What is happening to the monocotyledons?

An attempt is made to elucidate some of the more pronounced departures from traditional classifications in the book The families of the monocotyledons byDahlgren and collaborators, which embodies the latest opinions of the lateRolf Dahlgren on the subject. Consideration is given to the treatment of theLiliiflorae (especiallyLiliales andAsparagales) andBromeliiflorae, and to the theory offered for the origin of the monocots which identifies theDioscoreales as the most primitive order of the subclass.Dahlgren aimed at an eclectic classification (one based on a combination of similarity criteria and phylogenetic criteria) and the results of his use of cladistic methods (in association withF. N. Rasumssen) to supply the phylogenetic input are assessed. The resulting system itself is considered in the light of the distinction drawn byJ. S. L. Gilmour between natural and artificial classifications and their respective uses.Dedicated to the memory of JohnS. L. Gilmour.     

Inappropriate defibrillator shock due to oversensing. What is the mechanism?

Implantable cardioverter defibrillator (ICD) is often advised for secondary prevention of sudden cardiac death. Inappropriate shocks from ICD is uncommon but can seriously affect the quality of life. One of the reasons for inappropriate ICD shock is loose set screw, which may remain undetected by device interrogation and/or fluoroscopy. A 55-year lady presented with multiple inappropriate shocks few hours after an ICD implantation. The discrepancy between near field (NF, tip to ring) and far field (FF, Can to RV coil) signals helped us to suspect noise related to loose set screw, as the underlying problem. Re-exploration of the pocket had to be performed as the last resort to confirm the diagnosis and rectify the problem.     

Sudden unexpected improvement in the atrioventricular conduction. What is the mechanism?

The 12-lead electrocardiogram (ECG) of a 79-year-old male patient with recurrent pre-syncope showed irregular sinus rhythm with constant PR interval and left bundle branch block (LBBB) with intermittently blocked P waves. The beat following the blocked P wave had a narrower QRS with a shorter PR interval. The phenomenon of bilateral bundle branch block explains the sudden improvement in the atrioventricular conduction.     

What is the best approach to treating schizophrenia in developing countries?

BACKGROUND TO THE DEBATE: Schizophrenia affects an estimated 25 million people in low- and middle-income countries, with an average lifetime risk of about 1%. The illness is associated with excess mortality from a variety of causes. A 2001 Institute of Medicine report on mental illness in developing countries found that in 1990, over two-thirds of people with schizophrenia in these countries were not receiving any treatment (http://www.nap.edu/catalog/10111.html). The report found no evidence that the proportion of treated people in the developing world had increased since 1990. There is now a debate among mental health professionals in low-income countries over how best to improve patient care. In this article, three psychiatrists give their different viewpoints on the current status of treatment efforts for schizophrenia in the developing world and the measures that can be taken to increase the proportion of patients receiving treatment.     

What Is the Optimal Threshold at Which to Recommend Breast Biopsy?

Background

A 2% threshold, traditionally used as a level above which breast biopsy recommended, has been generalized to all patients from several specific situations analyzed in the literature. We use a sequential decision analytic model considering clinical and mammography features to determine the optimal general threshold for image guided breast biopsy and the sensitivity of this threshold to variation of these features.

Methodology/Principal Findings

We built a decision analytical model called a Markov Decision Process (MDP) model, which determines the optimal threshold of breast cancer risk to perform breast biopsy in order to maximize a patient’s total quality-adjusted life years (QALYs). The optimal biopsy threshold is determined based on a patient’s probability of breast cancer estimated by a logistic regression model (LRM) which uses demographic risk factors (age, family history, and hormone use) and mammographic findings (described using the established lexicon–BI-RADS). We estimate the MDP model''s parameters using SEER data (prevalence of invasive vs. in situ disease, stage at diagnosis, and survival), US life tables (all cause mortality), and the medical literature (biopsy disutility and treatment efficacy) to determine the optimal “base case” risk threshold for breast biopsy and perform sensitivity analysis. The base case MDP model reveals that 2% is the optimal threshold for breast biopsy for patients between 42 and 75 however the thresholds below age 42 is lower (1%) and above age 75 is higher (range of 3–5%). Our sensitivity analysis reveals that the optimal biopsy threshold varies most notably with changes in age and disutility of biopsy.

Conclusions/Significance

Our MDP model validates the 2% threshold currently used for biopsy but shows this optimal threshold varies substantially with patient age and biopsy disutility.     

What is signal and what is noise in the brain?

The response of a cortical neuron to a stimulus can show a very large variability when repeatedly stimulated by exactly the same stimulus. This has been quantified in terms of inter-spike-interval (ISI) statistics by several researchers (e.g., [Softky, W., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13(1), 334-350.]). The common view is that this variability reflects noisy information processing based on redundant representation in large neuron populations. This view has been challenged by the idea that the apparent noise inherent in brain activity that is not strictly related or temporally coupled to the experiment could be functionally significant. In this work we examine the ISI statistics and discuss these views in a recently published model of interacting cortical areas [Knoblauch, A., Palm, G., 2002. Scene segmentation by spike synchronization in reciprocally connected visual areas. I. Local effects of cortical feedback. Biol. Cybernet. 87(3), 151-167.]. From the results of further single neuron simulations we can isolate temporally modulated synaptic input as a main contributor for high ISI variability in our model and possibly in real neurons. In contrast to alternative mechanisms, our model suggests a function of the temporal modulations for short-term binding and segmentation of figures from background. Moreover, we show that temporally modulated inputs lead to ISI statistics which fit better to the neurophysiological data than alternative mechanisms.     

What is the ultimate goal in acid-base regulation?

It is common to see chapters on acid-base physiology state that the goal of acid-base regulatory mechanisms is to maintain the pH of arterial plasma and not arterial Pco(2) (Pa(CO(2))) or plasma HCO(3). A hypothetical situation in which the Pa(CO(2)) of arterial plasma is 80 mmHg and the plasma HCO(3) concentration is 48 mM is presented and analyzed to get over this misconception. As per the modified Henderson equation, the pH of arterial plasma would be 7.4; however, we explain that this may be associated with intracellular acidosis due to intracellular hypercapnia and that derangement of homeostasis is evident from the occurrence of respiratory depression and, eventually, coma in the patient described. This suggests that the ultimate goal of acid-base regulatory mechanisms is not just the maintenance of the pH of arterial plasma but the maintenance of the steady-state pH of intracellular fluid as well.     

What is new in the treatment of hypospadias?

Hypospadias is a congenital anomaly characterized by a ventrally placed urethral meatus in a more proximal position on the midline than its normal position in the glanular part of the penis. In 1961, C. E. Horton and C. J. Devine, Jr., developed single-stage modern surgical techniques, namely, local skin flaps and free skin grafts, for urethra reconstruction in hypospadias repair, which may be applied to almost any case with different localizations of the meatus. Later, two new methods, advancement of the urethra and preputial island flap techniques, were added to the surgical algorithm. Because acceptable results were observed, the authors have insisted on using these four techniques for all hypospadias cases since 1972. Complication rates (mainly fistula formation) were quite high (50 percent) in their early series of adults as a result of erection and hematoma formation. The complication rate of their patient population, which is now mainly composed of preschool children, has decreased to 7 to 8 percent, primarily as a result of careful selection of appropriate techniques for each individual case, the development of better surgical materials and equipment, and taking necessary precautions for postoperative care. A brief summary of modern hypospadias repair techniques is presented in four major classes. The results of the authors' 30-year experience and the precautions necessary to avoid postoperative complications are evaluated. The authors conclude that the four modern techniques and their modifications should be performed meticulously for successful hypospadias repair.     

Adenosine-sensitive perinodal atrial tachycardia. What is the mechanism?

Termination of focal atrial tachycardia with adenosine is considered a defining feature for triggered activity. Recent evidence, however, suggests that the perinodal adenosine-sensitive AT has reentry as the mechanism of tachycardia. In this report, we were able to confirm the mechanism of AT as reentry by observing the response to programmed electrical stimulation and demonstrating the fallacy of traditional teaching that the adenosine responsiveness of AT is a criterion for labeling the mechanism as triggered activity.