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Results for “network physiology”

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At least 631 records · Page 35Linked to original sources
PubMed1988

Effect of water-soluble iodinated contrast media on pressure-flow relationship of red cell suspension.

The effect of radiological contrast media on blood flow through a vascular network was investigated, taking physical and physiological conditions such as osmolality into account. The perfusion of the bullfrog's hind limbs was performed, with a slight modification of the vertical tube method. The effect of contrast media on red cell deformability was studied by perfusion with erythrocyte suspensions in glutaraldehyde-fixed hind limbs. The echinocytic shape change induced by metrizamide and hypertonic iothalamate solutions caused a marked increase in resistance to flow. When the perfusion with erythrocyte suspension was performed using intact hind limbs, the pressure-flow relationship was influenced by contrast media effects on both red cell deformability and the vascular bed. Ioxaglate had less rheologic effect on the pressure-flow relationship than metrizamide or iothalamate. It could be concluded that contrast media should be isotonic, of low viscosity and chemotoxicity, and that ioxaglate was preferable to metrizamide and iothalamate at equal iodine content.

Animals↗
PubMed2003

Self-organization and complexity: a new age for theory, computation and experiment.

I first describe the notion of self-organization as a property of far-from-equilibrium nonlinear dissipative dynamical systems. Rather than describing such complex systems at a purely phenomenological level, however, I focus attention on the emergent nature of this complexity, by analysing a few examples of physical and physicochemical systems with simple underlying microscopic dynamics yet complex, self-organizing macroscopic properties. These include several mesoscopic models of fluid dynamics as well as a modern approach to nucleation and growth phenomena. Finally, I discuss how the advent of computational grids is set to provide a major boost to the study of such complex, self-organizing systems.

Adaptation, Physiological↗
PubMed2000

Sensitivity and versatility of an adaptive system for controlling cyclic movements using functional neuromuscular stimulation.

This study evaluated an adaptive control system (the PG/PS control system [2]) that had been designed for generating cyclic movements using functional neuromuscular stimulation (FNS). Extensive simulations using computer-based models indicated that a broad range of control system parameter values performed well across a diverse population of model systems. The fact that manual tuning is not required for each individual makes this control system particularly attractive for implementation in FNS systems outside of research laboratories.

Algorithms↗
PubMed2001

Linear prediction coding analysis and self-organizing feature map as tools to classify stress calls of domestic pigs (Sus scrofa).

It is assumed that calls may give information about the inner (emotional) state of an animal. Hence, in the last years sound analysis has become an increasingly important tool for the interpretation of the behavior, the health condition, and the well-being of animals. A procedure was developed that allows the characterization, classification, and visualization of the cluster structures of stress calls of domestic pigs (Sus scrofa). Based on the acoustic model of the sound production the extraction of features from calls was performed with linear prediction coding (LPC). A vector-based self-organizing neuronal network was trained with the determined LPC coefficients, resulting in a feature map. The cluster structure of the calls was then visualized with a unified matrix and the neurons were labeled for their input origin. The basic applicability of the procedure was tested by using two examples which were of special interest for a possible evaluation of the normal farming practice. The procedure worked well both in discriminating individual piglets by their scream characteristics and in classifying pig stress calls vs other calls and noise occurring under normal farming conditions.

Acoustics↗
PubMed2007

Wireless connectivity for health and sports monitoring: a review.

This is a review of health and sports monitoring research that uses or could benefit from wireless connectivity. New, enabling wireless connectivity standards are evaluated for their suitability, and an assessment of current exploitation of these technologies is summarised. An example of the application is given, highlighting the capabilities of a network of wireless sensors. Issues of timing and power consumption in a battery-powered system are addressed to highlight the benefits networking can provide, and a suggestion of how monitoring different biometric signals might allow one to gain additional information about an athlete or patient is made.

Computer Communication Networks↗
PubMed2003

Metabolomics in systems biology.

The primary aim of "omic" technologies is the nontargeted identification of all gene products (transcripts, proteins, and metabolites) present in a specific biological sample. By their nature, these technologies reveal unexpected properties of biological systems. A second and more challenging aspect of omic technologies is the refined analysis of quantitative dynamics in biological systems. For metabolomics, gas and liquid chromatography coupled to mass spectrometry are well suited for coping with high sample numbers in reliable measurement times with respect to both technical accuracy and the identification and quantitation of small-molecular-weight metabolites. This potential is a prerequisite for the analysis of dynamic systems. Thus, metabolomics is a key technology for systems biology. The aim of this review is to (a) provide an in-depth overview about metabolomic technology, (b) explore how metabolomic networks can be connected to the underlying reaction pathway structure, and (c) discuss the need to investigate integrative biochemical networks.

Models, Biological↗
PubMed2003

Inference and computation with population codes.

In the vertebrate nervous system, sensory stimuli are typically encoded through the concerted activity of large populations of neurons. Classically, these patterns of activity have been treated as encoding the value of the stimulus (e.g., the orientation of a contour), and computation has been formalized in terms of function approximation. More recently, there have been several suggestions that neural computation is akin to a Bayesian inference process, with population activity patterns representing uncertainty about stimuli in the form of probability distributions (e.g., the probability density function over the orientation of a contour). This paper reviews both approaches, with a particular emphasis on the latter, which we see as a very promising framework for future modeling and experimental work.

Animals↗
PubMed2003

Cellular and network mechanisms of slow oscillatory activity (<1 Hz) and wave propagations in a cortical network model.

Slow oscillatory activity (<1 Hz) is observed in vivo in the cortex during slow-wave sleep or under anesthesia and in vitro when the bath solution is chosen to more closely mimic cerebrospinal fluid. Here we present a biophysical network model for the slow oscillations observed in vitro that reproduces the single neuron behaviors and collective network firing patterns in control as well as under pharmacological manipulations. The membrane potential of a neuron oscillates slowly (at <1 Hz) between a down state and an up state; the up state is maintained by strong recurrent excitation balanced by inhibition, and the transition to the down state is due to a slow adaptation current (Na(+)-dependent K(+) current). Consistent with in vivo data, the input resistance of a model neuron, on average, is the largest at the end of the down state and the smallest during the initial phase of the up state. An activity wave is initiated by spontaneous spike discharges in a minority of neurons, and propagates across the network at a speed of 3-8 mm/s in control and 20-50 mm/s with inhibition block. Our work suggests that long-range excitatory patchy connections contribute significantly to this wave propagation. Finally, we show with this model that various known physiological effects of neuromodulation can switch the network to tonic firing, thus simulating a transition to the waking state.

Algorithms↗
PubMed2003

Neuromuscular modulation in Aplysia. I. Dynamic model.

Many physiological systems are regulated by complex networks of modulatory actions. Here we use mathematical modeling and complementary experiments to study the dynamic behavior of such a network in the accessory radula closer (ARC) neuromuscular system of Aplysia. The ARC muscle participates in several types of rhythmic consummatory feeding behavior. The muscle's motor neurons release acetylcholine to produce basal contractions, but also modulatory peptide cotransmitters that, through multiple cellular effects, shape the contractions to meet behavioral demands. We construct a dynamic model of the modulatory network and examine its operation as the motor neurons fire in realistic patterns that change gradually over an hour-long meal and abruptly with switches between the different feeding behaviors. The modulatory effects have very disparate dynamical time scales. Some react to the motor neuron firing only over many cycles of the behavior, but one key effect is fast enough to respond to each individual cycle. Switches between the behaviors are therefore followed by rapid relaxations along some modulatory dimensions but not others. The trajectory of the modulatory state is a transient throughout the meal, ranging widely over regions of the modulatory space not accessible in the steady state. There is a pronounced history-dependency: the modulatory state associated with a cycle of a particular behavior depends on when that cycle occurs and what behaviors preceded it. On average, nevertheless, each behavior is associated with a different modulatory state. In the following companion study, we add a model of the neuromuscular transform to reconstruct and evaluate the actual modulated contraction shapes.

Animals↗
PubMed1997

[Promotion of orodental health in adolescents in Africa].

Bad dental hygiene in adults is usually the result of bad care during childhood. Within the framework of Health for All, WHO and the International Dental Federation defined global objectives for dental health which allow for monitoring progress in different countries. The most common dental problems, such as dental cavities, can be prevented by simple and inexpensive methods. Dental health is based on dental hygiene, nutrition, fluoride intake and dental service utilisation. Dental health promotion aims to create an environment favourable to the adoption of these healthy behaviours. The principle recommended dental health measures are through fluoridation of water, salt, and milk, a low consumption of sweets, and modification of the amount of sugar in the diet; implementation of monitored dental hygiene activities in schools; the organisation of regular dental services in schools/workplaces; and adopting legislative texts or laws requiring certain measures of prevention. In the past several years, certain African countries have set up national dental health programmes (there were 12 in 1993), However, the implementation of dental health promotion generally doesn't result from a national initiative, but from a regional or local scale. This is largely due to the lack of integration of dental health in activities of education and health promotion in general. Programmes planned at a national level and then implemented at a local level on a multisectoral base have had more success. This article presents examples of dental health promotion activities in several African countries, mainly focusing on programmes aimed at 12-13 year olds in primary school. Programmes from Morocco, Kenya, Madagascar, Côte d'Ivoire, Benin, and Tanzania are briefly presented and show that in Africa, dental health promotion has mostly consisted of the implementation of health education actions and that there are no consistent policies, unlike in other developing countries, for fluoridation of water, salt, and milk. In terms of dental health promotion, WHO recommends the promotion of traditional methods of dental hygiene (such as plants or sticks for cleaning), especially among adolescents living in rural and low income communities. In turn, the identification and promotion of the positive aspects of hygiene and traditional care will allow for the implementation of more culturally acceptable approaches.

Adolescent↗
PubMed2005

Barriers and pathways to diffusion of methamphetamine use among African Americans in the rural South: preliminary ethnographic findings.

There are no studies of African Americans methamphetamine use in the South where it is widespread among whites. We describe factors that inhibit or facilitate the diffusion of methamphetamine use among African Americans based on qualitative interviews with 86 drug users in rural Arkansas and Kentucky. Results suggest low prevalence of methamphetamine use among African Americans, and interviewees cited several barriers to its diffusion which were linked to the drug's ingredients, psychoactive and physiological effects, difficulty in accessing distribution networks, and established African-American preference for cocaine. Fourteen African Americans reported methamphetamine use and discussed pathways to it. Possible increases in African- American methamphetamine use merits further investigation.

Adult↗
PubMed1996

Nonlinearities within the cat LGN cell receptive fields in simulated network with recurrent inhibition.

We investigated the receptive fields of principal cells from the cat's lateral geniculate nucleus cells. About 20% of the X type neurones showed clear nonlinearities of summation when stimulated by two simultaneously onset, small bars of light. The possible source of this nonlinearity was studied on a specially designed model of a one-layer neuronal network with inhibitory, recurrent interactions, intended to mimic the inhibitory influence exerted on geniculate relay cells by perigeniculate interneurones. The model, when activated from periphery by two stimuli-like input patterns, produced at the output side the nonsymmetrical profiles of the receptive fields sensitivity, similar to those obtained in real experiments. This nonlinear output appeared when some of the relay cells were inhibited below their firing level threshold and this effect was spread through the network by lateral inhibitory connections. It is concluded that physiologically observed nonlinearities of the order of single receptive field mechanisms can be predicted by a simple recurrent network.

Animals↗
PubMed1998

Community medical care monitoring system for chronic patient.

The chronic disease usually can not be cured well but controlling by the daily care activity, regular diagnosis and dosage under the physician's instructions. In this research, we propose a community medical care monitoring model for monitoring and managing the chronic patients of community through the WWW (World Wide Web) service network and/or telephone voice service network. It can collect more patients' physiological data measured at home or community health agent. Therefore, the chronic disease patients will be getting better cure from his doctor's diagnosis due to the patient's effort.

Chronic Disease↗
PubMed1999

Telemedicine technology and applications for home hemodialysis.

Home hemodialysis (HD) for the treatment of patients with end-stage renal disease (ESRD) was first put into practice about 30 years ago. In this paper we describe the application of telematics monitoring services (TMS) for supporting patients who need home or satellite HD (SHD). For the clinical trials two modified HD machines were located in the renal unit and a central control station (UNIX workstation with multimedia PC-terminal) was located in another room of the hospital. Bi-directional communication between modified HD machines and central control station was managed via ISDN (Integrated Services Digital Network) links. Using these HD-machines 150 HD sessions were performed in nine patients over a period of five months. This system enabled on-line remote supervision of the HD machine-related functions (air in the blood, leak of blood, low conductivity etc.) and the clinical condition of patients through measurement of blood pressure (BP), pulse rate, PO2 (pulse oxymetry) and electrocardiogram (ECG) from the central control station (CCS). The user checked the type of alarm/warning, its appearance on HD machines and multimedia terminal units (MTU), the action of the protective system and the appearance of consultative messages from CCS on the remote terminal unit RTU. According to the data collected, the disturbances of HD machine function were visible and audible in the CCS and the user messages were always observed on the RTU. No unusual dialysis-associated complications were observed, all data and alarms/warnings were transmitted correctly and patients had adequate HD treatment.

Female↗