Health state of native spruce stands and saplings in the northern timberline forests of the pechora basin

Trees in 10 types of northern timberline native spruce forests were studied for factors that determine their health state.     

Fixed focal-length optics in pulmonate snails (Mollusca, Gastropoda): squaring phylogenetic background and ecophysiological needs (II)

Abstract. Our results suggest that freshwater pulmonates like Lymnaea stagnalis, Radix peregra, Physa fontinalis , and Planorbarius corneus have inherited from their terrestrial ancestors eyes with a spherical, immobile lens with fixed focal-length optics. Unable to change the dioptric apparatus to form an image under water, modifications to the retina had to occur if sharp vision was required. Computer-assisted calculations and 3-D eye reconstructions demonstrate that the photoreceptors in the deeper, ventral pit are in a position to perceive focused images under water. Vision in air, however, would favour photoreceptive cells located in the shallower, dorsal pit. On the basis of histological, ethological, and optical comparisons, we conclude that the eyes in L. stagnalis and R. peregra , species that are known to escape and seek temporary refuge above the water surface, are well adapted to function in water as well as air, but that the eyes in P. fontinalis and Pl. corneus are less modified from those of their terrestrial ancestors. We also conclude that good resolving power may be of greater importance in the aquatic pulmonates than the terrestrial species, since the former have to locate thin, vertical stems of reeds and sedges to ascend in order to reach the surface to breathe.     

White storks Ciconia ciconia eavesdrop on mating calls of moor frogs Rana arvalis

Mating calls of animals are often detected by unintended receivers which use sexual signals to obtain information about the signaller. We investigated whether white storks Ciconia ciconia can eavesdrop mating calls of moor frogs Rana arvalis . White storks are dependent on moor frog abundance in early breeding season. Interspecific eavesdropping by predators is common and well documented in tropical anurans, whereas it is less known in temperate zone. We compared the frequency of approaches of white storks to loudspeakers when frog calls and the song thrush Turdus philomelos songs were simultaneously played back using the later as controls. The loudspeaker broadcasting the calls of male moor frogs clearly attracted white storks at 22 out of 84 nests. The bird songs attracted white storks in only one case. In 19 cases birds left the nest for unknown reasons which were considered as potential foraging movements. The results of this field experiment report a new case of eavesdropping on acoustic signals showing that advertisement calls of temperate moor frogs are an important stimulus for white storks.     

New approaches to the immunotherapy of Alzheimer's disease with the synthetic fragments of alpha7 subunit of the acetylcholine receptor

The effect of immunization with the synthetic fragments of the alpha7 subunit of the acetylcholine nicotine receptor on the spatial memory of mice subjected to olfactory bulbectomy, which causes the development of the neuro-degenetrative disease of Alzheimer's type, was studied. Mice of the NMRI line were immunized with the KLH conjugates of two peptide fragments of the N-terminal fragment of the alpha7 subunit extraxcellular fragment, subjected to olfactory bulbectomy to cause the development of the neurodegenetrative disease of Alzheimer's type, and then the state of the spartial memory was evaluated. It was shown that 20% of bulbectomized mice immunized with the N-terminal 1-23 fragment exhibited good spatial memory after training. Immunization with the peptide construct (159-167)-(179-188) consisting of two hydrophilic exposed regions of alpha7-subunit induced good spatial memory in 50% of bulbectomized mice, while in the control group, which received only KLH, none of the animals were educated. Thus, the development of immunotherapy with peptide (159-167)-(179-188) seems to be a promising approach to prophylaxis and treatment of Alzheimer's disease.     

Oxazolidinones mechanism of action: inhibition of the first peptide bond formation

Oxazolidinones are potent inhibitors of bacterial protein biosynthesis. Previous studies have demonstrated that this new class of antimicrobial agent blocks translation by inhibiting initiation complex formation, while post-initiation translation by polysomes and poly(U)-dependent translation is not a target for these compounds. We found that oxazolidinones inhibit translation of natural mRNA templates but have no significant effect on poly(A)-dependent translation. Here we show that various oxazolidinones inhibit ribosomal peptidyltransferase activity in the simple reaction of 70 S ribosomes using initiator-tRNA or N-protected CCA-Phe as a P-site substrate and puromycin as an A-site substrate. Steady-state kinetic analysis shows that oxazolidinones display a competitive inhibition pattern with respect to both the P-site and A-site substrates. This is consistent with a rapid equilibrium, ordered mechanism of the peptidyltransferase reaction, wherein binding of the A-site substrate can occur only after complex formation between peptidyltransferase and the P-site substrate. We propose that oxazolidinones inhibit bacterial protein biosynthesis by interfering with the binding of initiator fMet-tRNA(i)(Met) to the ribosomal peptidyltransferase P-site, which is vacant only prior to the formation of the first peptide bond.     

Modified water maze for studying spatial memory of rats

A method for evaluation of impairments of spatial memory in rats is put forward. Sensitivity of the advanced method based on the principles of Morris' water maze was compared with that of the classic prototype. Efficiency of the advanced method was assessed by dose- and time-dependent effects of agroclavine on the spatial memory of rats. Agroclavine (10 micrograms/kg) was shown to produce spatial memory impairment in rats. The obtained results also indicate that the modernized maze is more sensitive in revealing impairments of the spatial memory in rats than the classic water maze.     

Disruption of spatial memory in mice exposed to agroclavine

The results of the study of the mnemotropic activity of the ergot alkaloid agroclavine are presented. Effects of this substance administered in doses of 1, 10, 25, 50, and 200 micrograms/kg on learning and spatial memory were studied in a Morris water maze. Agroclavine had no effect on learning but sharply impaired the retention. This memory impairment persisted for 48 h after the agroclavine administration. Agroclavine treatment did not affect the ability of mice to learn and retain a new skill. Possible mechanisms of the agroclavine effect on memory are discussed.