Spectral characteristics of the mechanism of oxidase activity of ceruloplasmin

The absorbance and EPR spectra of type 1 and 2 copper-binding centres which are present in ceruloplasmin (Cp) molecule were shown to disappear upon the reduction of the enzyme by ascorbate under anaerobic conditions. The fluorescence band attributed to type 3 Cu was altered concomitantly. The electron-accepting nitroxyl radical added to reduced Cp restored the absorbance, EPR and fluorescence spectra of the oxidase. Only type 1 and 3 copper ions, as judged by spectral changes, can be reduced by ascorbate and then reoxidized by the nitroxyl radical in the azide-treated Cp. The spectral properties of Cp provided by copper ions of different types change simultaneously and concordantly upon oxidation/reduction. This seems to be caused by cooperative interaction of these ions involved in the electron transfer from the donating substrate to the accepting molecule of the nitroxyl radical (in model studies of oxidase reaction) or oxygen (under natural conditions). The copper ions in the active centre of Cp constitute an intramolecular electron transport chain, which may, at least in vitro, function without one of its links.     

Changes in the efficacy of transmission at synapses of the dorsal horn of the cat spinal cord observed during repetitive activation of cutaneous afferents

Inhibitory patterns in monosynaptic components of field potentials and potentials in the dorsal spinal cord surface were investigated during acute experiments on cats involving low-frequency stimulation of cutaneous peripheral nerves. Approximation of experimental data obtained from a theoretical plot was performed adopting a standard model of transmitter storage and release. Parameters of fractional release and replenishment of transmitter depleted from synaptic junctions were determined. Processes of replenishing supplies of transmitter for release were seen to intensify under rhythmic stimulation. A comparison between these experimental findings on the character of synapses of the monosynaptic reflex arc and others found in the literature indicated a similarity between the parameters of the mechanism underlying transmitter mobilization and release at different synaptic junctions formed by primary afferent fibers.Dnepropetrovsk State University Commemorating the 300th Aniversary of Ukraine-Russian Reunion, Dnepropetrovsk. Translated from Neirofiziologiya, Vol. 19, No. 4, pp. 491–497, July–August, 1987.     

Brain circuitry outside the synaptic cleft

A growing body of experimental evidence suggests that astroglia, and possibly microglia, play an important part in regulating synaptic networking of the brain. It has also emerged that extracellular matrix (ECM) structures that enwrap synaptic connections can generate molecular signals affecting both neuronal and glial activity. Thus it appears that the mechanism of information processing in the brain, which has hitherto been associated almost exclusively with neural circuits, could also involve informative signal exchange outside the synaptic cleft. In this Theme Issue, research teams including leading experts on astroglia–neuron communication and on ECM signalling report their recent findings, share their views and discuss future conceptual advances in the field. Potential implications for drug development and new therapeutic targets with regard to some common neurological conditions are discussed throughout the issue.     

Effect of the high dose/refuge strategy on Bt-crop yield dynamics (mathematical simulation)

A mathematical model is presented that describes interactions between Bt-crops and insect pests taking into account the plant growth rate, consumption of plant biomass by pests, suppression of insect proliferation by Bt toxins, emergence of Bt-resistant insects and their mixing with the wild type. It is shown that migration of Bt-susceptible insects from “refuge plots” onto the Bt-crop field invaded by resistance-carrying insects improves the yield dynamics; being high enough, this inflow eventually eliminates the resistant pest population.     

Analysis of commercial fish population size oscillations in Lake Peipus

With the use of recurrence plots, we show that the irregular oscillations in time, which commercial fish populations in Lake Peipus undergo, are deterministic.