Intersectoral action for health: preventing psittacosis spread after one reported case

Zoonotic diseases are a significant health threat for humans and animals. To better understand the epidemiology, etiology, and pathology of infectious agents affecting humans and animals combined approaches are needed. Here we describe an epidemiological investigation conducted by physicians and veterinarians after a reported case of psittacosis. Upon admission suffering from respiratory distress syndrome in a hospital and with a history of bird contact, a female patient was serologically diagnosed with psittacosis. After the case notification, veterinarians were able to investigate the source of infection by detecting Chlamydia psittaci in her pet cockatiel. The bird was hospitalized and successfully treated. In addition, the establishment where the pet bird was purchased was traced and through molecular techniques other birds intended to be sold as pets tested positive for C. psittaci. As a result, sanitary measures were applied and the establishment then was closed down. The birds intended for the pet commerce were treated and retested with negative molecular results for C. psittaci, thus avoiding disease propagation. Reliable data about zoonotic diseases can only be generated through the application of multidisciplinary approaches which take into account the epidemiological factors and interactions of humans, animals and their environments as an integrated system

Intersectoral action for health: preventing psittacosis spread after one reported case.

Zoonotic diseases are a significant health threat for humans and animals. To better understand the epidemiology, etiology, and pathology of infectious agents affecting humans and animals combined approaches are needed. Here we describe an epidemiological investigation conducted by physicians and veterinarians after a reported case of psittacosis. Upon admission suffering from respiratory distress syndrome in a hospital and with a history of bird contact, a female patient was serologically diagnosed with psittacosis. After the case notification, veterinarians were able to investigate the source of infection by detecting Chlamydia psittaci in her pet cockatiel. The bird was hospitalized and successfully treated. In addition, the establishment where the pet bird was purchased was traced and through molecular techniques other birds intended to be sold as pets tested positive for C. psittaci. As a result, sanitary measures were applied and the establishment then was closed down. The birds intended for the pet commerce were treated and retested with negative molecular results for C. psittaci, thus avoiding disease propagation. Reliable data about zoonotic diseases can only be generated through the application of multidisciplinary approaches which take into account the epidemiological factors and interactions of humans, animals and their environments as an integrated system.

Joint scaling laws in functional and evolutionary categories in prokaryotic genomes.

We propose and study a class-expansion/innovation/loss model of genome evolution taking into account biological roles of genes and their constituent domains. In our model, numbers of genes in different functional categories are coupled to each other. For example, an increase in the number of metabolic enzymes in a genome is usually accompanied by addition of new transcription factors regulating these enzymes. Such coupling can be thought of as a proportional 'recipe' for genome composition of the type 'a spoonful of sugar for each egg yolk'. The model jointly reproduces two known empirical laws: the distribution of family sizes and the non-linear scaling of the number of genes in certain functional categories (e.g. transcription factors) with genome size. In addition, it allows us to derive a novel relation between the exponents characterizing these two scaling laws, establishing a direct quantitative connection between evolutionary and functional categories. It predicts that functional categories that grow faster-than-linearly with genome size to be characterized by flatter-than-average family size distributions. This relation is confirmed by our bioinformatics analysis of prokaryotic genomes. This proves that the joint quantitative trends of functional and evolutionary classes can be understood in terms of evolutionary growth with proportional recipes.

Mean-field methods in evolutionary duplication-innovation-loss models for the genome-level repertoire of protein domains.

We present a combined mean-field and simulation approach to different models describing the dynamics of classes formed by elements that can appear, disappear, or copy themselves. These models, related to a paradigm duplication-innovation model known as Chinese restaurant process, are devised to reproduce the scaling behavior observed in the genome-wide repertoire of protein domains of all known species. In view of these data, we discuss the qualitative and quantitative differences of the alternative model formulations, focusing in particular on the roles of element loss and of the specificity of empirical domain classes.

Minimal two-sphere model of the generation of fluid flow at low Reynolds numbers.

Locomotion and generation of flow at low Reynolds number are subject to severe limitations due to the irrelevance of inertia: the "scallop theorem" requires that the system have at least two degrees of freedom, which move in non-reciprocal fashion, i.e. breaking time-reversal symmetry. We show here that a minimal model consisting of just two spheres driven by harmonic potentials is capable of generating flow. In this pump system the two degrees of freedom are the mean and relative positions of the two spheres. We have performed and compared analytical predictions, numerical simulation and experiments, showing that a time-reversible drive is sufficient to induce flow.

Feedback topology and XOR-dynamics in Boolean networks with varying input structure.

We analyze a model of fixed in-degree random Boolean networks in which the fraction of input-receiving nodes is controlled by the parameter gamma. We investigate analytically and numerically the dynamics of graphs under a parallel XOR updating scheme. This scheme is interesting because it is accessible analytically and its phenomenology is at the same time under control and as rich as the one of general Boolean networks. We give analytical formulas for the dynamics on general graphs, showing that with a XOR-type evolution rule, dynamic features are direct consequences of the topological feedback structure, in analogy with the role of relevant components in Kauffman networks. Considering graphs with fixed in-degree, we characterize analytically and numerically the feedback regions using graph decimation algorithms (Leaf Removal). With varying gamma , this graph ensemble shows a phase transition that separates a treelike graph region from one in which feedback components emerge. Networks near the transition point have feedback components made of disjoint loops, in which each node has exactly one incoming and one outgoing link. Using this fact, we provide analytical estimates of the maximum period starting from topological considerations.

A comparative evolutionary study of transcription networks. The global role of feedback and hierachical structures.

We present a comparative analysis of large-scale topological and evolutionary properties of transcription networks in three species: the two distant bacteria E. coli and B. subtilis, and the yeast S. cerevisiae. The study focuses on the global aspects of feedback and hierarchy in transcriptional regulatory pathways. While confirming that gene duplication has a significant impact on the shaping of all the analyzed transcription networks, our results point to distinct trends between the bacteria, which display a hierarchical network structure with short transcription cascades, and yeast, which seems able to sustain a higher wiring complexity, including larger feedback, longer transcription cascades, and the combinatorial use of heterodimers made of duplicate transcription factors, absent in E. coli.

DIA-MCIS: an importance sampling network randomizer for network motif discovery and other topological observables in transcription networks.

MOTIVATION: Transcription networks, and other directed networks can be characterized by some topological observables (e.g. network motifs), that require a suitable randomized network ensemble, typically with the same degree sequences of the original ones. The commonly used algorithms sometimes have long convergence times, and sampling problems. We present here an alternative, based on a variant of the importance sampling Monte Carlo developed by (Chen et al.). AVAILABILITY: The algorithm is available at http://wwwteor.mi.infn.it/bassetti/downloads.html

Random networks tossing biased coins.

In statistical mechanical investigations of complex networks, it is useful to employ random graph ensembles as null models to compare with experimental realizations. Motivated by transcription networks, we present here a simple way to generate an ensemble of random directed graphs with asymptotically, scale-free out-degree and compact in-degree. Entries in each row of the adjacency matrix are set to 0 or 1 according to the toss of a biased coin, with a chosen probability distribution for the biases. This defines a quick and simple algorithm, which yields good results already for graphs of size n approximately 100. Perhaps more importantly, many of the relevant observables are accessible analytically, improving upon previous estimates for similar graphs. The technique is easily generalizable to different kinds of graphs.

Hierarchy and feedback in the evolution of the Escherichia coli transcription network.

The Escherichia coli transcription network has an essentially feedforward structure, with abundant feedback at the level of self-regulations. Here, we investigate how these properties emerged during evolution. An assessment of the role of gene duplication based on protein domain architecture shows that (i) transcriptional autoregulators have mostly arisen through duplication, whereas (ii) the expected feedback loops stemming from their initial cross-regulation are strongly selected against. This requires a divergent coevolution of the transcription factor DNA-binding sites and their respective DNA cis-regulatory regions. Moreover, we find that the network tends to grow by expansion of the existing hierarchical layers of computation, rather than by addition of new layers. We also argue that rewiring of regulatory links due to mutation/selection of novel transcription factor/DNA binding interactions appears not to significantly affect the network global hierarchy, and that horizontally transferred genes are mainly added at the bottom, as new target nodes. These findings highlight the important evolutionary roles of both duplication and selective deletion of cross-talks between autoregulators in the emergence of the hierarchical transcription network of E. coli.

Logic backbone of a transcription network.

A great part of the effort in the study of coarse-grained models of transcription networks concentrates on their dynamical features. In this Letter, we consider their equilibrium properties, showing that the backbone underlying the dynamic descriptions is an optimization problem. It involves N variables, the gene expression levels, and M constraints, the effects of transcriptional regulation. In the case of Boolean variables and constraints, we investigate the structure of the solutions and derive phase diagrams. Notably, the model exhibits a connectivity transition between a regime of simple gene control, where the input genes control O(1) other genes, and a regime of complex control, where some core input genes control O(N) others.

Metachronal waves for deterministic switching two-state oscillators with hydrodynamic interaction.

We employ a model system, called rowers, as a generic physical framework to define the problem of the coordinated motion of cilia (the metachronal wave) as a far from equilibrium process. Rowers are active (two-state) oscillators in a low Reynolds number fluid, and interact solely through the forces of hydrodynamic origin. In this work, we consider the case of fully deterministic dynamics, find analytical solutions of the equation of motion in the long-wavelength (continuum) limit, and investigate numerically the short-wavelength limit. We prove the existence of metachronal waves below a characteristic wavelength. Such waves are unstable and become stable only if the sign of the coupling is reversed. We also find that with normal hydrodynamic interaction, the metachronal pattern has the form of stable trains of traveling wave packets sustained by the onset of anti-coordinated beating of consecutive rowers.

Encefalopatia hipertensiva associada a estado de mal epiléptico de repetição: relato de caso / Hypertensive encephalopathy associated to repetitive seizures: case report

Criança de cinco anos, feminina, branca, com história de oito internamentos nos últimos dois meses por crises convulsivas caracterizadas por vômitos, perda de consciência e clonias em hemicorpo direito. No exame físico, verificou-se hipertensão arterial grave (270/140 mmHg). Os estudos de neuroimagem (tomografia computadorizada e ressonância magnética) revelaram extensas áreas hipodensas, sugerindo edema cerebral. A arteriografia renal mostrou estenose da artéria renal direita, determinando a etiologia da hipertensão arterial. Com o controle da hipertensão, após a nefrectomia, houve reversão completa dos sintomas, assim como das anomalias de imagem.