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PubMed1983

Morphological evidence of the shedding of chondrocytes from the articular surface in neonatal rats: relationship to the interlacunar network.

The superficial zone of the femoral head articular cartilage of 5- to 15-day old rats was examined by light and electron microscopy for evidence of shedding into the joint space. Chondrocytes deepest in the superficial zone were round, surrounded by a capsule, and connected to adjacent chondrocytes by the interlacunar network, whereas cells in the middle of the zone appeared similar but with less cytoplasm. At the circular surface, chondrocytes were small, with pyknotic nuclei and poorly defined organelles. These cells occasionally protruded from the articular surface but maintained at least partial connection with the network and their capsule. Depressions in the articular surface were lined with material similar to that of the network and were the only locations found where the network did not terminate at a cell surface. This static evidence suggested at least two hypotheses: 1) Degenerating chondrocytes moved up through the superficial zone to the articular surface and were shed into the joint space. This movement may be facilitated by the network as part of neonatal cartilage development. 2) During joint formation, the surface of the articular cartilage was eroded down to the chondrocytes, which were exposed to the joint fluid, causing cell degeneration, death, and shedding. Evidence of cell shedding was rarely seen after 2 weeks of age. Likewise, the interlacunar network disappeared from the superficial zone during this period. A physiological as well as structural relationship may exist between the chondrocytes and interlacunar network.

Animals↗

PubMed1991

Organization of the reticular network of rabbit Peyer's patches.

The organization of the network of collagen fibers of rabbit Peyer's patches was examined by scanning electron microscopy (SEM) in alkali-water macerated tissues. The relationship between this network and the reticular cells within it was further studied by SEM of ultrasonicated tissues. Collagen fibrils (about 60 nm in diameter) formed collagen fibers or sheets. There were sheets of collagen fibrils with numerous pores beneath the patch dome epithelium. Within the patches, collagen fibers repeatedly divided and fused, forming the reticular network. The reticular network within the follicle was looser than within the dome, the corona, or the interfollicular area. The latter three compartments showed similar structures and consisted of numerous intercommunicating small subcompartments. Reticular cells were in contact with groups of free cells lodged in these subcompartments within the reticular network. Reticular cell processes with numerous fenestrations embraced not only collage fibers forming the reticular network, but also sheaths of collagen fibers of blood and lymphatic vessels. Sheaths of collagen fibers of high endothelial venules and lymphatic vessels were also fenestrated, indicating the sites through which lymphocytes and other free cells migrate. These results indicate that the reticular network of Peyer's patches is organized so as to facilitate migration and lodging of free cells and thus facilitate antigen-to-cell and cell-to-cell interactions during an immune response. The naked areas on the collagen fibers seem to provide a scaffolding for free cells during their migration.

Animals↗

PubMed1994

Social network characteristics in fibromyalgia or rheumatoid arthritis.

PURPOSE: To describe trends in the personal social network characteristics of the fibromyalgia patients compared with the network of patients with another chronic disorder such as rheumatoid arthritis (RA). METHODS: A structured interview was applied to 10 fibromyalgia patients and 10 matched RA patients. RESULTS: The networks of the 10 fibromyalgia and 10 RA patients were comparable in most respects, namely: the small number of intimate friends, the reliance for support on the spouse and the physician, and the relative lack of new social contacts. Furthermore, the fibromyalgia networks were closed networks within a small geographic area. These networks lacked initiative to establish and maintain relations, and can hardly fulfill the patients' psychosocial needs. CONCLUSION: Based on small numbers, the study provides some evidence that social networks of patients with fibromyalgia are more restricted than those of RA patients. Further studies should include larger numbers of patients to clarify cause and effect relationships and to suggest new directions in the treatment of chronic disorders such as fibromyalgia.

Adolescent↗

PubMed1996

The social network characteristics of fibromyalgia patients compared with healthy controls.

OBJECTIVE: To assess structural social network characteristics and perceived loneliness in fibromyalgia syndrome (FMS) patients and healthy controls. METHODS: A cross-sectional, retrospective, case-control design was employed using a structured interview and a self-report questionnaire. We studied 25 female FMS patients and 25 matched healthy female controls. RESULTS: FMS patients had statistically significantly (P < 0.05) more intimate friends (mean 4.5) and more health care providers (mean 1.5) than did controls (2.3 and 0.0, respectively). The FMS patients more often initiated the contact with family members (mean 2.1) than did controls (mean 0.8). FMS patients did not perceive themselves as lonelier than controls perceived themselves. While there was a significant negative correlation between loneliness and social network variables among the controls, this relationship was not significant among the FMS patients. Among the patients, there was a strong correlation between the total social network size and the number of intimate friends, whereas in controls, the mean number of acquaintances was strongly correlated with the total network size. CONCLUSION: Compared to healthy controls, the social networks of FMS patients presented more linkages with intimate friends, family members, and health care providers. The lack of correlation between loneliness and social network variables for FMS patients is not what might be expected from social support theory. The assessment of structural social network characteristics along with social support variables may add to our understanding of the social functioning of FMS patients.

Adult↗

PubMed2004

Are there more than cross-sectional relationships of social support and support networks with functional limitations and psychological distress in early rheumatoid arthritis? the European Research on Incapacitating Diseases and Social Support Longitudinal Study.

OBJECTIVE: To investigate whether greater social support and support network are cross-sectionally associated with less functional limitations and psychological distress in patients with early rheumatoid arthritis (RA); whether this association is constant over time; and whether increases in social support or support network are associated with less functional limitations and psychological distress. METHODS: Subjects were from the European Research on Incapacitating Diseases and Social Support cohort and had early RA. Social support, support network, functional limitations (Health Assessment Questionnaire), and psychological distress (General Health Questionnaire) were assessed annually. Variance and covariance analyses with repeated measures were performed. RESULTS: A total of 542 subjects were assessed for 3 years. On average, patients with a greater amount of specific social support or a stronger specific support network experienced less functional limitation and less psychological distress. Changes in a given subject's functional limitations and psychological distress did not depend on his or her baseline social support or support network. Neither social support nor support network change over time. CONCLUSION: There may be a cross-sectional link between specific social support or support network and functional limitations and psychological distress, but no longitudinal association could be evidenced.

Adult↗

PubMed1995

Visualization of the transverse cytoskeletal network in insect-flight muscle by scanning-electron microscopy.

Located at the level of the Z-line, the transverse cytoskeletal network of insect-flight muscle interconnects adjacent myofibrils with one another, and interconnects peripheral myofibrils with the cell membrane. This network has been presumed to keep myofibrils in register, or to distribute tension laterally among myofibrils. In this study, we used scanning-electron microscopy to reveal details of the three-dimensional arrangement of this network. The network is seen to interconnect longitudinal elements of the cytoskeletal network which surround each myofibril. The arrangement is not unlike that seen in vertebrate skeletal muscle. Interestingly, the transverse network makes contact with cell components such as dense bodies and mitochondria. Such contacts imply potential roles over and above those noted above. The network may be involved not only in mechanical function, but possibly also in intracellular communication.

Animals↗

PubMed2003

Social networks and quality of life among female long-term colorectal cancer survivors.

BACKGROUND: The population of long-term colorectal cancer survivors in the United States continues to increase, but little is known about how they fare-physically, mentally, or socially-in the years after diagnosis. The current study examines female long-term colorectal cancer survivors' health-related quality of life (HRQoL) in relation to social networks. METHODS: A population-based sample of female colorectal cancer survivors (n = 726) residing in Wisconsin was recontacted approximately 9 years after the initial diagnosis. Of 443 women who were alive in 1999, 307 women completed a follow-up questionnaire. Analysis was conducted on 259 participants who completed the Medical Outcomes Study Short Form 36 Health Status Survey and a modified version of Berkman and Syme's Social Network Index. Using multivariate analyses, HRQoL summary scores were tested for associations with individual and composite measures of social networks, including marital/partner status; number of children, relatives, and friends; and the frequency of religious and community participation. RESULTS: After adjusting for age, extent of disease at diagnosis, number of comorbidities, body mass, and education, HRQoL was similar to norms published for the general population. Individual social network measures (including the number of relatives and friends) and composite network measures (including network size, the number of ties seen at least once per month, and overall social connectedness) were associated positively with mental health. CONCLUSIONS: Social networks may have an important relation with HRQoL-particularly mental health-among female long-term colorectal cancer survivors. The results of this study should be of interest to those seeking to understand or improve HRQoL among this growing population.

Adult↗

PubMed2003

Differential connections of the temporal pole with the orbital and medial prefrontal networks in macaque monkeys.

Previous studies indicate that the orbital and medial prefrontal cortex (OMPFC) is organized into "orbital" and "medial" networks, which have distinct connections with cortical, limbic, and subcortical structures. In this study, retrograde and anterograde tracer experiments in monkeys demonstrated differential connections between the medial and orbital networks and the dorsal and ventral parts of the temporal pole. The dorsal part, including dysgranular and granular areas (TGdd and TGdg), is reciprocally connected with the medial network areas on the medial wall and gyrus rectus (areas 10m, 10o, 11m, 13a, 14c, 14r, 25, and 32) and on the lateral orbital surface (areas Iai and 12o). The strongest connections are with areas 10m (caudal part), 14c, 14r, 25, 32, and Iai. The agranular temporal pole (TGa) is connected with several areas, but most strongly with medial network area 25. The granular area around the superior temporal sulcus (TGsts) and the ventral dysgranular and granular areas (TGvd and TGvg) are reciprocally connected with the orbital network (especially areas 11l, 13b, 13l, 13m, Ial, Iam, and Iapm). TGsts is strongly connected with the entire orbital network, whereas areas TGvd and TGvg have lighter and more limited connections. Intrinsic connections within the temporal pole are also restricted to dorsal or ventral parts. Together with evidence that the dorsal and ventral temporal pole are differentially connected to auditory and visual areas of the superior and inferior temporal cortex, the results indicate separate connections between these systems and the medial and orbital prefrontal networks.

Animals↗

PubMed1998

The effect of blob size and network dynamics on the size-based separation of polystyrenesulfonates by capillary electrophoresis in the presence of entangled polymer solutions.

This work focuses on the separation of standard polystyrenesulfonates (PSS), with molecular masses (Mr) between 16 and 990 x 10(3) in capillaries filled with semidilute (entangled) linear hydrophilic polymers. Contrary to cross-linked chemical gels, which produce permanent networks, solutions of linear polymers lead to dynamic networks. The analytical performances and migration mechanisms are discussed on the basis of experiments performed in solutions of linear polyethyleneoxides and derivatized celluloses of various molecular masses. The influence of the mesh size and of the lifetime of the obstacles of the separating network has been investigated in detail. The mesh size is assimilated to the blob size of the separating polymer and is a decreasing function of its concentration. The lifetime of the obstacles of the network, identified with the reptation time of the polymer chain, characterizes its dynamics. This characteristic time increases with both the molecular weight of the separating polymer and its concentration. Its impact was first examined at fixed blob size. Then, the influence of the blob size was studied while keeping the reptation time of the network constant. By doing so, the existence of interactions between the solute and the separating polymer or between the solute and capillary wall can be more safely assessed. It appears that the reptation time of the mesh has a large influence on the electrophoretic mobility of the PSSs under a threshold value, which is of the order of magnitude of the time taken by the PSS to migrate on the blob size. Also shown are separations using networks made up with mixtures of polyethyleneoxides of the same nature and same mass concentration, but of very different molecular masses. This latter approach allows one to adapt the viscosity of the solution and the dynamics of the network, keeping the blob size constant.

Electrophoresis, Capillary↗

PubMed2003

Learning networks in health and Parkinson's disease: reproducibility and treatment effects.

In a previous H(2) (15)O/PET study of motor sequence learning, we used principal components analysis (PCA) of region of interest (ROI) data to identify performance-related activation patterns in normal subjects and patients with Parkinson's disease (PD). In the present study, we determined whether these patterns predicted learning performance in subsequent normal and untreated PD cohorts. Using a voxel-based PCA approach, we correlated the changes in network activity that occurred during antiparkinsonian treatment and their relationship to learning performance. We found that the previously identified ROI-based patterns correlated with learning performance in the prospective normal (P < 0.01) and untreated PD (P < 0.05) cohorts. Voxel analysis revealed that target retrieval was related to a network characterized by bilateral activation of the dorsolateral prefrontal, premotor and anterior cingulate cortex, the precuneus, and the occipital association areas as well as the right ventral prefrontal and inferior parietal regions. Target acquisition was associated with a different network involving activation of the caudate, putamen, and right dentate nucleus, as well as the left ventral prefrontal and inferior parietal areas. Antiparkinsonian therapy gave rise to changes in retrieval performance that correlated with network modulation (P < 0.01). Increases in network activation and learning performance occurred with internal pallidal deep brain stimulation (GPi DBS); decrements in these measures were present with levodopa. Our findings suggest that network analysis of activation data can provide stable descriptors of learning performance. Network quantification can provide an objective means of assessing the effects of therapy on cognitive functioning in neurodegenerative disorders.

Adult↗

PubMed2003

Evaluation of thermal- and photo-crosslinked biodegradable poly(propylene fumarate)-based networks.

Biodegradable networks of poly(propylene fumarate) (PPF) and the crosslinking reagent poly(propylene fumarate)-diacrylate (PPF-DA) were prepared with thermal- and photo-initiator systems. Thermal-crosslinking was performed with benzoyl peroxide (BP), which is accelerated by N,N-dimethyl-p-toluidine (DMT) and enables injection and in situ polymerization. Photo-crosslinking was accomplished with bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO), which is activated by long-wavelength UV light and facilitates material processing with rapid manufacturing techniques, such as stereolithography. Networks were evaluated to assess the effects of the initiators and the PPF/PPF-DA double bond ratio on the mechanical properties. Regardless of the initiator system, the compressive properties of the PPF/PPF-DA networks increased as the double bond ratio decreased from 2 to 0.5. BAPO/UV-initiated networks were significantly stronger than those formed with BP/DMT. The compressive modulus of the photo- and thermal-crosslinked PPF/PPF-DA networks ranged from 310 +/- 25 to 1270 +/- 286 MPa and 75 +/- 8 to 332 +/- 89 MPa, respectively. The corresponding fracture strengths varied from 58 +/- 7 to 129 +/- 17 MPa and 31 +/- 13 to 105 +/- 12 MPa. The mechanical properties were not affected by the initiator concentration. Characterization of the network structures indicated that BAPO was a more efficient initiator for the crosslinking of PPF/PPF-DA, achieving a higher double bond conversion and crosslinking density than its BP counterpart. Estimated average molecular weights between crosslinks (Mc) confirmed the effects of the initiators and PPF/PPF-DA double bond ratio on the mechanical properties. This work demonstrates the capability to control the properties of PPF/PPF-DA networks as well as their versatility to be used as an injectable material or a prefabricated implant.

Biocompatible Materials↗

PubMed2006

The HOX genes are expressed, in vivo, in human tooth germs: in vitro cAMP exposure of dental pulp cells results in parallel HOX network activation and neuronal differentiation.

Homeobox-containing genes play a crucial role in odontogenesis. After the detection of Dlx and Msx genes in overlapping domains along maxillary and mandibular processes, a homeobox odontogenic code has been proposed to explain the interaction between different homeobox genes during dental lamina patterning. No role has so far been assigned to the Hox gene network in the homeobox odontogenic code due to studies on specific Hox genes and evolutionary considerations. Despite its involvement in early patterning during embryonal development, the HOX gene network, the most repeat-poor regions of the human genome, controls the phenotype identity of adult eukaryotic cells. Here, according to our results, the HOX gene network appears to be active in human tooth germs between 18 and 24 weeks of development. The immunohistochemical localization of specific HOX proteins mostly concerns the epithelial tooth germ compartment. Furthermore, only a few genes of the network are active in embryonal retromolar tissues, as well as in ectomesenchymal dental pulp cells (DPC) grown in vitro from adult human molar. Exposure of DPCs to cAMP induces the expression of from three to nine total HOX genes of the network in parallel with phenotype modifications with traits of neuronal differentiation. Our observations suggest that: (i) by combining its component genes, the HOX gene network determines the phenotype identity of epithelial and ectomesenchymal cells interacting in the generation of human tooth germ; (ii) cAMP treatment activates the HOX network and induces, in parallel, a neuronal-like phenotype in human primary ectomesenchymal dental pulp cells.

Adolescent↗

PubMed1981

Synaptic mechanisms that generate network oscillations in the absence of discrete postsynaptic potentials.

Synaptic mechanisms were examined in the pyloric network of the lobster stomatogastric which generate network oscillations in the absence of discrete postsynaptic potentials (PSPs). In normal saline, the unstimulated pyloric network underwent weak bursting in only a few cells. Stimulation of the input nerve, or bath application of the input neurotransmitter dopamine, produced similar vigorous bursting in many pyloric neurons. In saline-containing tetrodotoxin (TTX) plus dopamine, action potentials and corresponding discrete PSPs were blocked, but the underlying slow wave oscillations in network neurons continued. No oscillations occurred in TTX-saline without dopamine. The generation of these nonspiking network oscillations can be explained by the interaction between two synaptic mechanisms which do not produce discrete PSPs: neurotransmitter activation of bursting pacemaker oscillations in a single network neuron, and graded inhibition between network neurons.

Action Potentials↗

PubMed2006

Biodegradable network elastomeric polyesters from multifunctional aliphatic carboxylic acids and poly(epsilon-caprolactone) diols.

Biodegradable elastomeric network polyesters were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Yt) or meso-1,2,3,4-butanetetracarboxylic acid (Xb) and poly(epsilon-caprolactone) (PCL) diols with molecular weights of 530, 1,250 and 2,000 g.mol-1. Prepolymers prepared by a melt polycondensation were cast from DMF solution and postpolymerized at 280 degrees C for various periods of times to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. The network polyesters obtained were characterized by IR absorption spectra, WAXS, density measurement, DSC, and tensile test. YtPCL1250, and XbPCL1250 network polyester films showed good elastomeric properties with high ultimate elongation (540-590%), and low Young's modulus (2.5-3.3 MPa). The enzymatic degradation was estimated by the weight loss of network films in a buffer solution with Rhizopus delemar lipase at 37 degrees C. The degree and rate of degradation were significantly affected by the molecular weight of PCL diol, chemical structures of multifunctional aliphatic carboxylic acids and the morphology of network films. The changes in the solid states of network films during the degradation were also estimated by the results of DSC and WAXS. [see text]

Biocompatible Materials↗

PubMed2004

Functional and topological characterization of protein interaction networks.

The elucidation of the cell's large-scale organization is a primary challenge for post-genomic biology, and understanding the structure of protein interaction networks offers an important starting point for such studies. We compare four available databases that approximate the protein interaction network of the yeast, Saccharomyces cerevisiae, aiming to uncover the network's generic large-scale properties and the impact of the proteins' function and cellular localization on the network topology. We show how each database supports a scale-free, topology with hierarchical modularity, indicating that these features represent a robust and generic property of the protein interactions network. We also find strong correlations between the network's structure and the functional role and subcellular localization of its protein constituents, concluding that most functional and/or localization classes appear as relatively segregated subnetworks of the full protein interaction network. The uncovered systematic differences between the four protein interaction databases reflect their relative coverage for different functional and localization classes and provide a guide for their utility in various bioinformatics studies.

Algorithms↗

PubMed1993

Network incorporation of intermediate filament molecules differs between preexisting and newly assembling filaments.

When studying the way in which intermediate filaments assemble in vivo, it is important to distinguish between the incorporation of intermediate filament proteins into an existing intermediate filament network and the ability to form a new network within cells. To distinguish between these alternatives, we have made a hybrid construct consisting of the rod and tail domains of murine glial fibrillary acidic protein (GFAP) coupled to the head domain of bovine keratin 19, called K19GFAP. The assembly characteristics of K19GFAP were analyzed in vitro and in vivo. Replacement of the head domain with the bovine K19 sequence did not prevent the incorporation of K19GFAP into the existing network of vimentin intermediate filaments in NIH 3T3 cells but it was incompatible with de novo formation of filament networks in the epithelial cell line MCF-7, which lacks an endogenous vimentin network. By in vitro assembly studies, it was confirmed that K19GFAP was unable to assemble into typical intermediate filaments. We also investigated the ability of an appropriate type II keratin partner to rescue K19GFAP from incorporation into a vimentin network and initiate de novo filament assembly, using the fibroblast cell line KF-K8(3), an NIH 3T3 fibroblast cell line expressing a single human keratin, K8. The results confirm the importance of the coiled coil interactions in determining the fate of intermediate filament proteins. The results also emphasize that filament networks can not only tolerate but also incorporate assembly-deficient intermediate filament protein subunits.

3T3 Cells↗

PubMed2002

Using neural networks for (13)c NMR chemical shift prediction-comparison with traditional methods.

Interpretation of (13)C chemical shifts is essential for structure elucidation of organic molecules by NMR. In this article, we present an improved neural network approach and compare its performance to that of commonly used approaches. Specifically, our recently proposed neural network (J. Chem. Inf. Comput. Sci. 2000, 40, 1169-1176) is improved by introducing an extended hybrid numerical description of the carbon atom environment, resulting in a standard deviation (std. dev.) of 2.4 ppm for an independent test data set of approximately 42,500 carbons. Thus, this neural network allows fast and accurate (13)C NMR chemical shift prediction without the necessity of access to molecule or fragment databases. For an unbiased test dataset containing 100 organic structures the accuracy of the improved neural network was compared to that of a prediction method based on the HOSE code (hierarchically ordered spherical description of environment) using SPECINFO. The results show the neural network predictions to be of quality (std. dev. = 2.7 ppm) comparable to that of the HOSE code prediction (std. dev. = 2.6 ppm). Further we compare the neural network predictions to those of a wide variety of other (13)C chemical shift prediction tools including incremental methods (CHEMDRAW, SPECTOOL), quantum chemical calculation (GAUSSIAN, COSMOS), and HOSE code fragment-based prediction (SPECINFO, ACD/CNMR, PREDICTIT NMR) for the 47 (13)C-NMR shifts of Taxol, a natural product including many structural features of organic substances. The smallest standard deviations were achieved here with the neural network (1.3 ppm) and SPECINFO (1.0 ppm).

Journal Article↗

PubMed1998

Networks with side branching in biology.

There are many examples of branching networks in biology. Examples include the structure of plants and trees as well as cardiovascular and bronchial systems. In many cases these networks are self-similar and exhibit fractal scaling. In this paper we introduce the Tokunaga taxonomy for the side branching of networks and his parameterization of self-similar side-branching. We introduce several examples of deterministic branching networks and show that constructions with the same fractal dimension can have different side-branching parameters. As an example of stochastic-branching in biology we consider the vein structure of a leaf. We show that the vein structure of the leaf and river networks have nearly identical side branching statistics. We introduce diffusion limited aggregation (DLA) clusters. These clusters also exhibit Tokunaga side-branching statistics. We consider several alternative explanations for why leaves, river networks, and DLA clusters have similar side-branching statistics. We also consider the allometric scaling relation between metabolic rate and the mass of species in terms of a cardiovascular system with Tokunaga statistics. We find reasonably good agreement between the observed scaling exponent, approximately 0.75, and our model for a range of values of the fractal dimension of the network and the blood flow resistance parameter.

Blood Volume↗