometry and charge determine pharmacological effects of steroids on N-methyl-D-aspartate receptor-induced Ca(2+) accumulation and cell death.

Modulation of N-methyl-D-aspartate (NMDA) receptor function by a series of sulfated steroids and dicarboxylic acid ester analogs of pregnenolone sulfate and pregnanolone sulfate was investigated in cultured hippocampal neurons. The "bent" steroid ring structure associated with 5beta-stereochemistry favors receptor inhibition, whereas the more planar ring structure of the pregn-5-enes and 5alpha-pregnanes favors potentiation of NMDA-induced [Ca(2+)] increases and neuronal cell death. The nature of the negatively charged group attached to the steroid C3 position is important for both the neuroprotection afforded by pregnane steroids and the exacerbation of NMDA-induced neuronal death by pregn-5-enes. Dicarboxylic acid hemiesters of various lengths can substitute for the sulfate group of the positive modulator pregnenolone sulfate and the negative modulator pregnanolone sulfate. This result suggests that precise coordination with the oxygen atoms of the sulfate group is not critical for modulation and that the steroid recognition sites can accommodate bulky substituents at C3. The capacity of charged steroids to enhance or protect against NMDA-induced death of hippocampal neurons is strongly correlated with modulation of NMDA-induced Ca(2+) accumulation, indicating that direct enhancement or inhibition of NMDA receptor function is responsible for the proexcitotoxic or neuroprotective effects of these steroids.

Turnover and down-regulation of GABA(A) receptor alpha1, beta2S, and gamma1 subunit mRNAs by neurons in culture.

Benzodiazepines (BZDs), barbiturates, ethanol, and general anesthetics potentiate the action of gamma-aminobutyric acid (GABA) at the type A GABA receptor (GABA(A)R) and have profound effects on mood, arousal, and susceptibility to seizures. GABA(A)R number and subunit mRNA levels change in animal models of epilepsy and anxiety and following exposure to GABA(A)R agonists and positive modulators, but the mechanism of receptor down-regulation remains unknown. Persistent exposure (48 h) of brain neurons in primary culture to GABA results in a 30% decrease in the levels of mRNA encoding the alpha1, beta2S, and gamma1 GABA(A)R subunit isoforms, which form a receptor enhanced by nonselective BZDs. Down-regulation of alpha1 mRNA (t1/2 = 8 h) precedes down-regulation of receptor number (t1/2 = 25 h), suggesting that GABA-induced GABA(A)R down-regulation is a consequence of decreased mRNA levels. The apparent half-life of the alpha1 mRNA in the presence of alpha-amanitin (9 h) is consistent with the time course of alpha1 mRNA down-regulation. Moreover, the stability of the alpha1, beta2S, and gamma1 subunit mRNAs is not altered by chronic GABA exposure. The results demonstrate that GABA(A)R subunit mRNA down-regulation is not a consequence of accelerated mRNA degradation and argue that GABA-induced GABA(A)R down-regulation is due to inhibition of transcription.

Illicit drug use related attendances at accident and emergency services in Aberdeen: a prospective six month survey.

OBJECTIVE: To quantify and examine the nature of known illicit drug related attendances at the Accident and Emergency Department of Aberdeen Royal Hospital over a six month period. DESIGN: A structured questionnaire was completed by Accident and Emergency staff. SETTING: The Accident and Emergency Department of Aberdeen Royal Hospital. SUBJECTS: All patients presenting at the Accident and Emergency Department as a result of known illicit drug use between November 1996 to April 1997 inclusive. RESULTS: One hundred and fifty seven subjects presented at Accident and Emergency during the six month period. Peak attendance was between 18.00 and 21.00 hours. Twenty seven percent of patients chose to visit Accident and Emergency rather than their own general practitioner. Thirty seven percent had no involvement with any health care professional regarding their drug use. Heroin was used by 62% of cases of which the majority (94.9%) had injected and stimulants such as amphetamine and ecstasy were used by a large proportion of cases. Only 4.5% of subjects admitted to not using clean equipment yet 15% admitted to have loaned equipment (to someone else) and 22% of subjects had injecting related problems. Thirteen percent of subjects were considered unco-operative by staff. Fifty four percent of subjects required admission to a ward and ten patients (6%) died. CONCLUSION: Heroin continues to be the main drug causing major health problems. Harm reduction messages are not adequately reaching/or being taken up by drug users given the high proportion with injecting related problems and those being prepared to lend needles. The receptive attitude amongst subjects highlighted the opportunity for patient education as well as giving contact addresses of relevant organisations.

Dueling enigmas: neurosteroids and sigma receptors in the limelight.

Neurosteroids can be positive or negative regulators of neurotransmitter receptor action, depending on the receptor and the chemical structure of the neurosteroid. This Perspective by Gibbs and Farb is one of two on the subject of neurosteroids. The authors address the possible role of sigma receptors in mediating neurosteroid action and describe how the regulation of inhibitory and excitatory ion channels by neurosteroids has implications for the role of these molecules in learning and memory, nociception, and excitotoxicity.