Sequential configuration model for firing patterns in local neural networks

This paper presents a sequential configuration model to represent the coordinated firing patterns of memory traces in groups of neurons in local networks. Computer simulations are used to study the dynamic properties of memory traces selectively retrieved from networks in which multiple memory traces have been embedded according to the sequential configuration model. Distinct memory traces which utilize the same neurons, but differ only in temporal sequencing are selectively retrievable. Firing patterns of constituent neurons of retrieved memory traces exhibit the main properties of neurons observed in multi microelectrode recordings. The paper shows how to adjust relative synaptic weightings so as to control the disruptive influences of cross-talk in multipy-embedded networks. The theoretical distinction between (primarily anatomical) beds and (primarily physiological) realizations underlines the fundamentally stochastic nature of network firing patterns, and allows the definition of 4 degrees of clarity of retrieved memory traces.     

Modulation of endothelial fibronectin synthesis by polymorphonuclear granulocytes

The attachment of polymorphonuclear granulocytes (PMNs) to vascular endothelial cells occurs continually in normal tissues; however, knowledge of the factors that control leukocyte margination is incomplete. In the present study, we used cell cultures of pulmonary artery endothelium to study their interaction with PMNs. Endothelial cells were seeded in Costar 24-well plates following which PMNs were inoculated onto the endothelial monolayers and incubated for 2 to 20 hours. During this period, fibronectin synthesis by endothelial cells was estimated by ELISA. In wells to which PMNs had been added, supernatant fibronectin concentration was increased at all time points during the 20 hour incubation. At 20 hours, supernatants from wells to which PMNs had been added contained approximately 2 1/2 times the control level of fibronectin. Since the amount of fibronectin, as determined by ELISA, adsorbed onto the added PMNs was negligible, these data suggest that PMNs can modulate the synthesis of fibronectin by pulmonary artery cells. Pulse labeling experiments and measurements of endothelial intracellular fibronectin also suggest this possibility. The endothelial response does not appear to be owing to nonspecific physical interaction since similarly sized polystyrene beads did not cause any change in supernatant fibronectin levels while glutaraldehyde-fixed PMNs caused only a 20-25% increase in fibronectin levels.