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PubMed1984

Disappearance of the cartilage interlacunar network during histological dehydration.

The interlacunar network connects adjacent chondrocytes in rapidly growing cartilage and with anionic dyes stains more intensely than the surrounding matrix. The network is seen in fresh-frozen sections and sections treated with a variety of fixatives, dehydration agents and embedding media. The network is not seen after using such common dehydrating fluids as ethanol and acetone. Polyanionic glycosaminoglycans (GAG) are abundant in the cartilage matrix and it has been suggested that the network is an artifact caused by a rearrangement of the matrix GAG during histological processing. Extraction of GAG from neonatal rat cartilage with guanidine hydrochloride removes stainable extracellular matrix but not the interlacunar network. However, after extraction of GAG and immersion of the cartilage in either 50% or 100% aqueous ethanol or acetone, the network was no longer visible. The network apparently is not an artifact formed by soluble matrix GAG, but a real structure which is extracted, collapsed or otherwise destroyed during dehydration in ethanol or acetone.

Animals↗
PubMed2005

Quebec mental health services networks: models and implementation.

PURPOSE: In the transformation of health care systems, the introduction of integrated service networks is considered to be one of the main solutions for enhancing efficiency. In the last few years, a wealth of literature has emerged on the topic of services integration. However, the question of how integrated service networks should be modelled to suit different implementation contexts has barely been touched. To fill that gap, this article presents four models for the organization of mental health integrated networks. DATA SOURCES: The proposed models are drawn from three recently published studies on mental health integrated services in the province of Quebec (Canada) with the author as principal investigator. DESCRIPTION: Following an explanation of the concept of integrated service network and a description of the Quebec context for mental health networks, the models, applicable in all settings: rural, urban or semi-urban, and metropolitan, and summarized in four figures, are presented. DISCUSSION AND CONCLUSION: To apply the models successfully, the necessity of rallying all the actors of a system, from the strategic, tactical and operational levels, according to the type of integration involved: functional/administrative, clinical and physician-system is highlighted. The importance of formalizing activities among organizations and actors in a network and reinforcing the governing mechanisms at the local level is also underlined. Finally, a number of integration strategies and key conditions of success to operationalize integrated service networks are suggested.

Journal Article↗
PubMed2001

Three-dimensional morphology of c-Kit-positive cellular network and nitrergic innervation in the human gut.

CONTEXT: -c-Kit-positive interstitial cells of Cajal (ICC) appear to play a key role in the normal motility function and development of intestine. Nitric oxide is considered to be the most important messenger of inhibitory nonadrenergic, noncholinergic nerves in the enteric nervous system. OBJECTIVES: The aims of this study were to examine the distribution of nitrergic innervation and ICCs in normal human bowel and to demonstrate interconnections between ICCs and nitrergic nerves and smooth muscle fibers using histochemical and immunohistochemical double-staining methods with a whole-mount preparation technique and confocal laser scanning microscopy. METHODS: Full-thickness small and large bowel specimens were obtained at autopsy from 18 children who died of nongastrointestinal diseases. A whole-mount preparation was performed for all specimens, and double staining was carried out with nicotinamide adenine dinucleotide phosphate (reduced form, NADPH)-diaphorase and c-Kit immunohistochemistry. Double immunofluorohistochemistry with neuronal nitric oxide synthase and c-Kit using confocal laser scanning microscopy was also performed in all specimens. RESULTS: The whole-mount preparation facilitated 3-dimensional visualization of the meshlike network of NADPH-diaphorase-positive nerve fibers in the myenteric plexus surrounded by a reticular network of c-Kit-positive ICCs. The dense c-Kit-positive cellular network located between longitudinal and circular muscle layers and at the innermost part of circular muscle layer intermingled with the myenteric plexus. Short, fine processes of ICCs made connections with the muscle fibers and c-Kit-positive cells. CONCLUSIONS: The development of double-NADPH-diaphorase histochemistry and c-Kit immunohistochemistry staining technique in a whole-mount preparation provides an easy and useful method for investigating the association between c-Kit-positive cellular network and nitrergic neuronal network in the human bowel wall. The characteristic profiles of the c-Kit-positive cellular network and nitrergic neuronal network and their relationship with the smooth muscle fibers provide a morphologic basis for investigating intestinal motility disorders.

Fluorescent Antibody Technique↗
PubMed1999

Early effects of ionizing radiation on the microvascular networks in normal tissue.

Microvascular networks, which control the delivery of oxygen and nutrients and the removal of metabolic waste, are the most sensitive part of the vascular system to ionizing radiation. Structural and functional changes in microvascular networks were studied in locally irradiated (single 10-Gy dose) hamster cremaster muscles observed 3, 7 and 30 days post-irradiation. Networks were selected in reference to a well-defined location in the tissue to reduce heterogeneity due to spatial variations. Intravital microscopy was used to measure structural and functional parameters in vivo. A factorial design was used to examine the effects of radiation status, time postirradiation, and network vessel type on the structure and function of microvascular networks. While the diameter of microvessels in control animals increased significantly with age, vessel diameter in irradiated vessels decreased significantly with age. Red blood cell velocity in irradiated networks at 3 and 30 days postirradiation was significantly lower than in control networks. There was a significant decrease in capillary surface area and a significant increase in vessel hematocrit in irradiated animals. Blood flow in irradiated vessels was significantly lower than in control vessels. Changes in functional parameters were evident at 3 days postirradiation while changes in structural parameters occurred later. All vessel types were not damaged equally by radiation at every time examined.

Animals↗
PubMed1999

[The use of computers and networking in the neurosurgical field].

Due to the improvements in computer and network technology, we are able to use medical information easily and safely on the network in medical institutions. In our department, we constructed and used an original Intranet with light fibers. The network links the outpatient room, ward, operation room, staff room and the examination room. Moreover, many computers and medical instruments are connected to the Intranet. Since our original Intranet has no connection with the outside network, we are able to access the patient's medical information safely. Using access management of identity and a password on the server, the client can present the medical information with sound and movie upon request of the patients and their families, medical students, nurses and doctors. Doctors can also search and input the patient's most recent medical information on a network database of every client. By linking the examination machine and operation aided instrument to the Intranet, we were able to forward the patient's medical information to the operation aided instrument easily and quickly. Furthermore, we will be able to perform tele-medicine and tele-operation in the near future: that is, the medical staff can guide the neurosurgical operation outside of the operation room with a microscope and computer view using picture mutual communication devices. By strict access to the management of our Intranet, we are able to use the medical information effectively for patient's treatment, operation, education and study on the network with no connection to the outside network.

Databases, Factual↗
PubMed2000

Gap junctions linking the dendritic network of GABAergic interneurons in the hippocampus.

The network of GABAergic interneurons connected by chemical synapses is a candidate for the generator of synchronized oscillations in the hippocampus. We present evidence that parvalbumin (PV)-containing GABAergic neurons in the rat hippocampal CA1 region, known to form a network by mutual synaptic contacts, also form another network connected by dendrodendritic gap junctions. Distal dendrites of PV neurons run parallel to the alveus (hippocampal white matter) and establish multiple contacts with one another at the border between the stratum oriens and the alveus. In electron microscopic serial section analysis, gap junctions could be identified clearly at 24% of these contact sites. A dendrodendritic chemical synapse and a mixed synapse also were found between PV-immunoreactive dendrites. Three-dimensional reconstruction of the dendritic arborization revealed that both PV neurons of the well known vertical type (presumptive basket cells and axoaxonic cells) and those of another horizontal type constitute the dendritic network at the light microscopic level. The extent of dendritic fields of single PV neurons in the lateral direction was 538 +/- 201 micrometer (n = 5) in the vertical type and 838 +/- 159 micrometer (n = 6) in the horizontal type. Our previous and present observations indicate that PV-containing GABAergic neurons in the hippocampus form the dual networks connected by chemical and electrical synapses located at axosomatic and dendrodendritic contact sites, respectively. Gap junctions linking the dendritic network may mediate coherent synaptic inputs to distant interneurons and thereby facilitate the synchronization of oscillatory activities generated in the interneuron network.

Animals↗
PubMed1999

[Pediatric research in an office-setting network--a new dimension in pediatric research in Israel].

Pediatric care in the community is gradually replacing traditional care in hospitals. Despite that, research activity in the community setting is minimal due to objective difficulties. These are mainly constraints of time, office work and lack of research-supporting logistics. In the past decade, throughout the world, primary physicians interested in research have grouped together and formed research networks. The aim of such networks is to support and promote research in the community. An Israel Pediatric Research in Office-Setting network (IPROS) was established 2 years ago by the Israel Ambulatory Pediatric Association (IAPA). Today, there are over 140 pediatricians listed in IPROS, representing the heterogeneous composition of pediatricians in Israel. The network's policy is defined by a joint steering committee. The committee is composed of IAPA representatives, senior network members and Schneider Hospital senior investigators. The research subjects are diverse, and represent common practical issues. Effective intra-net communication is vital to the existence of the network, and is accomplished by 3 modalities: 1) semiannual updates by mail, 2) e-mail, using an electronic mailing list to facilitate connection between members, 3) semi-annual meetings. Research budgets are derived from public sources like the Ministry of Health and IAPA, and private sources such as pharmaceutical companies. The administration of the network is supported by Schneider Children's Medical Center, and financed by IAPA.

Ambulatory Care↗
PubMed2000

Modulation in firing pattern and oscillation in nerve cells of Lymnaea during network reconstruction.

The modulation and reconstruction of the cardio-respiratory neural circuit of Lymnaea stagnalis L. was compared to that of Helix ponatia L. where the input variation and signal molecules were found to have primary importance in network reorganization. From the cardio-respiratory circuit only neurons connected by afferent or efferent pathways to the peripheral chemosensory organ, the osphradium, were used. It was shown that, the general principles of the network reorganization is similar in the two species. The firing pattern of the neurons altered in Lymnaea depending on the input activation or presence of signal molecules in the vicinity of the neurons. The responses of the neurons to the same sensory information, originating from osphradium varied depending on their firing patterns. On central neurones the generation of phasic pattern and/or oscillation was an indicator of network disintegration leading to insensibility to the osphradial sensory inputs. Co-application of signal molecules (5HT, DA, GABA with opioid peptides) to the neurons caused a phasic firing pattern and/or oscillation leading to disintegration of one network and activation of another one. The effect of mu-opioid peptides on GABA-induced and voltage activated ion currents were shown to be the cellular target in reconstruction of neural networks in Lymnaea. The neural network reconstruction in vertebrate brain evoked by signal molecules can be compared to that observed in the identified network of Lymnaea stagnalis making this latter a useful model in further studies, too.

Animals↗
PubMed2000

Family practice research networks. Experiences from 3 countries.

Access to data about the clinical problems, patients, and processes that characterise family practice is essential for the development of this specialty. Practice-based research networks (PBRNs) play an increasing role in obtaining these data. We compared 3 PBRNs: one in Wisconsin in the United States, one in Wessex in the United Kingdom, and one in Nijmegen in the Netherlands. We organized our data into 4 key areas for review: the mission of the network, its contribution to the evidence base of family medicine, the management of the network, and the financing of the network infrastructure. Extending the evidence base of family practice is the overriding objective of these networks, and their main focus is on common morbidities. They provide access to unselected patient populations, but there are differences in their size. There are aspects of PBRNs that are common in countries with different health care systems, despite the fact that local circumstances--the research mission or the characteristics of the health care system under which they operate--determine their form and structure. Networks develop over time and their focus and activities may evolve. Financial support for these networks continues to be a problem.

Family Practice↗
PubMed2000

Comparison of high dose buprenorphine treatments of opiate dependent outpatients in four healthcare networks.

AIMS: The aim of this study was to compare the various clinical practices in four health care networks and to access how the variations in treatment effected the outcome in opiate-dependent patients. METHODS: A retrospective study was carried out with 71 participating general practitioners. These were chosen from a group of 354 practitioners from four health care networks. Each practitioner could enroll up to 5 patients who were currently undergoing treatment with high-dose buprenorphine(HDB). The patients treatment had to have been initiated between the 1(st) of February 1996 and the 31(st) of October 1996, and excluded any patients who had lapsed on their treatment during the first month. Patients were selected until a total of 75 cases were enrolled from each network. Data were then collected retrospectively between June and December 1997. Information collected concerned the initial stage of treatment, the stabilizing stage or level of treatment and followed up data on the most recent prescriptions. RESULTS: The final patient maintenance totals were high for all four care networks (82.7 to 96% of patients were still being followed by their doctor at the final evaluation). A positive outcome as indicated by reduction of risk and decreased social vulnerability was also observed in all networks. Additionally, in each network there was a clear correlation between prescription practices and patient behavior. For example, the prescription of HDB at a daily dose of less than 6.2mg was associated with a higher rate of benzodiazepine use; and prescription of several daily doses of HDB was associated with a higher percentage of injecting patients. CONCLUSION: This retrospective study provides evidence that general practitioner care of drug-dependent patients as outpatients, within a health care network helps to stabilize patient visits, allows treatment of associated comorbidities and favors social rehabilitation. The prescription of HDB as a single daily dose, individually adapted for each patient, optimizes the outcome and reduces misuse.

Adult↗
PubMed2000

Self-organized synchronous oscillations in a network of excitable cells coupled by gap junctions.

Recent evidence suggests that electrical coupling plays a role in generating oscillatory behaviour in networks of neurons; however, the underlying mechanisms have not been identified. Using a cellular automata model proposed by Traub et al (Traub R D, Schmitz D, Jefferys J G and Draguhn A 1999 High-frequency population oscillations are predicted to occur in hippocampal pyramidal neural networks interconnected by axo-axonal gap junctions Neuroscience 92 407-26), we describe a novel mechanism for self-organized oscillations in networks that have strong, sparse random electrical coupling via gap junctions. The network activity is generated by random spontaneous activity that is moulded into regular population oscillations by the propagation of activity through the network. We explain how this activity gives rise to particular dependences of mean oscillation frequency on network connectivity parameters and on the rate of spontaneous activity, and we derive analytical expressions to approximate the mean frequency and variance of the oscillations. In doing so, we provide insight into possible mechanisms for frequency control and modulation in networks of neurons.

Action Potentials↗
PubMed2000

Quality of social network for pregnant women in Japan with focus on parity and family structure.

The purpose of this study was to identify 1) the quality of human network of a pregnant woman, and 2) characteristics of a high-risk pregnant woman for motherhood due to the shortage of social support. We reviewed social network system using a questionnaire: size; nature of relationship with a pregnant woman; duration of relationship with her; frequency of contact with her; and distance from her residence. We also categorized the subjects according to two typical conditions: parity (primigravida or multigravida) and family structure (nuclear or extended). The author interviewed 125 subjects in their final trimester, living in Narashino City near Tokyo to answer the questionnaires. 117 pregnant women agreed and participated in the study. It was found that our subjects had the social network consisted of the mean size of 9.0 supportive members (SD = 1.9), which was similar to that (8.5) reported in the USA by Cronenwett. Our subject perceived her husband and mother most important as supportive members. 10 to 20% of our subjects perceived husbands' mothers, brothers, and even their friends as non-supportive members. Roughly 40 to 60% of our subjects did not list husbands' fathers, brothers and fathers as network members. We found that pregnant women in Japan, especially primigravidas and pregnant women belonging to nuclear family, had poor quality of social support network. Pregnant women with poor quality of social network were considered as high risk for emotional and behavioral problems both to mother and child. Therefore, midwives should be able to predict the risk or mental stress in childcare due to shortage of social support. This will avoid child abuse through the establishment of necessary human network for isolated mothers.

Adult↗
PubMed2001

The role of activity-dependent network depression in the expression and self-regulation of spontaneous activity in the developing spinal cord.

Spontaneous episodic activity occurs throughout the developing nervous system because immature circuits are hyperexcitable. It is not fully understood how the temporal pattern of this activity is regulated. Here, we study the role of activity-dependent depression of network excitability in the generation and regulation of spontaneous activity in the embryonic chick spinal cord. We demonstrate that the duration of an episode of activity depends on the network excitability at the beginning of the episode. We found a positive correlation between episode duration and the preceding inter-episode interval, but not with the following interval, suggesting that episode onset is stochastic whereas episode termination occurs deterministically, when network excitability falls to a fixed level. This is true over a wide range of developmental stages and under blockade of glutamatergic or GABAergic/glycinergic synapses. We also demonstrate that during glutamatergic blockade the remaining part of the network becomes more excitable, compensating for the loss of glutamatergic synapses and allowing spontaneous activity to recover. This compensatory increase in the excitability of the remaining network reflects the progressive increase in synaptic efficacy that occurs in the absence of activity. Therefore, the mechanism responsible for the episodic nature of the activity automatically renders this activity robust to network disruptions. The results are presented using the framework of our computational model of spontaneous activity in the developing cord. Specifically, we show how they follow logically from a bistable network with a slow activity-dependent depression switching periodically between the active and inactive states.

Animals↗
PubMed2001

Widowhood and illness: a comparison of social network characteristics in France, Germany, Japan, and the United States.

This study examined social network characteristics of adults aged 70 to 90 years in relation to widowhood and illness in France, Germany, Japan, and the United States. Participants were drawn from representative samples from each of the 4 countries (total N = 1,331). Resource deficit profiles based on whether respondents were widowed, ill, both, or neither were directly related to social network characteristics for German and Japanese adults, were differentially related by gender and age for French adults, and were not related to social networks of Americans. Country, gender, and age differences in total network size, proportion of close network members, and frequency of contact with network members are reported. Similarities and differences found in the associations between normative late-life deficits and social network characteristics in the 4 countries point to the importance of investigating sociocultural factors that mediate the impact of resource loss and afford life quality in very old age.

Aged↗
PubMed2002

The restricted influence of sparseness of coding on the capacity of familiarity discrimination networks.

Much evidence indicates that the perirhinal cortex is involved in the familiarity discrimination aspect of recognition memory. It has been previously shown under selective conditions that neural networks performing familiarity discrimination can achieve very high storage capacity, being able to deal with many times more stimuli than associative memory networks can in associative recall. The capacity of associative memories for recall has been shown to be highly dependent on the sparseness of coding. However, previous work on the networks of Bogacz et al, Norman and O'Reilly and Sohal and Hasselmo that model familiarity discrimination in the perirhinal cortex has not investigated the effects of the sparseness of encoding on capacity. This paper explores how sparseness of coding influences the capacity of each of these published models and establishes that sparse coding influences the capacity of the different models in different ways. The capacity of the Bogacz et al model can be made independent of the sparseness of coding. Capacity increases as coding becomes sparser for a simplified version of the neocortical part of the Norman and O'Reilly model, whereas capacity decreases as coding becomes sparser for a simplified version of the Sohal and Hasselmo model. Thus in general, and in contrast to associative memory networks, sparse encoding results in little or no advantage for the capacity of familiarity discrimination networks. Hence it may be less important for coding to be sparse in the perirhinal cortex than it is in the hippocampus. Additionally, it is established that the capacities of the networks are strongly dependent on the precise form of the learning rules (synaptic plasticity) used in the network. This finding indicates that the precise characteristics of synaptic plastic changes in the real brain are likely to have major influences on storage capacity.

Animals↗
PubMedDate not supplied

A hydrologic network supporting spatially referenced regression modeling in the Chesapeake Bay Watershed.

The U.S. Geological Survey has developed a methodology for statistically relating nutrient sources and land-surface characteristics to nutrient loads of streams. The methodology is referred to as SPAtially Referenced Regressions On Watershed attributes (SPARROW), and relates measured stream nutrient loads to nutrient sources using nonlinear statistical regression models. A spatially detailed digital hydrologic network of stream reaches, stream-reach characteristics such as mean streamflow, water velocity, reach length, and travel time, and their associated watersheds supports the regression models. This network serves as the primary framework for spatially referencing potential nutrient source information such as atmospheric deposition, septic systems, point-sources, land use, land cover, and agricultural sources and land-surface characteristics such as land use, land cover, average-annual precipitation and temperature, slope, and soil permeability. In the Chesapeake Bay watershed that covers parts of Delaware, Maryland, Pennsylvania, New York, Virginia, West Virginia, and Washington D.C., SPARROW was used to generate models estimating loads of total nitrogen and total phosphorus representing 1987 and 1992 land-surface conditions. The 1987 models used a hydrologic network derived from an enhanced version of the U.S. Environmental Protection Agency's digital River Reach File, and course resolution Digital Elevation Models (DEMs). A new hydrologic network was created to support the 1992 models by generating stream reaches representing surface-water pathways defined by flow direction and flow accumulation algorithms from higher resolution DEMs. On a reach-by-reach basis, stream reach characteristics essential to the modeling were transferred to the newly generated pathways or reaches from the enhanced River Reach File used to support the 1987 models. To complete the new network, watersheds for each reach were generated using the direction of surface-water flow derived from the DEMs. This network improves upon existing digital stream data by increasing the level of spatial detail and providing consistency between the reach locations and topography. The hydrologic network also aids in illustrating the spatial patterns of predicted nutrient loads and sources contributed locally to each stream, and the percentages of nutrient load that reach Chesapeake Bay.

Delaware↗
PubMed2002

Social networks among older Australians: a validation of Glass's model.

BACKGROUND: The purpose of the study was to validate a set of measures of social networks that will be useful in epidemiological studies of the health of older persons. METHODS: Confirmatory factor analysis was used to test a multi-dimensional model of social networks. Data were drawn from The Australian Longitudinal Study of Ageing, conducted in the greater metropolitan area of Adelaide, South Australia. Participants were 1477 persons aged > or = 70 years who lived in the community or an institution and took part in the Australian Longitudinal Study of Ageing. Social networks with children, other relatives, friends and confidants were considered. Demographic indicators of gender, age group, income, education, marital status and place of residence were also measured, and social networks were compared for categories of these variables. RESULTS: Networks with children, relatives, friends and confidants were substantiated in these analyses. Differences in networks between categories of the demographic variables were evident. DISCUSSION: Adoption of the proposed measures will allow greater comparability between studies of older persons. This could lead to a better understanding of the effect of specific social networks upon health.

Aged↗
PubMed1992

Network range and health.

The inclusion of network concepts in the stress-distress model of health represents a major theoretical advance. Most researchers use the dyadic approach of social network analysis to construct network measures of social support. Working from the argument that network structure and social support are conceptually and empirically distinct, we extend the stress-distress model to include measures of network structure (network range) as predictors of exposure to stress, access to social support, and distress. We find that the density, diversity, and size dimensions of network range affect exposure to stress, access to social support, and distress differentially and that, in each case, their effects are gender-specific.

Adaptation, Psychological↗