Stochastic dynamics of a finite-size spiking neural network

We present a simple Markov model of spiking neural dynamics that can be analytically solved to characterize the stochastic dynamics of a finite-size spiking neural network. We give closed-form estimates for the equilibrium distribution, mean rate, variance and autocorrelation function of the network activity. The model is applicable to any network where the probability of firing of a neuron in the network only depends on the number of neurons that fired in a previous temporal epoch. Networks with statistically homogeneous connectivity and membrane and synaptic time constants that are not excessively long could satisfy these conditions. Our model completely accounts for the size of the network and correlations in the firing activity. It also allows us to examine how the network dynamics can deviate from mean-field theory. We show that the model and solutions are applicable to spiking neural networks in biophysically plausible parameter regimes

Spontaneous Dynamics of Asymmetric Random Recurrent Spiking Neural Networks

We study in this paper the effect of an unique initial stimulation on random recurrent networks of leaky integrate and fire neurons. Indeed given a stochastic connectivity this so-called spontaneous mode exhibits various non trivial dynamics. This study brings forward a mathematical formalism that allows us to examine the variability of the afterward dynamics according to the parameters of the weight distribution. Provided independence hypothesis (e.g. in the case of very large networks) we are able to compute the average number of neurons that fire at a given time -- the spiking activity. In accordance with numerical simulations, we prove that this spiking activity reaches a steady-state, we characterize this steady-state and explore the transients.Comment: 28 pages, 7 figure

Endovascular retrieval of two migrated venous stents by means of balloon catheters

AbstractThe usefulness of vascular stenting was demonstrated in both arterial and venous applications to restore patency and improve suboptimal results after percutaneous transluminal angioplasty. Dislodgment of venous stents with an embolization into the right cavities or the pulmonary artery, however, is one of the most feared complications of this procedure. Percutaneous removal of these migrated stents is an appealing method of replacing more invasive operative intervention with cardiopulmonary bypass, which may be very hazardous in these often severely ill patients. We describe the cases of two patients with stents that migrated into the right ventricle and the pulmonary artery. In one patient, we were able to successfully remove these stents by using an angioplasty balloon with an operative extraction from the iliac vein, thereby obviating the need for a major operative procedure. (J Vasc Surg 1998;28:541-6.

How Gibbs distributions may naturally arise from synaptic adaptation mechanisms. A model-based argumentation

This paper addresses two questions in the context of neuronal networks dynamics, using methods from dynamical systems theory and statistical physics: (i) How to characterize the statistical properties of sequences of action potentials ("spike trains") produced by neuronal networks ? and; (ii) what are the effects of synaptic plasticity on these statistics ? We introduce a framework in which spike trains are associated to a coding of membrane potential trajectories, and actually, constitute a symbolic coding in important explicit examples (the so-called gIF models). On this basis, we use the thermodynamic formalism from ergodic theory to show how Gibbs distributions are natural probability measures to describe the statistics of spike trains, given the empirical averages of prescribed quantities. As a second result, we show that Gibbs distributions naturally arise when considering "slow" synaptic plasticity rules where the characteristic time for synapse adaptation is quite longer than the characteristic time for neurons dynamics.Comment: 39 pages, 3 figure

Synopsis of the pelidnotine scarabs (Coleoptera, Scarabaeidae, Rutelinae, Rutelini) and annotated catalog of the species and subspecies

The pelidnotine scarabs (Scarabaeidae: Rutelinae: Rutelini) are a speciose, paraphyletic assemblage of beetles that includes spectacular metallic species (“jewel scarabs”) as well as species that are ecologically important as herbivores, pollinators, and bioindicators. These beetles suffer from a complicated nomenclatural history, due primarily to 20th century taxonomic and nomenclatural errors. We review the taxonomic history of the pelidnotine scarabs, present a provisional key to genera with overviews of all genera, and synthesize a catalog of all taxa with synonyms, distributional data, type specimen information, and 107 images of exemplar species. As a result of our research, the pelidnotine leaf chafers (a paraphyletic group) include 27 (26 extant and 1 extinct) genera and 420 valid species and subspecies (419 extant and 1 extinct). Our research makes biodiversity research on this group tractable and accessible, thus setting the stage for future studies that address evolutionary and ecological trends. Based on our research, 1 new species is described, 1 new generic synonym and 12 new species synonyms are proposed, 11 new lectotypes and 1 new neotype are designated, many new or revised nomenclatural combinations, and many unavailable names are presented. The following taxonomic changes are made: New generic synonym: The genus Heteropelidnota Ohaus, 1912 is a new junior synonym of Pelidnota MacLeay, 1819. New species synonyms: Plusiotis adelaida pavonacea Casey, 1915 is a syn. n. of Chrysina adelaida (Hope, 1841); Odontognathus gounellei Ohaus, 1908 is a revised synonym of Pelidnota ebenina (Blanchard, 1842); Pelidnota francoisgenieri Moore & Jameson, 2013 is a syn. n. of Pelidnota punctata (Linnaeus, 1758); Pelidnota genieri Soula, 2009 is a syn. n. of Pelidnota punctata (Linnaeus, 1758); Pelidnota lutea (Olivier, 1758) is a revised synonym of Pelidnota punctata (Linnaeus, 1758); Pelidnota (Pelidnota) texensis Casey, 1915 is a revised synonym of Pelidnota punctata (Linnaeus, 1758); Pelidnota (Strigidia) zikani (Ohaus, 1922) is a revised synonym of Pelidnota tibialis tibialis Burmeister, 1844; Pelidnota ludovici Ohaus, 1905 is a syn. n. of Pelidnota burmeisteri tricolor Nonfried, 1894; Rutela fulvipennis Germar, 1824 is syn. n. of Pelidnota cuprea (Germar, 1824); Pelidnota pulchella blanda Burmeister, 1844 is a syn. n. of Pelidnota pulchella pulchella (Kirby, 1819); Pelidnota pulchella scapularis Burmeister, 1844 is a syn. n. of Pelidnota pulchella pulchella (Kirby, 1819); Pelidnota xanthogramma Perty, 1830 is a syn. n. of Pelidnota pulchella pulchella (Kirby, 1819). New or revised statuses: Pelidnota fabricelavalettei Soula, 2009, revised status, is considered a species; Pelidnota rioensis Soula, 2009, stat. n., is considered a species; Pelidnota semiaurata semiaurata Burmeister, 1844, stat. rev., is considered a subspecies. New or comb. rev. and revised status: Plusiotis guaymi Curoe, 2001 is formally transferred to the genus Chrysina (C. guaymi (Curoe, 2001), comb. n.); Plusiotis transvolcanica Morón & Nogueira, 2016 is transferred to the genus Chrysina (C. transvolcanica (Morón & Nogueira, 2016), comb. n.). Heteropelidnota kuhnti Ohaus, 1912 is transferred to the genus Pelidnota (P. kuhnti (Ohaus, 1912), comb. n.); Odontognathus riedeli Ohaus, 1905 is considered a subspecies of Pelidnota rubripennis Burmeister, 1844 (Pelidnota rubripennis riedeli (Ohaus, 1905), revised status and comb. rev.); Pelidnota (Strigidia) acutipennis (F. Bates, 1904) is transferred to the genus Sorocha (Sorocha acutipennis (F. Bates, 1904), comb. rev.); Pelidnota (Odontognathus) nadiae Martínez, 1978 is transferred to the genus Sorocha (Sorocha nadiae (Martínez, 1978), comb. rev.); Pelidnota (Ganonota) plicipennis Ohaus, 1934 is transferred to the genus Sorocha (Sorocha plicipennis (Ohaus, 1934), comb. rev.); Pelidnota similis Ohaus, 1908 is transferred to the genus Sorocha (Sorocha similis (Ohaus, 1908), comb. rev.); Pelidnota (Ganonota) yungana Ohaus, 1934 is transferred to Sorocha (Sorocha yungana (Ohaus, 1934), comb. rev.); Pelidnota malyi Soula, 2010: 58, revised status; Xenopelidnota anomala porioni Chalumeau, 1985, revised subspecies status. To stabilize the classification of the group, a neotype is designated for the following species: Pelidnota thiliezi Soula, 2009. Lectotypes are designated for the following names (given in their original combinations): Pelidnota brevicollis Casey, 1915, Pelidnota brevis Casey, 1915, Pelidnota debiliceps Casey, 1915, Pelidnota hudsonica Casey, 1915, Pelidnota oblonga Casey, 1915, Pelidnota pallidipes Casey, 1915, Pelidnota ponderella Casey, 1915, Pelidnota strenua Casey, 1915, Pelidnota tarsalis Casey, 1915, Pelidnota texensis Casey, 1915, and Scarabaeus punctatus Linnaeus, 1758. The following published infrasubspecific names are unavailable per ICZN Article 45.6.1: Pelidnota (Odontognathus) cuprea var. coerulea Ohaus, 1913; Pelidnota (Odontognathus) cuprea var. rufoviolacea Ohaus, 1913; Pelidnota (Odontognathus) cuprea var. nigrocoerulea Ohaus, 1913; Pelidnota pulchella var. fulvopunctata Ohaus, 1913; Pelidnota pulchella var. sellata Ohaus, 1913; Pelidnota pulchella var. reducta Ohaus, 1913; Pelidnota unicolor var. infuscata Ohaus, 1913. The following published species name is unavailable per ICZN Article 11.5: Neopatatra synonyma Moore & Jameson, 2013. The following published species name is unavailable per application of ICZN Article 16.1: Parhoplognathus rubripennis Soula, 2008. Synopsis of the pelidnotine scarabs (Coleoptera, Scarabaeidae, Rutelinae, Rutelini) 3 The following published species name is unavailable per application of ICZN Article 16.4.1: Strigidia testaceovirens argentinica Soula, 2006, Pelidnota (Strigidia) testaceovirens argentinica (Soula, 2006), and Pelidnota testaceovirens argentinica (Soula, 2006). The following published species names are unavailable per application of ICZN Article 16.4.2: Homonyx digennaroi Soula, 2010; Homonyx lecourti Soula, 2010; Homonyx mulliei Soula, 2010; Homonyx simoensi Soula, 2010; Homonyx wagneri Soula, 2010; Homonyx zovii Demez & Soula, 2011; Pelidnota arnaudi Soula, 2009; Pelidnota brusteli Soula, 2010; Pelidnota chalcothorax septentrionalis Soula, 2009; Pelidnota degallieri Soula, 2010; Pelidnota lavalettei Soula, 2008; Pelidnota lavalettei Soula, 2009; Pelidnota dieteri Soula, 2011; Strigidia gracilis decaensi Soula, 2008, Pelidnota (Strigidia) gracilis decaensi (Soula, 2008), and Pelidnota gracilis decaensi (Soula, 2008); Pelidnota halleri Demez & Soula, 2011; Pelidnota injantepalominoi Demez & Soula, 2011; Pelidnota kucerai Soula, 2009; Pelidnota malyi Soula, 2010: 36-37; Pelidnota mezai Soula, 2009; Pelidnota polita darienensis Soula, 2009; Pelidnota polita orozcoi Soula, 2009; Pelidnota polita pittieri Soula, 2009; Pelidnota punctulata decolombia Soula, 2009; Pelidnota punctulata venezolana Soula, 2009; Pelidnota raingeardi Soula, 2009; Pelidnota schneideri Soula, 2010; Pelidnota simoensi Soula, 2009; Pelidnota unicolor subandina Soula, 2009; Sorocha carloti Demez & Soula, 2011; Sorocha castroi Soula, 2008; Sorocha fravali Soula, 2011; Sorocha jeanmaurettei Demez & Soula, 2011; Sorocha yelamosi Soula, 2011; Xenopelidnota bolivari Soula, 2009; Xenopelidnota pittieri pittieri Soula, 2009. Due to unavailability of the name Pseudogeniates cordobaensis Soula 2009, we describe the species as intentionally new (Pseudogeniates cordobaensis Moore, Jameson, Garner, Audibert, Smith, and Seidel, sp. n.)

Cellular localization, accumulation and trafficking of double-walled carbon nanotubes in human prostate cancer cells

Carbon nanotubes (CNTs) are at present being considered as potential nanovectors with the ability to deliver therapeutic cargoes into living cells. Previous studies established the ability of CNTs to enter cells and their therapeutic utility, but an appreciation of global intracellular trafficking associated with their cellular distribution has yet to be described. Despite the many aspects of the uptake mechanism of CNTs being studied, only a few studies have investigated internalization and fate of CNTs inside cells in detail. In the present study, intracellular localization and trafficking of RNA-wrapped, oxidized double-walled CNTs (oxDWNT–RNA) is presented. Fixed cells, previously exposed to oxDWNT–RNA, were subjected to immunocytochemical analysis using antibodies specific to proteins implicated in endocytosis; moreover cell compartment markers and pharmacological inhibitory conditions were also employed in this study. Our results revealed that an endocytic pathway is involved in the internalization of oxDWNT–RNA. The nanotubes were found in clathrin-coated vesicles, after which they appear to be sorted in early endosomes, followed by vesicular maturation, become located in lysosomes. Furthermore, we observed co-localization of oxDWNT–RNA with the small GTP-binding protein (Rab 11), involved in their recycling back to the plasma membrane via endosomes from the trans-golgi network

Epidemiology and clinical features of vivax malaria imported to Europe: Sentinel surveillance data from TropNetEurop

BACKGROUND: Plasmodium vivax is the second most common species among malaria patients diagnosed in Europe, but epidemiological and clinical data on imported P. vivax malaria are limited. The TropNetEurop surveillance network has monitored the importation of vivax malaria into Europe since 1999. OBJECTIVES: To present epidemiological and clinical data on imported P. vivax malaria collected at European level. MATERIAL AND METHODS: Data of primary cases of P. vivax malaria reported between January 1999 and September 2003 were analysed, focusing on disease frequency, patient characteristics, place of infection, course of disease, treatment and differences between network-member countries. RESULTS: Within the surveillance period 4,801 cases of imported malaria were reported. 618 (12.9%) were attributed to P. vivax. European travellers and immigrants were the largest patient groups, but their proportion varied among the reporting countries. The main regions of infection in descending order were the Indian subcontinent, Indonesia, South America and Western and Eastern Africa, as a group accounting for more than 60% of the cases. Regular use of malaria chemoprophylaxis was reported by 118 patients. With 86 (inter-quartile range 41–158) versus 31 days (inter-quartile range 4–133) the median symptom onset was significantly delayed in patients with chemoprophylaxis (p < 0.0001). Common complaints were fever, headache, fatigue, and musculo-skeletal symptoms. All patients survived and severe clinical complications were rare. Hospitalization was provided for 60% and primaquine treatment administered to 83.8% of the patients, but frequencies varied strongly among reporting countries. CONCLUSIONS: TropNetEurop data can contribute to the harmonization of European treatment policies

A stochastic automaton shows how enzyme assemblies may contribute to metabolic efficiency

<p>Abstract</p> <p>Background</p> <p>The advantages of grouping enzymes into metabolons and into higher order structures have long been debated. To quantify these advantages, we have developed a stochastic automaton that allows experiments to be performed in a virtual bacterium with both a membrane and a cytoplasm. We have investigated the general case of transport and metabolism as inspired by the phosphoenolpyruvate:sugar phosphotransferase system (PTS) for glucose importation and by glycolysis.</p> <p>Results</p> <p>We show that PTS and glycolytic metabolons can increase production of pyruvate eightfold at low concentrations of phosphoenolpyruvate. A fourfold increase in the numbers of enzyme EI led to a 40% increase in pyruvate production, similar to that observed <it>in vivo </it>in the presence of glucose. Although little improvement resulted from the assembly of metabolons into a hyperstructure, such assembly can generate gradients of metabolites and signaling molecules.</p> <p>Conclusion</p> <p><it>in silico </it>experiments may be performed successfully using stochastic automata such as HSIM (Hyperstructure Simulator) to help answer fundamental questions in metabolism about the properties of molecular assemblies and to devise strategies to modify such assemblies for biotechnological ends.</p