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PubMed1992

Medical Ethics Resource Network of Michigan: development of a statewide ethics network.

The Medical Ethics Resource Network (MERN) of Michigan has, over approximately 5 years, become a viable organization for disseminating educational information and raising the general standard of ethics discussion in a variety of institutional settings. This article reviews the history of the network's development, with special emphasis upon features that may suggest useful strategies for other networks now under formation.

Administrative Personnel↗

PubMed2001

Attractive periodic sets in discrete-time recurrent networks (with emphasis on fixed-point stability and bifurcations in two-neuron networks).

We perform a detailed fixed-point analysis of two-unit recurrent neural networks with sigmoid-shaped transfer functions. Using geometrical arguments in the space of transfer function derivatives, we partition the network state-space into distinct regions corresponding to stability types of the fixed points. Unlike in the previous studies, we do not assume any special form of connectivity pattern between the neurons, and all free parameters are allowed to vary. We also prove that when both neurons have excitatory self-connections and the mutual interaction pattern is the same (i.e., the neurons mutually inhibit or excite themselves), new attractive fixed points are created through the saddle-node bifurcation. Finally, for an N-neuron recurrent network, we give lower bounds on the rate of convergence of attractive periodic points toward the saturation values of neuron activations, as the absolute values of connection weights grow.

Mathematics↗

PubMed1996

Binary-oscillator networks: bridging a gap between experimental and abstract modeling of neural networks.

This paper proposes a simplified oscillator model, called binary-oscillator, and develops a class of neural network models having binary-oscillators as basic units. The binary-oscillator has a binary dynamic variable v = +/- 1 modeling the "membrane potential" of a neuron, and due to the presence of a "slow current" (as in a classical relaxation-oscillator) it can oscillate between two states. The purpose of the simplification is to enable abstract algorithmic study on the dynamics of oscillator networks. A binary-oscillator network is formally analogous to a system of stochastic binary spins (atomic magnets) in statistical mechanics.

Algorithms↗

PubMed1995

Secure and protected network connection between medical and external networks.

Internal and world-wide communication, access to medical databases, and information services are essential demands in the science of medicine not only for research, but also for improving patient care. A network connection between the medical network of the Erlangen University Hospital and other international networks was examined as a concept within the scope of a Erlangen Hospital Communication System (EKKS) project and tested with an actual installation.

Computer Communication Networks↗

PubMed1997

The emerging infections network: a new venture for the Infectious Diseases Society of America. Executive Committee of the Infectious Diseases Society of America Emerging Infections Network.

The Infectious Diseases Society of America (IDSA), in cooperation with the Centers for Disease Control and Prevention, has launched an Emerging Infections Network (EIN). This network of infectious diseases consultants was conceived as a sentinel system to monitor new or resurgent infectious diseases in a way that would complement other public health surveillance efforts. A pilot study with 169 participants recruited from 32 of the IDSA's state and regional societies confirmed the feasibility and potential value of this network. More than 300 infectious diseases consultants are currently participating in the IDSA EIN. Future plans include aggressive probing for clinical experiences that indicate or suggest the presence of emerging infections, initiation of prospective studies for selected infectious diseases, and other activities designed both to benefit consultants in infectious diseases and to make use of their services.

Communicable Disease Control↗

PubMed2005

Phenotype analysis using network motifs derived from changes in regulatory network dynamics.

The intrinsic dynamic response of a transcriptional regulatory network depends directly on molecular interactions in the cellular transcription, translation, and degradation machineries. These interactions can be incorporated into dynamic mathematical models of the biochemical system using the biophysical relationship with the model parameters. Modifications of such interactions bring changes to the biological behavior of the cells, and therefore, many normal and pathological cellular states depend on them. It is important for analysis, prediction, diagnosis, and treatment of cellular function to have an experimentally derived model with parameters that adequately represent the molecular interactions of interest. Finding the model and parameters of a transcriptional regulatory network is a difficult task that has been approached at different levels and with different techniques. We develop here a new analysis method (based on previous work on network inference, modeling, and parameter identification) that finds the most changed parameters from yeast oligonucleotide microarray expression patterns in cases where a phenotype difference exists between two samples. We then relate and examine the changed parameters with their associated genes, corresponding genetic functional categories, and particular subnetworks and connectivities. The biophysical bases for these changes are also identified by studying the relationship of the changed parameters with the transcription, translation, and degradation mechanisms. The method is improved to cases where there are two or more transcription factors influencing transcription, and a statistical analysis is performed to give a measurement of the uniqueness and robustness of the parameter fit.

Algorithms↗

PubMed1993

Cancer patients and their network: the meaning of the social network and social interactions for quality of life.

A lot of research is carried out on the subject of social relations and quality of life. One should find at least some indication for an association between the social environment and quality of life of cancer patients; will interventions be appropriate and well-considered? But until now, less has been known about the association between the social network of cancer patients and their quality of life. In this study, the way in which the patients' network can effect their quality of life is examined. Two patient groups are distinguished: a group of cancer patients recently treated for their cancer by surgery and a group treated by chemotherapy (n = 108 and n = 109) and these are compared with a disease-free group of cancer patients (n = 192). Although an association between network, social relations and quality of life is found, only a small part of the variation in quality of life can be explained by this social component. It seems that the cancer itself and the cancer treatment mainly affect the patients' quality of life and that the impact of the social environment is less significant.

Cross-Sectional Studies↗

PubMed2006

[The competence network for congenital heart defects. Networking instead of isolated efforts for optimized research and care].

Congenital heart defects (CHD) are the most common congenital malformation; there is no clearly defined clinical picture. Although, thanks to medical progress, most of those affected survive into adulthood, they remain chronically ill throughout their lives and require specific care. By enabling nationwide cooperation and interdisciplinary research, the Competence Network for Congenital Heart Defects can provide and optimize this care. Clinical studies concerning clinical manifestations and recent diagnostic and treatment options can make use of the collected data. Being the core project of the Network, the National Register for congenital heart defects (registered association) registers all patients with a CHD throughout Germany. This data provides a basis for epidemiologic studies concerning quality of life and psychosocial aspects. Thus, integral care and swift transfer of knowledge between science and practice can be achieved. Meanwhile, pediatric guidelines could be developed and raised to S2 level. Additionally, the Register's results allow an assessment of the present situation of cardiac malformations, which is to be further evaluated in current studies. Particular attention is paid to the prevalence of CHD and adult patients' needs. In the long term, the concept of integrated care, and especially the idea of multidisciplinarity, is to be realized within the scope of a "health care database". All in all, the Competence Network for Congenital Heart Defects plays a substantial part in detecting needs and deficits of the current care for patients with CHD and helps developing strategies for an adequate and efficient care, while guaranteeing a high degree of transparency for those concerned.

Adult↗

PubMed2004

Gene network polymorphism is the raw material of natural selection: the selfish gene network hypothesis.

Population genetics, the mathematical theory of modern evolutionary biology, defines evolution as the alteration of the frequency of distinct gene variants (alleles) differing in fitness over the time. The major problem with this view is that in gene and protein sequences we can find little evidence concerning the molecular basis of phenotypic variance, especially those that would confer adaptive benefit to the bearers. Some novel data, however, suggest that a large amount of genetic variation exists in the regulatory region of genes within populations. In addition, comparison of homologous DNA sequences of various species shows that evolution appears to depend more strongly on gene expression than on the genes themselves. Furthermore, it has been demonstrated in several systems that genes form functional networks, whose products exhibit interrelated expression profiles. Finally, it has been found that regulatory circuits of development behave as evolutionary units. These data demonstrate that our view of evolution calls for a new synthesis. In this article I propose a novel concept, termed the selfish gene network hypothesis, which is based on an overall consideration of the above findings. The major statements of this hypothesis are as follows. (1) Instead of individual genes, gene networks (GNs) are responsible for the determination of traits and behaviors. (2) The primary source of microevolution is the intraspecific polymorphism in GNs and not the allelic variation in either the coding or the regulatory sequences of individual genes. (3) GN polymorphism is generated by the variation in the regulatory regions of the component genes and not by the variance in their coding sequences. (4) Evolution proceeds through continuous restructuring of the composition of GNs rather than fixing of specific alleles or GN variants.

Alleles↗

PubMed2004

First results of Liguria-Trento transplant network project: a model for a macroregional network and real-time registry in Italy.

In Italy, health-care telematic is funded and supported at the level of national government or regional institutions. In 1999, the Italian Ministry of Health started to fund the Liguria-Trento Transplant Network (LTTN) project, a health research project with the aim to build an informative system for donor management and transplantation activity in a macroregional area. At the time of LTTN project proposal, no published Transplant Network Informative System fulfilled Italian rules on telematic management of electronic documentation concerning transplantation activity. Partnership of LTTN project were two Regional Transplant Coordinating Centres, Nord Italia Transplant Interregional Coordinating Centre and the Italian Institute of Health/National Transplant Coordinating Centre. Project Total Quality Management methods were adopted. Technological and case analysis followed ANSI-HL7, CEN-TC251, and Object-Oriented Software Engineering standards. A low-tech prototype powered by a web access relational database is running on a transplant network including web-based clients located in 17 intensive care units, in Nord Italia Transplant Interregional Coordinating Centre, and at the Italian Institute of Health/National Transplant Coordinating Centre. LTTN registry includes pretransplant, surgical, and posttransplant phases regarding liver, kidney, pancreas, and kidney-pancreas transplantation in adult and pediatric recipients. Clinical specifications were prioritized in agreement with the RAND/UCLA appropriateness method. Further implementation will include formal rules for data access and output release, fault tolerance, and a continuous registry evolution plan.

Humans↗

PubMed1999

Multi-sensor integration for on-line tool wear estimation through radial basis function networks and fuzzy neural network.

On-line tool wear estimation plays a very critical role in industry automation for higher productivity and product quality. In addition, appropriate and timely decision for tool change is significantly required in the machining systems. Thus, this paper is dedicated to develop an estimation system through integration of two promising technologies, artificial neural networks (ANN) and fuzzy logic. An on-line estimation system consisting of five components: (1) data collection; (2) feature extraction; (3) pattern recognition; (4) multi-sensor integration; and (5) tool/work distance compensation for tool flank wear, is proposed herein. For each sensor, a radial basis function (RBF) network is employed to recognize the extracted features. Thereafter, the decisions from multiple sensors are integrated through a proposed fuzzy neural network (FNN) model. Such a model is self-organizing and self-adjusting, and is able to learn from the experience. Physical experiments for the metal cutting process are implemented to evaluate the proposed system. The results show that the proposed system can significantly increase the accuracy of the product profile.

Journal Article↗

PubMed1997

Odor, drug and toxin analysis with neuronal networks in vitro: extracellular array recording of network responses.

Neurons, by virtue of intrinsic electrophysiological mechanisms, represent transducers that report the dynamics of cell death, receptor-ligand interactions, alterations in metabolism, and generic membrane perforation processes. In cell culture, mammalian neurons form fault-tolerant, spontaneously active systems with great sensitivity to their chemical environment and generate response profiles that are often concentration- and substance-specific. Changes in action potential patterns are usually detected before morphological changes and cell damage occur, which provides sensitivity and reversibility. Such biological systems can be used to screen rapidly for novel pharmacological substances, toxic agents, and for the detection of certain odorants. Existing simple culture preparations can already be employed effectively for the detection of chemical compounds. So far, three strategies have been investigated in pilot experiments: (1) Substance-dependent major changes in spontaneous native activity patterns. All synaptically active agents (e.g. glutamate, strychnine, N-methyl D-aspartic acid) as well as metabolic poisons generate such changes. (2) Substance-dependent changes in network oscillations via disinhibition. The regularized, oscillatory activity is altered by synaptically and metabolically active substances, ion channel blockers, and toxins. (3) Detection of paroxysmal responses indicating major, pathological membrane currents in large subpopulation of cells. We have explored these three strategies via 64 channel array recordings using spontaneously active murine spinal cord cultures. The glycine receptor blocker strychnine reliably generated increased multichannel bursting at 5-20 nM and regular, coordinated bursting above 5 microM. During biculline-induced network oscillations many compounds alter oscillation frequencies or terminate activity in a substance-specific manner. Finally, the gp120 protein of the AIDS virus (at 1 microgram/ml) produces massive, unique paroxysmal discharges that may last as long as 2 min. These results indicate that cultured neuronal networks are practical systems that can be used for the detection and identification of a great variety of chemical substances. The concept of dynamic fingerprinting to identify specific compounds is discussed.

Animals↗

PubMed1997

Strychnine analysis with neuronal networks in vitro: extracellular array recording of network responses.

Animals↗

PubMed2003

Controlling dimensionality of silver(I) coordination networks with rigid aliphatic amino ligands: from a 2D to a 3D network of unprecedented topology comprising helical channels.

Ligand-directed 2D and 3D Ag(I) coordination networks are self-assembled from the rigid, topologically related tri-amino ligands cis-3,5-diaminopiperidine (cis-dapi) and cis,trans-1,3,5-triaminocyclohexane (trans-tach), yielding two networks of differing dimensionality including a 3D network of unprecedented topology comprising helical channels.

Journal Article↗

PubMed2004

Global network analysis of phenotypic effects: protein networks and toxicity modulation in Saccharomyces cerevisiae.

Using genome-wide information to understand holistically how cells function is a major challenge of the postgenomic era. Recent efforts to understand molecular pathway operation from a global perspective have lacked experimental data on phenotypic context, so insights concerning biologically relevant network characteristics of key genes or proteins have remained largely speculative. Here, we present a global network investigation of the genotype/phenotype data set we developed for the recovery of the yeast Saccharomyces cerevisiae from exposure to DNA-damaging agents, enabling explicit study of how protein-protein interaction network characteristics may be associated with phenotypic functional effects. We show that toxicity-modulating proteins have similar topological properties as essential proteins, suggesting that cells initiate highly coordinated responses to damage similar to those needed for vital cellular functions. We also identify toxicologically important protein complexes, pathways, and modules. These results have potential implications for understanding toxicity-modulating processes relevant to a number of human diseases, including cancer and aging.

Cluster Analysis↗

PubMed2005

Entangled networks, synchronization, and optimal network topology.

A new family of graphs, entangled networks, with optimal properties in many respects, is introduced. By definition, their topology is such that it optimizes synchronizability for many dynamical processes. These networks are shown to have an extremely homogeneous structure: degree, node distance, betweenness, and loop distributions are all very narrow. Also, they are characterized by a very interwoven (entangled) structure with short average distances, large loops, and no well-defined community structure. This family of nets exhibits an excellent performance with respect to other flow properties such as robustness against errors and attacks, minimal first-passage time of random walks, efficient communication, etc. These remarkable features convert entangled networks in a useful concept, optimal or almost optimal in many senses, and with plenty of potential applications in computer science or neuroscience.

Animals↗

PubMed2006

Direction of the Organ Procurement and Transplantation Network and United Network for Organ Sharing regarding the oversight of live donor transplantation and solicitation for organs.

The Organ Procurement and Transplantation Network (OPTN) operated by United Network for Organ Sharing (UNOS) has taken recent steps to address public solicitation for organ donors and its oversight of live donor transplantation. This report provides the direction of the OPTN regarding deceased donor solicitation. The OPTN has authority under federal law to equitably allocate deceased donor organs within a single national network based upon medical criteria, not upon one's social or economic ability to utilize resources not available to all on the waiting list. The OPTN makes a distinction between solicitations for a live donor organ versus solicitations for directed donation of deceased organs. As to live donor solicitation, the OPTN cannot regulate or restrict ways relationships are developed in our society, nor does it seek to do so. OPTN members have a responsibility of helping protect potential recipients from hazards that can arise from public appeals for live donor organs. Oversight and support of the OPTN for live donor transplantation is now detailed by improving the reporting of live donor follow-up, by providing a mechanism for facilitating anonymous live kidney donation, and by providing information for potential live kidney donors via the UNOS Transplant Living website.

Directed Tissue Donation↗

PubMed2002

Quantification of gastric mill network effects on a movement related parameter of pyloric network output in the lobster.

It has long been known that gastric mill network activity (cycle period 5-10 s) alters pyloric network output (cycle period approximately 1 s), but these effects have not been quantified. Many pyloric muscles extract gastric mill timed variations in pyloric motor neuron firing, and consequently produce gastric mill timed movements even though no gastric mill neurons innervate them. Determining pyloric behavior therefore requires detailed description of gastric mill effects on pyloric neural output. Pyloric muscle activity correlates well with motor neuron overall spike frequency (OSF, burst spike number divided by cycle period). We quantified OSF variation of all pyloric neurons as a function of time into the gastric mill cycle [as measured from the beginning of Gastric Mill (GM) neuron bursts] in the lobster, Panulirus interruptus. No repeating pattern within individual gastric mill cycles of Lateral Pyloric (LP) and Ventricular Dilator (VD) neuron OSF was visually apparent. Averaged data showed that VD and LP neuron OSF decreased (approximately 0.5 and 1.5 Hz, respectively) at the beginning of each gastric mill cycle. Visually apparent patterns of OSF waxing and waning within each gastric mill cycle were present for the Inferior Cardiac (IC), Pyloric Dilator (PD), and Pyloric (PY) neurons. However, when averaged as a function of phase or delay in the gastric mill cycle, the average changes were smaller than those in individual gastric mill cycles because when the OSF variations occurred varied considerably in different gastric mill cycles. We therefore used a "pattern-based" analysis in which an identifying characteristic of each neuron's repeating OSF variation pattern was defined as pattern pyloric cycle zero. The pyloric cycles in each repetition of the OSF variation pattern were numbered relative to the zero cycle, and averaged to create an average OSF variation profile. The zero cycle delays relative to GM neuron burst beginning were then averaged to determine when in the gastric mill cycle the profile occurred. This technique preserved the full extent of pyloric neuron OSF changes. Maximum PY neuron OSF occurred within the GM neuron burst, whereas maximum IC and PD neuron OSF occurred during the GM neuron interburst interval. Despite these changes, pyloric cycling did not phase lock with gastric mill activity, nor were an integer number of pyloric cycles present in each gastric mill cycle. In addition to providing data necessary to predict pyloric movement, this work shows how pattern-based analysis can successfully quantify interactions between nonphase-locked networks.

Action Potentials↗