Student test scores are improved in a virtual learning environment.

This study evaluates the effectiveness of delivering the core curriculum of an introductory neuroscience course using a software application referred to as a virtual learning interface (VLI). The performance of students in a virtual learning environment (VLE) is compared with that of students in a conventional lecture hall in which the same lecturer presented the same material. This study was not designed to determine whether grades are improved by augmenting a lecture with other information. The VLI takes advantage of audio, video, animation, and text in a multimedia computer environment. Our results indicate that raw average scores on weekly examinations were 14 percentage points higher for students in the VLE compared with those for students in a conventional lecture hall setting. Moreover, normalized test scores were over 5 points higher for students in the VLE. This analysis suggest that a core curriculum can be effectively presented to students using the VLE, thereby making it possible for faculty to spend less class time relaying facts and more time engaging students in discussion of scientific theory.

Relation between aerobic fitness level and stress induced alterations in neuroendocrine and immune function.

Alterations in neuroendocrine and immune function were examined in sedentary (n=15) (VO2peak; 31.4+/-0.7 ml x kg(-1) x min(-1); 24.4+/-1.2yr), moderately active (n=15) (VO2peak; 45.4+/-1.1 ml x kg(-1) x min(-1); 24.2+/-1.1 yr) and aerobically trained (n=15) (VO2peak; 58.8+/-0.9 ml x kg(-1) x min(-1); 24.3+/-1.0 yr) men following exposure to an acute mild psychological stressor. Subjects had 2 min to prepare, and 3 min to deliver a speech in front of 3 observers. Blood samples were drawn from an indwelling catheter before, during and 30 min following the speech task (ST). Self-reported measures of anxiety were obtained prior to and immediately following the stressor. The ST resulted in significant alterations in the number and function of immune cells, and in self-reported anxiety scores. Plasma levels of norepinephrine increased during the speech task. The neuroendocrine and immune response to the chosen stressor were independent of subject aerobic fitness level.

Protein secondary structure modelling with probabilistic networks.

In this paper we study the performance of probabilistic networks in the context of protein sequence analysis in molecular biology. Specifically, we report the results of our initial experiments applying this framework to the problem of protein secondary structure prediction. One of the main advantages of the probabilistic approach we describe here is our ability to perform detailed experiments where we can experiment with different models. We can easily perform local substitutions (mutations) and measure (probabilistically) their effect on the global structure. Window-based methods do not support such experimentation as readily. Our method is efficient both during training and during prediction, which is important in order to be able to perform many experiments with different networks. We believe that probabilistic methods are comparable to other methods in prediction quality. In addition, the predictions generated by our methods have precise quantitative semantics which is not shared by other classification methods. Specifically, all the causal and statistical independence assumptions are made explicit in our networks thereby allowing biologists to study and experiment with different causal models in a convenient manner.

Radiofrequency catheter ablation for treatment of bundle branch reentrant ventricular tachycardia: results and long-term follow-up.

Seven of 120 consecutive patients with inducible sustained ventricular tachycardia (from September 1, 1988 to January 1, 1991) had bundle branch reentrant tachycardia and underwent percutaneous radiofrequency ablation of the right bundle branch. The seven patients had been unsuccessfully treated with a mean of 3 +/- 1 drugs. Four patients presented with syncope and three with aborted sudden death. The baseline electrocardiogram revealed a left bundle branch block pattern in three patients and an intraventricular conduction defect in four. The baseline HV interval was prolonged in each case (79 +/- 2 ms). With use of programmed ventricular extrastimuli, sustained bundle branch reentrant tachycardia was inducible in all patients at a mean cycle length of 283 +/- 17 ms (range 230 to 350). Bundle branch reentrant tachycardia characteristics included atrioventricular dissociation, a His deflection that preceded each QRS complex and spontaneous His to His variation that preceded changes in ventricular tachycardia cycle length. A quadripolar catheter was positioned across the tricuspid valve with the distal electrode tip of the catheter near the right bundle branch. One to three applications of continuous unmodulated radiofrequency current at 300 kHz between the distal electrode and a large posterior skin patch resulted in complete right bundle branch block in all patients, after which none had inducible bundle branch reentrant tachycardia on restudy. On restudy, three of the seven patients had ventricular tachycardia of myocardial origin (not bundle branch reentry). One patient required no therapy; drug or defibrillator therapy was used in the others.(ABSTRACT TRUNCATED AT 250 WORDS)

The DNA binding arm of lambda repressor: critical contacts from a flexible region.

Segments of protein that do not adopt a well-ordered conformation in the absence of DNA can still contribute to site-specific recognition of DNA. The first six residues (NH2-Ser1-Thr2-Lys3-Lys4-Lys5-Pro6-) of phage lambda repressor are flexible but are important for site-specific binding. Low-temperature x-ray crystallography and codondirected saturation mutagenesis were used to study the role of this segment. All of the functional sequences have the form [X]1-[X]2-[Lys or Arg]3-[Lys]4-[Lys or Arg]5-[X]6. A high-resolution (1.8 angstrom) crystal structure shows that Lys3 and Lys4 each make multiple hydrogen bonds with guanines and that Lys5 interacts with the phosphate backbone. The symmetry of the complex breaks down near the center of the site, and these results suggest a revision in the traditional alignment of the six lambda operator sites.

Percutaneous catheter modification of the atrioventricular node. A potential cure for atrioventricular nodal reentrant tachycardia.

Our purpose was to describe a technique of atrioventricular (AV) node modification for patients with drug refractory AV nodal reentrant tachycardia (AVNRT). Nine patients (mean age, 45 +/- 20; range, 14-82) with recurrent drug refractory AVNRT (n = 8) or sudden cardiac death thought to be precipitated by AVNRT (n = 1) underwent a percutaneous catheter procedure to modify AV nodal function. The area between the electrode recording the maximal His-bundle electrogram and the ostium of the coronary sinus was divided into three zones. Perinodal direct current shocks of 100-300 J were delivered to one (n = 2), two (n = 3), or three (n = 4) zones without complications. The procedure endpoints were modification of AV conduction (either first degree AV block or complete retrograde ventriculo-atrial [VA] block) and failure to induce AVNRT before or after isoproterenol and/or atropine administration. Six of nine patients (67%) have had no inducible or spontaneous AVNRT over a mean follow-up of 12.3 +/- 4.1 months (range, 4.5-17). One of the six underwent repeat, successful modification, because AVNRT was inducible at restudy 2 days after the initial procedure. AVNRT recurred in three patients (33%), one early (3 days) and two late (3-4 months). Two of these patients underwent complete ablation of the AV junction and permanent pacemaker placement, whereas one is controlled with drug therapy. Therefore, AV nodal modification resulted in tachycardia control without antiarrhythmic drugs in six of nine (67%) and obviated the need for complete AV junctional ablation in seven of nine patients (78%). Elimination of AVNRT appears to result from either block in the retrograde fast pathway or modification of the antegrade slow pathway, such that AVNRT cannot be sustained. Additional findings suggest that an atrio-Hisian accessory connection may not be involved in AVNRT in some of these patients. Percutaneous catheter AV nodal modification appears to be a promising technique for treatment of refractory AVNRT and may obviate need for complete AV junctional ablation in a substantial number of patients with drug/pacemaker refractory AVNRT.