Self-organized formation of a set of scaling filters and their neighbouring connections

A set of scaling feedforward filters is developed in an unsupervised way via inputting pixel-discretized extended objects into a winner-take-all artificial neural network. The system discretizes the input space by both position and size. Depending on the distribution of input samples and below a certain number of neurons the spatial filters may form groups of similar filter sizes with each group covering the whole input space in a quasi-uniform fashion. Thus a multi-discretizing system may be formed. Interneural connections of scaling filters are also developed with the help of extended objects. It is shown both theoretically and with the help of numerical simulation that competitive Hebbian learning is suitable for defining neighbours for the multi-discretizing system. Taking into account the neighbouring connections between filters of similar sizes only, i.e. within the groups of filters, the system may be considered as a self-organizing multi-grid system.     

Neuropeptides Control the Dynamic Behavior of Airway Mucosal Dendritic Cells

The airway mucosal epithelium is permanently exposed to airborne particles. A network of immune cells patrols at this interface to the environment. The interplay of immune cells is orchestrated by different mediators. In the current study we investigated the impact of neuronal signals on key functions of dendritic cells (DC). Using two-photon microscopic time-lapse analysis of living lung sections from CD11c-EYFP transgenic mice we studied the influence of neuropeptides on airway DC motility. Additionally, using a confocal microscopic approach, the phagocytotic capacity of CD11c⁺ cells after neuropeptide stimulation was determined. Electrical field stimulation (EFS) leads to an unspecific release of neuropeptides from nerves. After EFS and treatment with the neuropeptides vasoactive intestinal peptide (VIP) or calcitonin gene-related peptide (CGRP), airway DC in living lung slices showed an altered motility. Furthermore, the EFS-mediated effect could partially be blocked by pre-treatment with the receptor antagonist CGRP_8–37. Additionally, the phagocytotic capacity of bone marrow-derived and whole lung CD11c⁺ cells could be inhibited by neuropeptides CGRP, VIP, and Substance P. We then cross-linked these data with the in vivo situation by analyzing DC motility in two different OVA asthma models. Both in the acute and prolonged OVA asthma model altered neuropeptide amounts and DC motility in the airways could be measured. In summary, our data suggest that neuropeptides modulate key features motility and phagocytosis of mouse airway DC. Therefore altered neuropeptide levels in airways during allergic inflammation have impact on regulation of airway immune mechanisms and therefore might contribute to the pathophysiology of asthma.     

Enhanced K-cell activity in the peripheral blood of patients with malignant disease

Summary We have analysed the influence of human malignant, inflammatory and infectious disease on the capacity of peripheral lymphocytes to mediate antibody-dependent haemolysis. The application of an enzyme-like kinetic model for measurement of maximal cytotoxic function has permitted reproducible and sensitive determinations of the K-cell function. The results show that malignant disease is associated with enhancement of ADCC capacity.     

Daily and seasonal variations ofAlternaria andCladosporium airborne spores in León (North-West, Spain)

The spores ofAlternaria andCladosporium are present throughout the year in the atmosphere of León (NW Spain), although they show an important seasonal variation. To understand the relationship between the number of spores and climatic factors,Alternaria andCladosporium spores counts for January 1994 to December 1995 were examined by means of correlation analyses. The results of weekly samples of both years showed that the spores concentration of two taxa are significantly and positively correlated with maximum and minimum temperature and sunshine hours and negatively with relative humidity. The statistical analysis of daily samples generally showed the same results. In the hourly distribution of spore concentrations we can see a similar behaviour ofAlternaria andCladosporium, with most spores collected in the 12–14 h period.     

The role of phase shifts of sensory inputs in walking revealed by means of phase reduction

Detailed neural network models of animal locomotion are important means to understand the underlying mechanisms that control the coordinated movement of individual limbs. Daun-Gruhn and Tóth, Journal of Computational Neuroscience 31(2), 43–60 (2011) constructed an inter-segmental network model of stick insect locomotion consisting of three interconnected central pattern generators (CPGs) that are associated with the protraction-retraction movements of the front, middle and hind leg. This model could reproduce the basic locomotion coordination patterns, such as tri- and tetrapod, and the transitions between them. However, the analysis of such a system is a formidable task because of its large number of variables and parameters. In this study, we employed phase reduction and averaging theory to this large network model in order to reduce it to a system of coupled phase oscillators. This enabled us to analyze the complex behavior of the system in a reduced parameter space. In this paper, we show that the reduced model reproduces the results of the original model. By analyzing the interaction of just two coupled phase oscillators, we found that the neighboring CPGs could operate within distinct regimes, depending on the phase shift between the sensory inputs from the extremities and the phases of the individual CPGs. We demonstrate that this dependence is essential to produce different coordination patterns and the transition between them. Additionally, applying averaging theory to the system of all three phase oscillators, we calculate the stable fixed points - they correspond to stable tripod or tetrapod coordination patterns and identify two ways of transition between them.     

Interactions between plant hormones and thiol-related heavy metal chelators

Upon toxic metal stress numerous defence mechanisms have been induced, including the synthesis of metal-binding ligands and plant hormones or plant growth regulators in plants. As several elements in the promoter region of the heavy metal-responsive genes can be activated by plant hormones and growth regulators, understanding and revealing possible and special relationships between these regulator compounds and the metal chelator phytochelatins, which are in the first line of heavy metal defence mechanism is of great important. Phytochelatins are synthetized from glutathione and have a structure of [(γ-Glu-Cys)_n]-Gly, where n is the number of repetition of the (γ-Glu-Cys) units. Evidences for the role of PCs in heavy metal tolerance are very strong; however, little information is available on how plant growth regulators influence the phytochelatin synthesis at molecular or even gene expression level. In the present review we provide an overview of the role and synthesis of phytochelatins in metal-tolerance mechanism from a new point of view, i.e. their relation to the plant growth regulator molecules, with special regard also on those cases, when close direct relationship exists because of the partly overlapped synthesis pathways of plant growth regulators and glutathione/phytochelatins.