Reentry as an Origin for Rotors.

The aim of the study is to understand in depth the meaning of "reentry", and to decipher if and how it can lead to malfunctions of the heart and possibly of the brain. A simple model is used to reveal the mechanism by which a single pulse of action potential rotating around a ring of excitable medium, the latter simulating a reentry circuit, can generate spirals (single and/or double) when the pulse can emerge from and develop outside the ring. Two mechanisms of spiral generation are demonstrated: (1) a mechanism in which a source of single spirals is created at the contact with the core soon after the pulse freeing action, their chirality being due to the sense of the preceding pulse rotation. Interestingly, these spirals, adhering to the core, become "double-spiral patterns" while leaving behind the seeds of the new single spirals. (2) A second possible mechanism, similar to the known "arms encountering methods", in which a double spiral (a figure of eight) is repeatedly created on the other side of the core. Similar procedures are assumed to occur in the heart, leading to tachycardia and fibrillation and possibly in the brain leading to epilepsy. The exact processes of the hitherto assumed spiral generations by reentry were established. The novel deep understanding of the mechanisms involved in these processes can lead to new methods of treating heart fibrillation (e.g., by judicial ablation).

Ergot Use and Overuse: A Pharmacoepidemiology Retrospective Cohort Study.

OBJECTIVE: The objective of this study was to estimate and to characterize the actual patterns of ergot use and overuse in France using a drug reimbursement database. METHODS: We included all people covered by the French General Health Insurance System (GHIS) from the Provence-Alpes-Côte-d'Azur (PACA) and Corsica administrative areas who had at least one prescription of ergot between May 2010 and December 2011. All prescriptions of ergots, migraine prophylactic treatment, and psychotropic medications were extracted from the GHIS database. We defined occasional ergot users (<3 months of prescription) and regular ergot users (>3 months of prescription). Among regular ergot users, we identified overusers and nonoverusers. RESULTS: We included 4358 patients who had at least one prescription of ergots (oral ergotamine tartrate, dihydroergotamine mesilate nasal spray, intravenous dihydroergotamine mesilate). Among ergot overusers, a large majority of patients had ergotamine tartrate overuse. The proportion of ergotamine tartrate overusers is maximum after 55 years. Compared with regular users, overusers use more frequently a prophylactic treatment (93/165 [56.4%] versus 398/1057, OR = 2.15, P < .001), antidepressants (72/165 [43.6%] versus 326/1057 [30.8%] OR = 1.79, P < .001), benzodiazepines (111/165 [67.3%] versus 613/1057 [58.0%], OR = 1.50, P < .001), weak opioids (95/165 [57.6%] versus 463/1057 [43.8], OR = 1.77, P < .001) and strong opioids (13/165 [7.9%] versus 24/1057 [2.3%], OR = 3.86, P < .001). The coexistence of ergot consumption and triptan overuse, and the possibility of both triptan and ergot overuse was described; triptan overusers were more described in ergotamine overusers than in nonoverusers. CONCLUSIONS: This work outlines a high prevalence of ergotamine tartrate overuse (11.1%). As ergotamine tartrate users are mostly aged more than 55 years, an evaluation of ergotamine cardiovascular risk profile is necessary in the elderly population.

[What can we expect from clinical trials in psychiatry?] / Que peut-on attendre des essais cliniques en psychiatrie ?

Clinical trials in psychiatry allow to build the regulatory dossiers for market authorization but also to document the mechanism of action of new drugs, to build pharmacodynamics models, evaluate the treatment effects, propose prognosis, efficacy or tolerability biomarkers and altogether to assess the impact of drugs for patient, caregiver and society. However, clinical trials have shown some limitations. Number of recent dossiers failed to convince the regulators. The clinical and biological heterogeneity of psychiatric disorders, the pharmacokinetic and pharmacodynamics properties of the compounds, the lack of translatable biomarkers possibly explain these difficulties. Several breakthrough options are now available: quantitative system pharmacology analysis of drug effects variability, pharmacometry and pharmacoepidemiology, Big Data analysis, brain modelling. In addition to more classical approaches, these opportunities lead to a paradigm change for clinical trials in psychiatry.

Detection of signals of abuse and dependence applying disproportionality analysis.

INTRODUCTION: Prescription drug abuse and dependence is a widespread phenomenon in many countries. The use of disproportionality measures in drug abuse surveillance is rarely performed. PURPOSE: The aim of this study is to determine the occurrence of signals of abuse and dependence for different psychoactive drugs in real-life settings. METHODS: Disproportionality analysis was realised from a database specifically constructed for the monitoring of drug abuse and dependence. This database provides information on approximately 5000 patients and 8000 consumption modalities for more than 100 distinct psychoactive medications for 2010 and 2011. Proportional reporting ratio (PRR) was computed in two population groups: subjects under an opiate maintenance treatment (OMT) versus those not under OMT, and focused on four types of behaviours: abuse and dependence, illegal acquisition, diverted route of administration and concomitant alcohol use. RESULTS: Among the 100 psychoactive drugs for which a signal could be detected, those presenting the highest signals were the following: flunitrazepam, clonazepam, methylphenidate, ketamine, morphine sulfate, codeine and buprenorphine. CONCLUSIONS: The present study shows an innovative application of disproportionality measures for drug abuse monitoring based on two cross-national, annual studies. The disproportionality analysis provided the opportunity to reveal and compare the magnitude of signals between 100 psychoactive drugs. This approach helps to compare the magnitude of abuse and dependence behaviours for a large number of drugs, and allows prioritizing actions in a context where such events are usually underreported.

The Baroreflex Mechanism Revisited.

We state that the autonomic part of the brain controls the blood pressure (BP) and the heart rate (HR) via the baroreflex mechanism in all situations of human activity (at sleep, at rest, during exercise, fright etc.), in a way which is not, as was hitherto assumed, a mere homeostatic tool or even a resetting device, designed to bring these variables on the road to preset values. The baroreflex is rather a continuous feedback mechanism commanded by the autonomic part of the brain, leading to values appropriate to the situation at hand. Feasibility of this assertion is demonstrated here by using the Seidel-Herzel feedback system outside of its regular practice. Results show indeed that the brain can, and we claim that it does, control the HR and BP throughout life. New responses are demonstrated, e.g., to a sudden fear or apnea. In this event, large BP and HR overshoots are expected before the variables can relax to a new level. Response to abrupt downward change in the controlling parameter shows an undershoot in HR and just a gradual resetting in the BP. The relaxation from sudden external changes to various expected states are calculated and discussed and properties of the Rheos test are explained. Experimental findings for orthostatic tests and for babies under translations and rotations reveal complete qualitative agreement with our model and show no need to invoke the operation of additional body systems. Our method should be the preferred one by the Occam Razor approach. The outcomes may lead to beneficial clinical implication.

Singular Value Decomposition of Optically-Mapped Cardiac Rotors and Fibrillatory Activity.

Our progress of understanding how cellular and structural factors contribute to the arrhythmia is hampered in part because of controversies whether a fibrillating heart is driven by a single, several, or multiple number of sources, and whether they are focal or reentrant, and how to localize them. Here we demonstrate how a novel usage of the neutral singular value decomposition (SVD) method enables the extraction of the governing spatial and temporal modes of excitation from a rotor and fibrillatory waves. Those modes highlight patterns and regions of organization in the midst of the otherwise seemingly-randomly propagating excitation waves. We apply the method to experimental models of cardiac fibrillation in rabbit hearts. We show that the SVD analysis is able to enhance the classification of the heart electrical patterns into regions harboring drivers in the form of fast reentrant activity and other regions of by-standing activity. This enhancement is accomplished without any prior assumptions regarding the spatial, temporal or spectral properties of those drivers. The analysis corroborates that the dominant mode has the highest activation rate and further reveals a new feature: A transfer of modes from the driving to the passive regions resulting in a partial reaction of the passive region to the driving region.

Possible mechanism of schizophrenia origin by excess GABA and synaptic pruning.

Schizophrenia is a psychotic disorder that affects approximately 1% of the global population. However, the etiology of this illness remains a subject of debate. One of the proposed mechanisms underlying schizophrenia is the synaptic pruning mediated by microglia in the brains of individuals with schizophrenia, although the precise mechanisms of this process remain elusive. In this regard, we propose that the potential development of the disease stems from both a genetic predisposition leading to an excessive production of GABAergic neurons and an exaggerated effort to maintain the E/I (excitation/inhibition) balance in the brain.

A possible new cardiac heterogeneity as an arrhythmogenic driver.

Atrial fibrillation (AF) is the commonest cardiac arrhythmia, affecting 3 million people in the USA and 8 million in the EU (according to the European Society of Cardiology). So, why is it that even with the best medical care, around a third of the patients are treatment resistant. Extensive research of its etiology showed that AF and its mechanisms are still debatable. Some of the AF origins are ascribed to functional and ionic heterogeneities of the heart tissue and possibly to additional triggering agents. But, have all AF origins been detected? Are all accepted origins, in fact, arrhythmogenic? In order to study these questions and specifically to check our new idea of intermittency as an arrhythmogenesis agent, we chose to employ a mathematical model which was as simple as possible, but which could still be used to observe the basic network processes of AF development. At this point we were not interested in the detailed ionic propagations nor in the actual shapes of the induced action potentials (APs) during the AF outbreaks. The model was checked by its ability to exactly recapture the basic AF developmental stages known from experimental cardiac observations and from more elaborate mathematical models. We use a simple cellular automata 2D mathematical model of N × N matrices to elucidate the field processes leading to AF in a tissue riddled with randomly distributed heterogeneities of different types, under sinus node operation, simulated by an initial line of briefly stimulated cells inducing a propagating wave, and with or without an additional active ectopic action potential pulse, in turn simulated by a transitory operation of a specific cell. Arrhythmogenic contributions, of three different types of local heterogeneities in myocytes and their collaborations, in inducing AF are examined. These are: a heterogeneity created by diffuse fibrosis, a heterogeneity created by myocytes having different refractory periods, and a new heterogeneity type, created by intermittent operation of some myocytes. The developmental stages (target waves and spirals) and the different probabilities of AF occurring under each condition, are shown. This model was established as being capable of reproducing the known AF origins and their basic development stages, and in addition has shown: (1) That diffuse fibrosis on its own is not arrhythmogenic but in combination with other arrhythmogenic agents it can either enhance or limit AF. (2) In general, combinations of heterogeneities can act synergistically, and, most importantly, (3) The new type of intermittency heterogeneity proves to be extremely arrhythmogenic. Both the intermittency risk and the fibrosis role in AF generation were established. Knowledge of the character of these arrhythmogenesis agents can be of real importance in AF treatment.

Origin of post-ictal and post-anesthesia adverse effects and possibly of SUDEP.

The origin of post-ictal malfunctions is debatable. We want to propose a novel idea of a cause of these adverse results occurring following epileptic seizures and anesthesia. Previously we have put forward the idea that epileptic seizures termination is caused by the function of the glymphatic system in the brain. A new measurement shows that this system can be much faster than what was estimated before. Moreover, the method enabling this speeding was actually measured in brains of epilepsy subjects. So, the main objection to our model is relegated. As a possible consequence of the glymphatic process, there can be an excess cleaning of the brain's interstitial fluid. We discuss possible adverse results of this process. This over-cleaning (that can, to a lower extent, occur also during anesthesia) which results post-ictally from the previous overexpression of fluid materials by the neurons during their seizure operation, can reduce ingredients essential for regular neuronal functioning, thereby leading to function reduction and EEG suppression which last until those materials are replenished. We argue that this ingredients' scarcity is the cause of post-ictal generalized EEG suppression (PGES), of post-ictal immobility (PI) and possibly of Sudden Unexpected Death in Epilepsy Patients (SUDEP). Similarly, such cleaning can lead to morbidity and even mortality problems following anesthesia. If our assumption is correct, this understanding of the process of the problems' origin can lead to a method to remedy them by judicial supplement of the lost materials.

Percolation and tortuosity in heart-like cells.

In the last several years, quite a few papers on the joint question of transport, tortuosity and percolation have appeared in the literature, dealing with passage of miscellaneous liquids or electrical currents in different media. However, these methods have not been applied to the passage of action potential in heart fibrosis (HF), which is crucial for problems of heart arrhythmia, especially of atrial tachycardia and fibrillation. In this work we address the HF problem from these aspects. A cellular automaton model is used to analyze percolation and transport of a distributed-fibrosis inflicted heart-like tissue. Although based on a rather simple mathematical model, it leads to several important outcomes: (1) It is shown that, for a single wave front (as the one emanated by the heart's sinus node), the percolation of heart-like matrices is exactly similar to the forest fire case. (2) It is shown that, on the average, the shape of the transport (a question not dealt with in relation to forest fire, and deals with the delay of action potential when passing a fibrotic tissue) behaves like a Gaussian. (3) Moreover, it is shown that close to the percolation threshold the parameters of this Gaussian behave in a critical way. From the physical point of view, these three results are an important contribution to the general percolation investigation. The relevance of our results to cardiological issues, specifically to the question of reentry initiation, are discussed and it is shown that: (A) Without an ectopic source and under a mere sinus node operation, no arrhythmia is generated, and (B) A sufficiently high refractory period could prevent some reentry mechanisms, even in partially fibrotic heart tissue.

Explaining recent postictal epilepsy EEG results by the G-lymphatic clearance hypothesis.

Two recent postictal EEG measurements demonstrate somewhat conflicting results of epileptic behavior clearance in different brain parts. Both measurements observed two modes of seizure cessation, an abrupt and a gradual one, with slightly different statistics. No explanations were given for the appearance of these modes. Both measurements differ also in assessing the postictal brain activity or lack thereof, specifically the gamma activity. Using our G-Lymphatic clearance hypothesis, these results can be explained theoretically. The presence of two modes can be related to the order of ISF-CSF cleaning of brain parts. The reduced activity can be ascribed to neuronal ingredients deficiency brought about by the seizure related excess brain activity and by an over cleaning by the G-Lymphatic system.

Lyme carditis. Electrophysiologic and histopathologic study.

To further define the nature of Lyme carditis, electrophysiologic study and endomyocardial biopsy were performed in a patient with Lyme disease, whose principal cardiac manifestation was high-degree atrioventricular block. Intracardiac recording demonstrated supra-Hisian block and complete absence of an escape mechanism. Gallium 67 scanning demonstrated myocardial uptake, and right ventricular endomyocardial biopsy revealed active lymphocytic myocarditis. A structure compatible with a spirochetal organism was demonstrated in one biopsy specimen. It is concluded that Lyme disease can produce active myocarditis, as suggested by gallium 67 imaging and confirmed by endomyocardial biopsy. Furthermore, the presence of high-grade atrioventricular block in this disease requires aggressive management with temporary pacemaker and corticosteroid therapy.

Lack of ouabain effect on pacing-induced myocardial ischemia in patients with coronary artery disease.

Sixteen patients with significant two and three vessel coronary artery disease but without clinical congestive heart failure were studied during rapid atrial pacing before and after infusion of 0.015 mg/kg of ouabain. Seven patients with a decreased (less than 50 percent) ejection fraction and nine patients with a normal ejection fraction had a significant (P less than 0.05) increase in resting arterial systolic pressure after the administration of ouabain. However, resting values for coronary sinus flow, coronary vascular resistance, myocardial oxygen consumption and myocardial lactate extraction did not change significantly in either group. During pacing, patients with a decreased ejection fraction demonstrated more ischemia than patients with a normal ejection fraction; however, the administration of ouabain did not significantly alter pacing-related changes in coronary sinus flow, myocardial oxygen consumption, myocardial lactate extraction, ischemic electrocardiographic changes or onset of chest pain in either group. The administration of ouabain has a negligible effect on coronary hemodynamics, myocardial metabolism or clinical signs of ischemia in patients with coronary artery disease with normal or abnormal left ventricular function.

Rebinding and relaxation in the myoglobin pocket.

The infrared stretching bands of carboxymyoglobin (MbCO) and the rebinding of CO to Mb after photodissociation have been studied in the temperature range 10-300 K in a variety of solvents. Four stretching bands imply that MbCO can exist in four substates, A0-A3. The temperature dependences of the intensities of the four bands yield the relative binding enthalpies and and entropies. The integrated absorbances and pH dependences of the bands permit identification of the substates with the conformations observed in the X-ray data (Kuriyan et al., J. Mol. Biol. 192 (1986) 133). At low pH, A0 is hydrogen-bonded to His E7. The substates A0-A3 interconvert above about 180 K in a 75% glycerol/water solvent and above 270 K in buffered water. No major interconversion is seen at any temperature if MbCO is embedded in a solid polyvinyl alcohol matrix. The dependence of the transition on solvent characteristics is explained as a slaved glass transition. After photodissociation at low temperature the CO is in the heme pocket B. The resulting CO stretching bands which are identified as B substates are blue-shifted from those of the A substates. At 40 K, rebinding after flash photolysis has been studied in the Soret, the near-infrared, and the integrated A and B substates. All data lie on the same rebinding curve and demonstrate that rebinding is nonexponential in time from at least 100 ns to 100 ks. No evidence for discrete exponentials is found. Flash photolysis with monitoring in the infrared region shows four different pathways within the pocket B to the bound substates Ai. Rebinding in each of the four pathways B----A is nonexponential in time to at least 10 ks and the four pathways have different kinetics below 180 K. From the time and temperature dependence of the rebinding, activation enthalpy distributions g(HBA) and preexponentials ABA are extracted. No pumping from one A substate to another, or one B substate to another, is observed below the transition temperature of about 180 K. If MbCO is exposed to intense white light for 10-10(3) s before being fully photolyzed by a laser flash, the amplitude of the long-lived states increases. The effect is explained in terms of a hierarchy of substates and substate symmetry breaking. The characteristics of the CO stretching bands and of the rebinding processes in the heme pocket depend strongly on the external parameters of solvent, pH and pressure. This sensitivity suggests possible control mechanisms for protein reactions.

Pericardial cyst: an incidental finding.

Pericardial cysts are rare mediastinal cysts occurring with an incidence of 1 in 100, 000. Characteristically, they occur along the right border of the heart. Their size varies from 1.0 cm to 15 cm, and they are often asymptomatic. Patients with symptoms usually have atypical chest pain. In the case reported here, a 37-year-old man complained of nonproductive cough. Chest x-ray film revealed a pericardial cyst that appeared as a large echolucent unilocular mass along the left border of the heart. Diagnosis was confirmed with the use of both computed tomography and transthoracic echocardiography.

Time-periodic lattice of spiral pairs in excitable media.

The feasibility of a spiral-type solution, periodic both in time and in space, of a reaction-diffusion equation (specifically the FitzHugh-Nagumo system) in an excitable medium is numerically demonstrated. The solution consists of arrays of interacting spiral pairs, which repeatedly create by partial annihilation a system of residual portions (RPs). The latter behaves as a source to the next generation of the spiral-pair array. If basic (highest) translational symmetry is not conserved, pointwise perturbations, above a certain threshold, are shown to be able to destroy the pattern after a certain transient time by changing its symmetry. If the basic translational symmetry is preserved, such perturbations do not cause destruction unless occurring at the nearest vicinity of the RP site. Singular value decomposition methods are used to analyze the structure of the pattern, revealing the importance of the spiral pairs and the RPs.

Auxological evaluation in patients with a 22q11.2 microdeletion syndrome: normal prevalence of obesity and neonatal length and gender influence on body mass index evolution.

AIMS: To evaluate auxological parameters in children and adults with a 22q11.2 microdeletion syndrome (22q11.2 DS) and to compare prevalence of obesity to that in the French general population. METHODS: 102 patients with 22q11.2 DS (49 males, 53 females) were recruited from birth to adulthood through a reference center in southern France. RESULTS: Mean BMI Z score and mean height were normal (0.07 ± 1.49 SD, -0.87 ± 1.36 SDS, respectively). 16.1% of patients were overweight (including obese), 57% out of them being born small for gestational age for length versus 25% of non-overweight patients. During infancy, BMI increased in girls (+0.89 SD Z score). Childhood: 14.7% were overweight, prevalence similar to that of the in French children population. Adulthood: 19.2% were overweight. BMI Z scores were inversely correlated with neonatal length (p = 0.026) and female sex (p = 0.032) but positively associated with neonatal weight (p = 0.036). From analysis of neonatal data, 22q11.2 DS newborns were significantly shorter with regard to their weight (p < 0.01), even though mean neonatal measures were above -2 SDS. CONCLUSIONS: Our study did not find a higher prevalence of overweight in 22q11.2 DS to that in the French population. The BMI Z score was inversely correlated with neonatal length and female gender but positively associated with neonatal weight.