The Morphological,Genetic and Physiological Characteristics of a Benthic Dinoflagellate of the Genus <Emphasis Type="Italic">Ostreopsis</Emphasis> Isolated from Coastal Waters of the Northwestern Sea of Japan

A previous molecular-genetic analysis of clonal cultures and single cells of Ostreopsis spp. that were isolated from Peter the Great Bay (the Sea of Japan) revealed three different genotypes according to the nucleotide sequences of ribosomal DNA (rDNA). Of these, Ostreopsis sp. 1 was earlier found only off the coast of Japan and described as being the most common and highly toxic. We have obtained further molecular evidence and have studied the morphological features of cells from one of the Ostreopsis strains with this genotype and some aspects of its growth at salinities of 24, 28, and 32‰. The results showed that in cells from the Russian coast of the Sea of Japan, the third apical (3') and the third precingular (3") plates do not adjoin one another, being separated by the elongated second apical (2') plate. Cells of Ostreopsis sp. 1 from the Russian coast are significantly larger than Ostreopsis sp. 1 cells with the same genotype from the coast of Japan. Salinity did not have a substantial effect on the growth of Ostreopsis sp. 1. The growth rate varied from 0.24 to 0.35 divisions per day, with maximum values at a salinity of 24‰. When salinity decreased to 24‰, the exponential growth phase was significantly extended and the maximum cell concentration doubled.     

Regulation of the Pore-Forming Activity of Cecropin A by Local Anesthetics

The influence of local anesthetics on the regulation of the channel-forming activity of the antimicrobial peptide cecropin A has been investigated. The mean current flowing through the single cecropin channels i_sc was determined, and steady-state transmembrane current induced by cecropin AI_∞ was measured. It has been shown that the introduction of 1 mM of bupivacaine, benzocaine or 0.3 mM of tetracaine into the membrane bathing solution results in a decrease in i_sc and I_∞. At the same time, the addition of 1 mM lidocaine or procaine to the membrane-bathing solutions does not lead to a significant change in i_sc and I_∞. Comparison of the absolute values and the sign of the change in the boundary potential of negatively charged membranes and relative changes of i_sc and I_∞ after addition of local anesthetics shows that neither parameter correlates with the membrane boundary potential. The results of studying the effect of tested local anesthetics on the phase transition of membrane lipids allow us to conclude that the observed changes of i_sc and I_∞ are due to modulation of the elastic properties of the membrane.     

Modeling of the structure of protein–DNA complexes using the data from FRET and footprinting experiments

We discuss the question of constructing three-dimensional models of DNA in complex with proteins using computer modeling and indirect methods of studying the conformation of macromolecules. We consider the methods of interpreting the experimental data obtained by indirect methods of studying the three-dimensional structure of biomolecules. We discuss some aspects of integrating such data into the process of constructing the molecular models of DNA–protein complexes based on the geometric characteristics of DNA. We propose an algorithm for estimating conformations of such complexes based on the information about the local flexibility of DNA and on the experimental data obtained by Forster resonance energy transfer (FRET) and hydroxyl footprinting. Finally, we use this algorithm to predict the hypothetical configuration of DNA in a nucleosome bound with histone H1.     

An increase in model lipid membrane fluidity as a result of local anesthetic action

The effect of local anesthetics on the permeability of phospholipid liposomes of different composition for calcein has been investigated. The local anesthetics tested included amides (lidocaine, prilocaine, mepivacaine, and bupivacaine) and esters (benzocaine, procaine, and tetracaine). The permeability of large monolamellar liposomes was assessed by monitoring the fluorescence of calcein leaking from the phospholipid vesicles. All tested amide anesthetics exerted negligible effects on the permeability of dioleylphosphocholine (DOPC) liposomes for the fluorescent marker. The most efficient in this group was did bupivacaine. Amides had a more pronounced effect on membranes in which 20 mol % of DOPC was replaced by tetraoleoylcardiolipin (TOCL). Benzocaine and procaine at concentration up to 100 mM did not affect the permeability of DOPC liposomes. Membrane permeability of DOPC liposomes was not affected by the addition of tetracaine to the final concentration of 2 mM, while the increase of anesthetic concentration up to 50 mM was accompanied by an increase in the intensity of fluorescence of calcein released from the vesicles, and addition of the anesthetic to the concentration of 100 mM caused by complete release of the marker incorporated by the liposomes. The threshold concentration of tetracaine initiating calcein leakage from vesicles that contained 20 mol % TOCL was 7 mM, and the concentration corresponding to 100% calcein leakage was 20 mM. Confocal fluorescence microscopy of giant monolamellar liposomes formed from an equimolar mixture of DOPC and tetramiristoylcardiolipin demonstrated the destruction of solid ordered domains at the presence of anesthetics, and its destructive capacity increasing in the following order: procaine ≈ mepivacaine < bupivacaine ? tetracaine. Variability of the depth of anesthetic incorporation into the membrane may account for the dissimilar effects of local anesthetics on liposomes.     

Thyroliberin-induced motor asymmetry as an indicator of the individual behavioral strategy of rats in a radial labyrinth

The individual peculiarities of functional changes in motor asymmetry determined by behavioral test in T-maze have been shown in experiments with rats (nonpedigree and line LATI). The application of thyroliberin (10 mkg/kg) causes and increases the left-side lateralization which introduces alteration in the individual strategy of the successive round of 12 rays of radial maze with food during solution of spatial orientation task.     

Borate promotes the formation of a complex between legume AGP‐extensin and Rhamnogalacturonan II and enhances production of Rhizobium capsular polysaccharide during infection thread development in Pisum sativum symbiotic root nodules

The capacity to bind to biomolecules is considered to be the basis for any physiological role of boron (B). Legume arabinogalactan protein‐extensin (AGPE), a major component of the infection thread matrix of legume nodules is a potential B‐ligand. Therefore, its role in infection threads development was investigated in Pisum sativum grown under B deficiency. Using the AGPE‐specific antibody MAC265, immunochemical analysis revealed that a 175 kDa MAC265 antigen was abundant in +B but much weaker in –B nodule extracts. A B‐dependent complex involving AGPE and rhamnogalacturonan II (RGII) could be co‐purified using anti‐RGII antiserum. Following fractionation of –B nodules, MAC265 antigens were mostly associated with the bacterial pellet. Immunogold staining confirmed that AGPE was closely associated with the surface of rhizobia in the lumen of threads in ?B nodules whereas in +B nodules, AGPE was separated from the bacterial surface by a sheath of capsular polysaccharide. Interestingly, colonies of rhizobia grown in free‐living culture without B developed low capsule production. Therefore, we propose that B could be important for apical growth of infection threads by strengthening thread wall through a B‐dependent AGPE‐RGII interaction and by promoting bacterial advance through a B‐dependent production of a stable rhizobial capsule that prevents AGPE attachment.