The vegetative network in the guinea pig and rat sacral spinal cords

The intermediate zones in the sacral segments of guinea pig and rat spinal cords are histochemically investigated for the presence of catecholaminergic and cholinergic structures. The presence of a well-developed noradrenergic network is demonstrated. This network connects the preganglionic vegetative nuclei in horizontal and vertical directions. In addition, only some fibers from the bundles composing this network show acetylcholinesterase activity.     

Neural network modelling of the influence of channelopathies on reflex visual attention

This paper introduces a model of Emergent Visual Attention in presence of calcium channelopathy (EVAC). By modelling channelopathy, EVAC constitutes an effort towards identifying the possible causes of autism. The network structure embodies the dual pathways model of cortical processing of visual input, with reflex attention as an emergent property of neural interactions. EVAC extends existing work by introducing attention shift in a larger-scale network and applying a phenomenological model of channelopathy. In presence of a distractor, the channelopathic network’s rate of failure to shift attention is lower than the control network’s, but overall, the control network exhibits a lower classification error rate. The simulation results also show differences in task-relative reaction times between control and channelopathic networks. The attention shift timings inferred from the model are consistent with studies of attention shift in autistic children.     

Neurofilamentous network and filamentous matrix preserved and isolated by different techniques from squid giant axon

The contribution of the neurofilamentous network to the structure of the squid giant axon was analyzed electron-microscopically. Axial 10-nm filaments cross-linked by radial 5-nm bridges form a network that is present in preparations prepared by a variety of techniques. The axoplasm is differentiated into dense and less dense regions. In the presence of Co(II) ions, the neurofilamentous network was remarkably well preserved and appeared to be associated with a dense web of fine filament matrix, which also was identified in extracted axoplasm and in fractions enriched with neurofilament protein complex. In the presence of La(III) ions, the neurofilamentous network had a coarse and open appearance. The stereo images of extracted and critical-point dried axoplasm suggested that the neurofilamentous network contains ordered lattice-like regions. Extracted preparations of extruded axoplasm and fractions enriched with neurofilament protein complex suggested that the properties of the network are determined by the neurofilament protein complex. It is proposed that the neurofilamentous network is the essential determinant of the form of the axon, and that the order within the network is determined by the radial components of the network. The structures observed in the different preparations are not artifacts, but rather are related closely to their native state in the axon.     

Synchrony with shunting inhibition in a feedforward inhibitory network

Recent experiments have shown that GABA_A receptor mediated inhibition in adult hippocampus is shunting rather than hyperpolarizing. Simulation studies of realistic interneuron networks with strong shunting inhibition have been demonstrated to exhibit robust gamma band (20–80 Hz) synchrony in the presence of heterogeneity in the intrinsic firing rates of individual neurons in the network. In order to begin to understand how shunting can contribute to network synchrony in the presence of heterogeneity, we develop a general theoretical framework using spike time response curves (STRC’s) to study patterns of synchrony in a simple network of two unidirectionally coupled interneurons (UCI network) interacting through a shunting synapse in the presence of heterogeneity. We derive an approximate discrete map to analyze the dynamics of synchronous states in the UCI network by taking into account the nonlinear contributions of the higher order STRC terms. We show how the approximate discrete map can be used to successfully predict the domain of synchronous 1:1 phase locked state in the UCI network. The discrete map also allows us to determine the conditions under which the two interneurons can exhibit in-phase synchrony. We conclude by demonstrating how the information from the study of the discrete map for the dynamics of the UCI network can give us valuable insight into the degree of synchrony in a larger feed-forward network of heterogeneous interneurons.     

Double-stranded nucleic acids in liquid-crystalline dispersions as building blocks for cross-linked supramolecular structures

Double-stranded DNA fixed in a cholesteric liquid-crystalline dispersion was used for generating an ordered supramolecular structure in the presence of anthracycline and copper (II) ions. The structure is stable in a water-salt solution and does not require poly(ethyleneglycol).The ordered network can be immobilized on the surface of a polymeric film, and may collapse in the presence of biologically and pharmacologically relevant compounds. Accordingly, the DNA-based liquid-crystalline network represents the basis to obtain novel highly sensitive biosensing units.     

Cover Picture

Confocal images of myoblasts containing a normal or a mutated desmin network. Desmin is stained in green, actin in red and nuclei in blue. The presence of the mutation (bottom panel) is responsible for the collapse of the desmin network into aggregates.     

THE GLYCOCALYX AND INITIATION OF EXINE SPINULES ON MICROSPORES OF CANNA

Spinules of Carina generalis pollen are initiated within a tridimensional network during the microspore tetrad period. The network is stained selectively with the hydrazide-silver proteinate method of Thiéry following periodate oxidation and by phosphotungstic acid at low pH, demonstrating the presence of polyanions. Protein is indicated as a component of the network by positive staining with PTA in acetone. These results suggest the presence of polysaccharides and proteins, possibly as mucopolysaccharides or glycoproteins. The network may be considered as a part of the glycocalyx because of its composition and association with the plasma membrane. Sporopollenin accumulates on the tridimensional network or in meshes of the net. The beaded fine structure of spinules resists the acetolysis mixture of Erdtman. Our results imply that the plasma membrane and its glycocalyx are part of the system which mediates genetic expression of exine form. The implication is compatible with formation of specific exines on all pollen grains of a plant and on aborted microspores, diminutive spores with depauperate chromosome complements, and enucleate bodies of cytoplasm resulting from meiotic abnormalities.     

From robustness to resilience: A network Price identity approach

We model a closed-loop network of agents distributed among subnetworks and study the sustainability of network structures in presence of random perturbations. The model outcomes show that the stability of compartmentalized networks built on uniform operators depends on perturbations on between-subnetwork coupling, while the stability of networks built on mutation operators depends on their assimilation capacity. Through the study of eigenvalues of the Laplacian, we succeed in measuring the degree of network robustness and resilience. Our results also permit to situate the Price theorem, both in its standard and expanded forms, in the context of network evolutionary variational identity.     

Revealing the F_actin Networks in Interphase Nuclei of Garlic Clove Cells by Confocal Fluorescence Microscopy

The interphase nuclei of parenchyma cells and epidermal cells of garlic (Allium sativum L.) clove were labelled with rabbit anti-actin antibody and FITC-conjugated goat anti-rabbit IgG antibody. The authors observed results with fluorescence microscopy and confocal laser scanning microscopy. The nuclei showed prominent green-yellow fluorescence, indicating the presence of actin in the nuclei. Fluorescence examination with TRITC-phalloidin showed distinctive red fluorescence in the nuclei, indicating that F-actin is present in the nuclei. Confocal laser scanning microscopy indicated the presence of F-actin containing network structures in the nuclei, but the network structures were absent and the nuclei still showed red fluorescence when the cells were treated with cytochalasin D before fixation; the red fluorescence in the nuclei was hard to be observed when the cells were treated with unlabelled phalloidin before the cells were stained with TRITC-phalloidin. These results indicate that F-actin is in the nuclei and forms network structures in the nuclei of garlic cells.     

Nanoparticle-induced assembly of hydrophobically modified chitosan

Hydrophobically modified chitosan (HMC) self-assembles in solution to form gels, making it suitable for applications in oil dispersion, hydrogel design and wound dressing. The self-assembly of HMC is driven by the association of hydrophobic moieties that are attached to chitosan monomers along the polymer chain. We present the results of discontinuous molecular dynamics simulations aimed at understanding how the length and density of the hydrophobic modification chains attached to HMC affect self-assembly and the structure of the resulting network. Long modification chains are required to promote the formation of a stable network in solution at a modification density of 5%; the networks form more readily at a modification density of 10%. The pore size distribution of the resulting HMC network is relatively independent of the modification chain length and density. Insertion of different sized hydrophobic nanoparticles into HMC has a significant impact on network formation, with the particles acting as junction points that promote the association of several HMC chains. The networks form faster in the presence of many small nanoparticles than in the presence of few large nanoparticles. We conclude that HMC could be a viable candidate to form hydrogels in solution.     

共聚焦荧光镜检术揭示大蒜鳞片细胞间期核中的F肌动蛋白网络

采用免疫荧光和荧光分子探针技术与共聚焦激光扫描显微镜观察相结合,对大蒜（Ａｌｌｉｕｍ ｓａｔｉｖｕｍ Ｌ．）鳞片细胞间期核中是否存在Ｆ肌动蛋白进行了研究。结果表明,以兔抗肌动蛋折抗体为一抗、ＦＴＴＧ－羊抗兔ＩｇＧ抗体为二抗进行免疫荧光标记实验,在荧光镜下观察到蒜瓣薄壁组织的细胞核及表皮细胞核均发出明亮的黄绿色荧光经共聚焦激光扫描显微镜进一步检查,整个细胞核呈黄绿色荧光,说明其中含有肌动蛋白。经ＴＲ     

Adhesion-guided multicellular assembly: a commentary upon the postulates, real and imagined, of the differential adhesion hypothesis, with special attention to computer simulations of cell sorting.

The condition for local dynamic stability of the trajectories of a metabolic network in the presence of conserved moieties and steady state subnetworks is given.     

Enzyme-catalyzed phase transition of alginate gels and gelatin-alginate interpenetrated networks

The enzyme-catalyzed gel-sol transition of calcium-alginate obtained by internal gelling strategy with the help of an entrapped alginate lyase is described. We show that alginate molecules and enzyme-produced oligoalginates shorten the gel time of physical gelatin gels (5% and 1.5%), probably due to local protein concentration increase. Interpenetrated networks composed of calcium-alginate and of gelatin were obtained only if elongation of gelatin helices inside a pre-existing calcium-alginate network could occur and only for low gelatin concentration (1.5%). The physical gelatin network is almost reversible inside the alginate one. Both networks can be obtained in the presence of alginate lyase, but gel-sol transition of calcium-alginate cannot be obtained in the presence of gelatin.     

Nuclear matrix network in Allium cepa

The presence of a nuclear matrix network in animal cells has been claimed by many workers in the last decade. The purpose of our study was to see whether a similar structure could be identified in the cells of higher plants. Our work revealed the presence of a fibrillar nonchromatinic network in Allium cepa nuclei. This could be impregnated with AgNO₃ in intact cells as well as in isolated matrices at the light microscope level. It was seen to be associated with the chromosomes from early to late prophase and also in telophase. Ultrastructurally a fibrillar network comparable to that reported earlier from animal cells was observed. This network remained associated with metaphase and anaphase chromosomes and could be digested with pepsin. Biochemical estimation of the isolated matrix revealed it to be made up mainly of proteins (more than 90%), traces of DNA (less than 1%) and a small quantity of RNA. SDS PAGE showed three polypeptide bands in the molecular weight range of 55,000–63,000 daltons.     

Protein aggregation as a paradigm of aging

The process of physiological decline leading to death of the individual is driven by the deteriorating capacity to withstand extrinsic and intrinsic hazards, resulting in damage accumulation with age. The dynamic changes with time of the network governing the outcome of misfolded proteins, exemplifying as intrinsic hazards, is considered here as a paradigm of aging. The main features of the network, namely, the non-linear increase of damage and the presence of amplifying feedback loops within the system are presented through a survey of the different components of the network and related cellular processes in aging and disease.     

Dynamic phase microscopy reveals periodic oscillations of endoplasmic reticulum during network formation

Dynamic phase microscopy was used to study the dynamic events of formation of the endoplasmic reticulum (ER) in interphase-arrested Xenopus egg extract. We have shown that the ER periodically oscillated in an ATP-dependent manner in the frequency range of 1.6–2.2 Hz, while the tubular membrane network formed in vitro. The spectral density, i.e. the pattern of a given frequency component in the Fourier spectrum, was strongly correlated with the dynamic events during microtubule-dependent and microtubule-independent ER network formation observed by video-enhanced contrast differential interference contrast and fluorescence microscopy. Because the 1.6–2.2 Hz frequency of oscillation during the network formation was detected both in the presence and absence of microtubules, it appears to be an intrinsic ATP-dependent ER membrane property. Several characteristic active and inactive stages of ER network formation were observed both in the presence and absence of microtubules. However, data analysis of these stages indicated that microtubules and dynein motor activity have a strong influence and a cooperative effect on the kinetics of ER formation by controlled fusion reaction.     

Effect of chromatin decondensation on the intranuclear matrix

We have studied the effect of chromatin condensation on the morphology of the residual structures isolated from rat liver nuclei. DNAse I digestion followed by high salt extraction of nuclei in the presence of Mg++ yields residual structures consisting of a dense peripheral layer surrounding an internal network, similar to those described by Berezney and Coffey [6]. These structures are stable at low ionic strength in the presence of EDTA. When nuclei swollen in EDTA are digested with DNAse II in the presence of EDTA, structures devoid of internal network are obtained even without subsequent treatment with high salt. When swollen nuclei are exposed to Mg++ a specific recondensation of chromatin takes place. The residual structures from recondensed nuclei are similar to those isolated from control nuclei in the presence of Mg++. The results suggest that the integrity and stability of the intranuclear matrix are acquired in the course of the isolation procedure and this is favoured by chromatin condensation.     

Mathematical modeling of the reproduction of the hepatitis C virus replicon in cell culture. Simulation of the action of potential therapeutics

Nowadays, search for efficient pharmaceuticals against hepatitis C virus (HCV) is an urgent task. In addition to conventional medicines, such as interferon and ribavirin, new specific drugs are being developed. Recently, it has been shown that a peptidomimetic substance, competitive inhibitor of viral NS3 protease, efficiently suppresses replication of the viral RNA replicon in Huh-7 cells. Computer simulation of the operation of the gene network comprising major processes of the viral RNA in the cell provides grounds for analysis of the HCV life cycle and search for key targets for efficient attack with drugs. The gene network of viral RNA replication in Huh-7 cells in the presence of a highly specific and efficient viral NS3 protease inhibitor has been reconstructed by analysis of reported experimental results and application of the GenNet technology. A mathematical model describing the operation of this network has been developed. The kinetics of the decrease in the level of viral RNA in the presence of the inhibitor predicted on the basis of this model is close to experimental results.     

Superprecipitation of actomyosin with p-chloromercuribenzoate-modified myosin reconstituted from rabbit skeletal muscle

Myosin head modified with p-chloromercuribenzoate (CMB) forms rigor-like complex with actin in the presence of ATP. Actomyosins with CMB-modified myosin were reconstituted to study the effect of rigor-like complexes on superprecipitation. As native myosin was increasingly replaced by CMB-modified myosin, superprecipitation of the actomyosin was strongly suppressed. Further, the suppression of superprecipitation occurred in a different fashion depending on how CMB-modified myosin was incorporated in myosin filaments of the reconstituted actomyosin. The present results indicate that superprecipitation requires the dissociation of actin and myosin head to take place (i.e., the presence of molecular rearrangements of actomyosin network), and further suggest that superprecipitation is associated with dynamic rearrangements of actomyosin network along myosin filaments.     

A model for a network of phosphorylation-dephosphorylation cycles displaying the dynamics of dominoes and clocks

We consider a model for a network of phosphorylation-dephosphorylation cycles coupled through forward and backward regulatory interactions, such that a protein phosphorylated in a given cycle activates the phosphorylation of a protein by a kinase in the next cycle as well as the dephosphorylation of a protein by a phosphatase in a preceding cycle. The network is cyclically organized in such a way that the protein phosphorylated in the last cycle activates the kinase in the first cycle. We study the dynamics of the network in the presence of both forward and backward coupling, in conditions where a threshold exists in each cycle in the amount of protein phosphorylated as a function of the ratio of kinase to phosphatase maximum rates. We show that this system can display sustained (limit-cycle) oscillations in which each cycle in the pathway is successively turned on and off, in a sequence resembling the fall of a series of dominoes. The model thus provides an example of a biochemical system displaying the dynamics of dominoes and clocks (Murray & Kirschner, 1989). It also shows that a continuum of clock waveforms exists of which the fall of dominoes represents a limit. When the cycles in the network are linked through only forward (positive) coupling, bistability is observed, while in the presence of only backward (negative) coupling, the system can display multistability or oscillations, depending on the number of cycles in the network. Inhibition or activation of any kinase or phosphatase in the network immediately stops the oscillations by bringing the system into a stable steady state; oscillations resume when the initial value of the kinase or phosphatase rate is restored. The progression of the system on the limit cycle can thus be temporarily halted as long as an inhibitor is present, much as when a domino is held in place. These results suggest that the eukaryotic cell cycle, governed by a network of phosphorylation-dephosphorylation reactions in which the negative control of cyclin-dependent kinases plays a prominent role, behaves as a limit-cycle oscillator impeded in the presence of inhibitors. We contrast the case where the sequence of domino-like transitions constitutes the clock with the case where the sequence of transitions is passively coupled to a biochemical oscillator operating as an independent clock.