Mindin/F-spondin Family: Novel ECM Proteins Expressed in the Zebrafish Embryonic Axis

AbstractF-spondin is a secreted protein expressed at high levels by the floor plate cells. The C-terminal half of the protein contains six thrombospondin type 1 repeats, while the N-terminal half exhibited virtually no similarity to any other protein until recently, when aDrosophilagene termedM-spondinwas cloned; its product was found to share two conserved domains with the N-terminal half of F-spondin. We report the molecular cloning of four zebrafish genes encoding secreted proteins with these conserved domains. Two are zebrafish homologs ofF-spondin,while the other two, termedmindin1andmindin2,encode mutually related novel proteins, which are more related to theDrosophilaM-spondin than to F-spondin. During embryonic development, all four genes are expressed in the floor plate cells. In addition to the floor plate,mindin1is expressed in the hypochord cells, whilemindin2is expressed in the sclerotome cells. When ectopically expressed, Mindin proteins selectively accumulate in the basal lamina, suggesting that Mindins are extracellular matrix (ECM) proteins with high affinity to the basal lamina. We also report the spatial distribution of one of the F-spondin proteins, F-spondin2. F-spondin2 is localized to the thread-like structure in the central canal of the spinal cord, which is likely to correspond to Reissner's fiber known to be present in the vertebrate phylum. In summary, our study has defined a novel gene family of ECM molecules in the vertebrate, all of which may potentially be involved in development of the midline structure

A noise-driven attractor switching device

Problems with artificial neural networks originate from their deterministic nature and inevitable prior learnings, resulting in inadequate adaptability against unpredictable, abrupt environmental change. Here we show that a stochastically excitable threshold unit can be utilized by these systems to partially overcome the environmental change. Using an excitable threshold system, attractors were created that represent quasi-equilibrium states into which a system settles until disrupted by environmental change. Furthermore, noise-driven attractor stabilization and switching were embodied by inhibitory connections. Noise works as a power source to stabilize and switch attractors, and endows the system with hysteresis behavior that resembles that of stereopsis and binocular rivalry in the human visual cortex. A canonical model of the ring network with inhibitory connections composed of class 1 neurons also shows properties that are similar to the simple threshold system.Comment: 9 pages, 2 tables, and 6 figures. will appear in Phy.Rev.E, vol.79, issue

Cooperative Dynamics of an Artificial Stochastic Resonant System

We have investigated cooperative dynamics of an artificial stochastic resonant system, which is a recurrent ring connection of neuron-like signal transducers (NST) based on stochastic resonance (SR), using electronic circuit experiments. The ring showed quasi-periodic, tunable oscillation driven by only noise. An oscillation coherently amplified by noise demonstrated that SR may lead to unusual oscillation features. Furthermore, we found that the ring showed synchronized oscillation in a chain network composed of multiple rings. Our results suggest that basic functions (oscillation and synchronization) that may be used in the central pattern generator of biological system are induced by collective integration of the NST element.Comment: 13 pages, 4 figure

Pancreatic β Cell–specific Expression of Thioredoxin, an Antioxidative and Antiapoptotic Protein, Prevents Autoimmune and Streptozotocin-induced Diabetes

The cytotoxicity of reactive oxygen intermediates (ROIs) has been implicated in the destruction of pancreatic β cells in insulin-dependent diabetes mellitus (IDDM). Thioredoxin (TRX), a redox (reduction/oxidation)-active protein, has recently been shown to protect cells from oxidative stress and apoptosis. To elucidate the roles of oxidative stress in the development of autoimmune diabetes in vivo, we produced nonobese diabetic transgenic mice that overexpress TRX in their pancreatic β cells. In these transgenic mice, the incidence of diabetes was markedly reduced, whereas the development of insulitis was not prevented. Moreover, induction of diabetes by streptozotocin, an ROI-generating agent, was also attenuated by TRX overexpression in β cells. This is the first direct demonstration that an antioxidative and antiapoptotic protein protects β cells in vivo against both autoimmune and drug-induced diabetes. Our results strongly suggest that oxidative stress plays an essential role in the destruction of β cells by infiltrating inflammatory cells in IDDM

Next-to-Minimal Supersymmetric Standard Model with the Gauge Mediation of Supersymmetry Breaking

We study the Next-to-Minimal Supersymmetric Standard Model (NMSSM) as the simplest candidate solution to the $\mu$-problem in the context of the gauge mediation of supersymmetry breaking (GMSB). We first review various proposals to solve the $\mu$-problem in models with the GMSB. We find none of them entirely satisfactory and point out that many of the scenarios still lack quantitative studies, and motivate the NMSSM as the simplest possible solution. We then study the situation in the Minimal Supersymmetric Standard Model (MSSM) with the GMSB and find that an order 10% cancellation is necessary between the $\mu$-parameter and the soft SUSY-breaking parameters to correctly reproduce $M_Z$. Unfortunately, the NMSSM does not to give a phenomenologically viable solution to the $\mu$-problem. We present quantitative arguments which apply both for the low-energy and high-energy GMSB and prove that the NMSSM does not work for either case. Possible modifications to the NMSSM are then discussed. The NMSSM with additional vector-like quarks works phenomenologically, but requires an order a few percent cancellation among parameters. We point out that this cancellation has the same origin as the cancellation required in the MSSM.Comment: 36 pages, LaTeX, epsf.sty, 5 figures, references added, comments on some other papers based on our misundestanding corrected, none of our results change

Multiple Translocation of the AVR-Pita Effector Gene among Chromosomes of the Rice Blast Fungus Magnaporthe oryzae and Related Species

Magnaporthe oryzae is the causal agent of rice blast disease, a devastating problem worldwide. This fungus has caused breakdown of resistance conferred by newly developed commercial cultivars. To address how the rice blast fungus adapts itself to new resistance genes so quickly, we examined chromosomal locations of AVR-Pita, a subtelomeric gene family corresponding to the Pita resistance gene, in various isolates of M. oryzae (including wheat and millet pathogens) and its related species. We found that AVR-Pita (AVR-Pita1 and AVR-Pita2) is highly variable in its genome location, occurring in chromosomes 1, 3, 4, 5, 6, 7, and supernumerary chromosomes, particularly in rice-infecting isolates. When expressed in M. oryzae, most of the AVR-Pita homologs could elicit Pita-mediated resistance, even those from non-rice isolates. AVR-Pita was flanked by a retrotransposon, which presumably contributed to its multiple translocation across the genome. On the other hand, family member AVR-Pita3, which lacks avirulence activity, was stably located on chromosome 7 in a vast majority of isolates. These results suggest that the diversification in genome location of AVR-Pita in the rice isolates is a consequence of recognition by Pita in rice. We propose a model that the multiple translocation of AVR-Pita may be associated with its frequent loss and recovery mediated by its transfer among individuals in asexual populations. This model implies that the high mobility of AVR-Pita is a key mechanism accounting for the rapid adaptation toward Pita. Dynamic adaptation of some fungal plant pathogens may be achieved by deletion and recovery of avirulence genes using a population as a unit of adaptation

A comparative assessment of transit technologies: bus x personal rapid transit (PRT)

Este trabalho apresenta uma metodologia para avaliação de novas tecnologias de transporte público urbano. O objetivo é aplicar esta metodologia para tornar possível a comparação entre diferentes tecnologias para o transporte público. Este trabalho também considera ainda a introdução de uma nova tecnologia em uma cidade média brasileira. Trata-se do transporte público individualizado (TPI) ou personal rapid transit (PRT), como potencial substituto do ônibus. O TPI, que é uma tecnologia pouco conhecida, porém tem um potencial a ser explorado, já que possui características de transporte individual e ao mesmo tempo, é um serviço de transporte público. A metodologia consiste em duas etapas: a primeira etapa emprega a técnica conhecida como analytic hierarchy process (AHP), que já foi utilizada para avaliar projetos de transporte que envolvem atributos de diferentes naturezas e que são de difícil comparação utilizando outras técnicas. A estrutura desenvolvida contemplou a seleção de critérios, a determinação dos pesos dos critérios, o levantamento dos dados de cada tecnologia para comparação, a comparação dos dados das tecnologias dentro de cada critério e, por fim, a determinação da tecnologia mais adequada. Dois grupos de avaliadores foram considerados: pesquisadores especialistas em transporte público e usuários. A segunda etapa consiste em comparar diretamente o desempenho operacional das tecnologias. Foram comparados o tempo de atendimento, a capacidade máxima de atendimento, o tempo de viagem por passageiro e pelo sistema. A avaliação da primeira etapa deu ao TPI uma ligeira vantagem para os dois grupos, o que pode evidenciar a necessidade de se modificar o conceito de transporte público urbano. A avaliação para a segunda etapa demonstrou que o TPI atenderia a demanda numa cidade média com qualidade superior ao ônibus, porém a capacidade de atendimento, na forma apresentada, é inferior ao ônibus. Com base nos resultados, o TPI surge como uma alternativa interessante ao ônibus, porém sofre restrições por conta de seu alto custo de investimento.This work discusses a methodology for the appraisal of new technologies of urban public transportation. The objective is to apply such a methodology to make possible a comparison of different technologies for public transportation. This work also considers the introduction of the personal rapid transit (PRT) in a brazilian medium-sized city as a potential candidate to replace the traditional bus technology. Although not yet a widespread alternative, PRT is a promising transportation technology, given its characteristics of individual transportation and, at the same time, the status of public service. The methodology consists in two steps: the first one uses the well-known technique named analytic hierarchy process (AHP), which has already been extensively used to assess transportation projects that involve different attributes and that cannot be easily compared with other techniques. The framework developed had the following phases: selection of criteria, identification of criteria weights, identification and comparison of the characteristics of each technology under comparison, and determination of the best alternative. Two groups of evaluators were considered in the analysis: experts and regular users of urban public transportation. The second phase is a direct comparison of the operational performance of the technologies under analysis. The analysis was done through the comparison of services times, maximum service capacity, and travel times per passenger and in the entire system. The final outcome of the evaluation has shown a slight advantage to PRT for both groups, what can suggest the need for changing the current view of urban public transportation. The second part of the evaluation has demonstrated that PRT could serve the demand of a medium-sized city with a higher level of service, although with capacity constraints in the case considered. The results suggest that PRT can be an interesting alternative to bus, if not limited by the very high investment costs