Serotonin Modulates Oscillations of the Membrane Potential in Isolated Spinal Neurons from Lampreys

Studies were performed on spinal neurons from lampreys isolated by an enzymatic/mechanical method using pronase. The effects of 100 µM serotonin (5-HT) on membrane potential oscillations induced by a variety of excitatory amino acids were studied. 5-HT was found to depolarize branched cells (presumptive motoneurons and interneurons) by 2–6 mV without inducing membrane potential oscillations. However, when oscillations were already present because of an excitatory amino acid, 5-HT changed the parameters of these oscillations, increasing the amplitudes of all types of oscillations, increasing the frequency of irregular oscillations, and increasing the duration of the depolarization plateaus accompanied by action potentials. Serotonin modulation of the effects of excitatory amino acids and the electrical activity of cells in the neural locomotor network facilitates motor activity and leads to increases in the contraction of truncal muscles and more intense movements by the animal. The possible mechanisms of receptor coactivation are discussed, along with increases in action potential frequency and changes in the parameters of the locomotor rhythm

The Effects of Serotonin on Functionally Diverse Isolated Lamprey Spinal Cord Neurons

The experiments reported here showed that application of serotonin (5-hydroxytryptamine, 5-HT) (100 µ M) did not induce any significant current through the membranes of any of the spinal neurons studied (n = 62). At the same time, the membranes of most motoneurons and interneurons (15 of 18) underwent slight depolarization (2–6 mV) in the presence of 5-HT, which was not accompanied by any change in the input resistance of the cells. Depolarization to 10–20 mV occurred in some cells (3 of 18) of these functional groups, this being accompanied by 20–60% decreases in input resistance. The same concentration of 5-HT induced transient low-amplitude depolarization of most sensory spinal neurons (dorsal sensory cells), this changing smoothly to long-term hyperpolarization by 2–7 mV. The input resistance of the cell membranes in these cases showed no significant change (n = 8). Data were obtained which provided a better understanding of the mechanism by which 5-HT modulates the activity of spinal neurons. Thus, 5-HT facilitates chemoreceptive currents induced by application of NMDA to motoneurons and interneurons, while the NMDA responses of dorsal sensory cells were decreased by 5-HT. 5-HT affected the post-spike afterresponses of neurons. 5-HT significantly decreased the amplitude of afterhyperpolarization arising at the end of the descending phase of action potentials in motoneurons and interneurons and increased the amplitude of afterdepolarization in these types of cells. In sensory spinal neurons, 5-HT had no great effect on post-spike afterresponses. The results obtained here support the suggestion that 5-HT significantly modulates the activity of spinal neurons of different functional types. 5-HT facilitates excitation induced by subthreshold depolarization in motoneurons and some interneurons, facilitating the generation of rhythmic discharges by decreasing afterhyperpolarization. In sensory cells, 5-HT enhances inhibition due to hyperpolarization, suppressing NMDA currents. The differences in the effects of 5-HT on functionally diverse neurons are presumed to be associated with the combination of different types of 5-HT receptors on the membranes of these types of spinal neurons

Isolation and characterization of Agrobacterium strains from grapevines in Bulgarian vineyards and wild grapes, V. vinifera ssp. silvestris

Twenty strains of Agrobacterium spp. were isolated from grapevines derived from 9 different grape-growing regions in Bulgaria and from symptomless wild grapes, Vitis vinifera ssp. silvestris, naturally growing in forests of South-East Bulgaria. The isolated strains were examined by biochemical and pathogenicity tests and PCR analysis of chromosomal and plasmid-located genes. Two of the studied strains resemble non-pathogenic A. tumefaciens, but the others were determined as tumorigenic A. vitis. Only one out of 18 A. vitis strains, isolated from grapevines, was found to harbor vitopine Ti plasmid type. Surprisingly, all 4 A. vitis strains isolated from symptomless V. vinifera ssp. silvestris plants, proved to be tumorigenic. Thus, for the first time we report the isolation of pathogenic A. vitis strains from wild grapes. The strict correlation between the results from biochemical and virulence tests and PCR analysis suggests that the chosen PCR procedures can be used efficiently for direct PCR testing for the presence and tumorigenicity of A. vitis in grapevines.

Genetic diversity of Agrobacterium vitis strains, isolated from grapevines and wild grapes in Bulgaria, assessed by Cleaved Amplified Polymorphic Sequences analysis of 16S-23S rDNA

Nineteen tumorigenic Agrobacterium vitis strains isolated from commercial vineyards and wild grapes at different locations in Bulgaria were studied in relation to the Ti plasmid type and chromosomal background. The PCR analysis showed that all but one of the strains harbor an octopine/cucumopine type of Ti plasmid and one carries a vitopine type. The genetic diversity among the studied strains and 20 more A. vitis strains originating from different geographic regions in Europe, Asia, USA and South Africa was assessed by Cleaved Amplified Polymorphic Sequences (CAPS) analysis of 16S-23S rDNA region. The comparison of the obtained CAPS profiles and performed cluster analysis showed a high level of polymorphism among the studied strains distributed in totally 15 different groups within two main clusters. All Bulgarian strains are located in only three groups within one of the clusters. A high level of correlation between the chromosomal background and type of the carried Ti plasmids was found. The performed CAPS analysis demonstrated that all A. vitis strains isolated from wild grapes (V. vinifera ssp. silvestris) showed CAPS profiles identical with a number of strains isolated from commercial vineyards from different vine-growing regions in Bulgaria. A possible origin of this group of strains from an ancestral A. vitis strain, which initially inhabits wild grapes (V. vinifera ssp. silvestris) and later has been disseminated to cultivated grapevines is proposed

Crystal structure and oxygen content of the double perovskites GdBaCo 2-xFexO6-δ

The iron solubility limit, x, in GdBaCo2-xFexO 6-δ determined by means of X-ray diffraction was found to be close to 0.65 in air. The crystal structure changes of the double perovskites GdBaCo2-xFexO6-δ (x=0-0.6) were studied by means of in situ X-ray diffraction in temperature range from 25 to 900 °C in air. The oxygen content, 6-δ, was determined for these double perovskites in air as a function of temperature by means of thermogravimetric technique in range 25≤T, °C≤ 1100. The Pmmm-P4/mmm structure transition was found to occur in GdBaCo2-xFexO 6-δ (0≤x≤0.4) with increasing temperature. This transition is observed at the same temperature for the compositions with 0≤x≤0.1 while the transition temperature reaches maximum for x=0.2 and that decreases linearly with further iron increase. The double perovskite GdBaCo1.4Fe0.6O6-δ was shown to have the tetragonal P4/mmm structure at room temperature. The P4/mmm-Pmmm structure transition occurs at temperature as low as 170 °C for this double perovskite while reverse one is already observed at 290 °C in air. The Pmmm-P4/mmm structure transition was found to be strongly related to the oxygen content for the undoped and slightly doped (x≤0.2) double perovskites while there is no such relation for the double perovskites enriched by iron (x≥0.2). © 2012 Elsevier Inc. All rights reserved

Genotyping of Bulgarian Vitis vinifera L. cultivars by microsatellite analysis

A characterization of the Bulgarian grapevine genepool (Vitis vinifera L. cultivars) was initiated through microsatellite analysis. Seventy four wine and table grapevine varieties from the National List of Cultivars, were analyzed at 9 microsatellite loci: VVS2, ssrVvUCH11, ssrVvUCH 29, ssrVrZAG21, ssrVrZAG47, ssrVrZAG62, ssrVrZAG64, ssrVrZAG79 and ssrVrZAG83. The high genetic diversity (78 %) allowed accurate identification and discrimination of the cultivars. The low PI value (1.201 x 10-8) reflects the high discriminative power of the chosen set of markers for the investigated population. Based on the microsatellite allele data, two pairs of old native varieties, Misket Cherven and Misket Vrachanski; Tamyanka and Tamyanka tvarda, were considered distinct cultivars. The synonymy ofTamyanka, Italian Moscato Bianco and Greek Moschato Kerkyras andPamid and Greek Pamidi was verified, while the putative synonymy of Mavrud and Greek Mavroudi Arachovis was rejected.Further utilization of microsatellite profiling in the management of the Bulgarian grapevine genepool is discussed.

Thermoelectric behavior of BaZr0.9Y0.1O3−d proton conducting electrolyte

BaZr0.9Y0.1O3-δ (BZY10), a promising proton conducting material, exhibits p-type conduction under oxidative conditions. Holes in BZY10 are of the small polaron type. However, there is no clear understanding at which places in the lattice they are localized. The main objectives of this work were, therefore, to discuss the nature of electronic defects in BZY10 on the basis of the combined measurements of the thermo-EMF and conductivity. Total electrical conductivity and Seebeck coefficient of BZY10 were simultaneously studied depending on partial pressures of oxygen (pO2), water (pH2O) and temperature (T). The model equation for total conductivity and Seebeck coefficient derived on the basis of the proposed defect chemical approach was successfully fitted to the experimental data. Transference numbers of all the charge carriers in BZY10 were calculated. The heat of transport of oxide ions was found to be about one half the activation energy of their mobility, while that of protons was almost equal to the activation energy of their mobility. The results of the Seebeck coefficient modeling indicate that cation impurities, rather than oxygen sites, should be considered as a place of hole localization. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.Russian Science Foundation, RSF: 18-73-00022Funding: This work was supported by the Russian Science Foundation (project No. 18-73-00022