Olfactory experience modifies the effect of odour on feeding behaviour in a goal-related manner

Natural food odours elicit different behavioural responses in snails. The tentacle carries an olfactory organ, and it either protracts toward a stimulating carrot odour or retraces in a startle-like fashion away from a cucumber odour. The tentacle retraction to cucumber was still present after the snails were fed cucumber during inter-trial periods. Also, snails without any food experience displayed a longer latency to the first bite of cucumber than of carrot and rejected cucumber more often. After tasting these foods, the latency to carrot was not affected while the latency to and number of rejections of cucumber decreased. These results suggest that initial repulsive features of food odour can be only partially compensated by olfactory learning and feeding experience. In the present study, we demonstrated that an invertebrate can be repulsed or attracted by the same natural odour at the same time and that these behavioural responses are likely aimed at achieving different physiologically relevant goals.     

Synthesis of cyclic analogues of loop 4 of nerve growth factor

Cyclic peptides cyclo(-Gly-Asp-Glu-Lys-), cyclo(-Gly-Gly-Asp-Glu-Lys-) and cyclo(-Gly-Gly-Gly-Asp-Glu-Lys-) were synthesized as models of theβ-turn of nerve growth factor loop 4. The corresponding protected linear precursors were obtained in 52–83% yields by the solid-phase method with the use of the Fmoc/Bu ^t strategy and a chlorotrityl anchor group. The cyclization was carried out with benzotriazolyloxytris(dimethylamino)phosphonium (BOP) hexafluorophosphate, N-[(1H-benzotriazole-1-yl)-(dimethylamino)methylene]-N-methylmetanaminium-N-oxide (HBTU) hexafluorophosphate, and diphenylphosphorylazide (DPPA) at a dilution of 10^?3 M. The distribution of reaction products was studied for each cyclopeptide in dependence on the type of the coupling agent. The use of DPPA was shown to completely inhibit the formation of cyclodimers in the synthesis of five-and six-membered cyclopeptides; however, in the case of a four-membered peptide, an additional tenfold dilution of the reaction mixture was necessary to achieve the effect. The identification of several byproducts during the synthesis showed that the elongation of the polypeptide chain using the BOP reagent can be complicated by substantial racemization, and the cleavage of the chlorotrityl anchor group by 0.5% TFA in dichloromethane proceeds with insufficient selectivity and is accompanied by the premature Boc deblocking of the lysine side function.     

ONTOGENETIC NICHE SHIFT IN THE BRACHIOPOD TEREBRATALIA TRANSVERSA: RELATIONSHIP BETWEEN THE LOSS OF ROTATION ABILITY AND ALLOMETRIC GROWTH

Abstract: Many articulated brachiopods experience marked life habit variations during ontogeny because they experience their fluid environment at successively higher Reynolds numbers, and they can change the configuration of their inhalant and exhalant flows as body size increases. We show that the extant brachiopod Terebratalia transversa undergoes a substantial ontogenetic change in reorientation governed by rotation around the pedicle. T. transversa′s reorientation angle (maximum ability to rotate on the pedicle) decreases during ontogeny, from 180 degrees in juveniles to 10–20 degrees in individuals exceeding 5 mm, to complete cessation of rotation in individuals larger than 10 mm. Rotation ability is substantially reduced after T. transversa achieves the adult lophophore configuration and preferred orientation with respect to ambient water currents at a length of 2.5–5 mm. We hypothesize that the rotation angle of T. transversa is determined mainly by the position of ventral and dorsal points of attachment of dorsal pedicle muscles relative to the pedicle. T. transversa shows a close correlation between the ontogenetic change in reorientation angle and ontogeny of morphological traits that are related to points of attachment of dorsal pedicle muscles, although other morphological features can also limit rotation in the adult stage. The major morphological change in cardinalia shape and the observed reduction of rotation affect individuals 2.5–10 mm in length. The position of ventral insertions of dorsal pedicle muscles remains constant, but contraction of dorsal pedicle muscles is functionally handicapped because dorsal insertions shift away from the valve midline, rise above the dorsal valve floor, and become limited by a wide cardinal process early in ontogeny (<5 mm). The rate of increase of cardinal process width and of distance between dorsal pedicle muscle scars substantially decreases in the subadult stage (5–10 mm), and most of the cardinalia shell traits grow nearly isometrically in the adult stage (>10 mm). T. transversa attains smaller shell length in crevices than on exposed substrates. The proportion of small‐sized individuals and population density is lower on exposed substrates than in crevices, indicating higher juvenile mortality on substrates prone to grazing and physical disturbance. The loss of reorientation ability can be a consequence of morphological changes that strengthen substrate attachment and maximize protection against biotic or physical disturbance (1) by minimizing torques around the pedicle axis and/or (2) by shifting energy investments into attachment strength at the expense of the cost involved in reorientation.     

Two-faced nitric oxide is necessary for both erasure and consolidation of memory

One of ways of nitric oxide (NO) influence on neuronal activity is S-nitrosylation, the covalent attachment of NO group to the thiol side chain of cysteine, changes function of existing proteins, inhibiting their normal role in physiological functions including memory. Influence of NO via GC activates intracellular signaling cascades and triggers increased synthesis ofproteins, influencing the memory. In the present paper we want to express and test the hypothesis that the NO is necessary both for erasure and development of memory. In our experiments in terrestrial snail Helix we tested the idea that NO besides well shown participation in memory development is involved in erasure/lockout of memory during relearning and reconsolidation.     

Derivatives of rhodamine 19 as mild mitochondria-targeted cationic uncouplers

A limited decrease in mitochondrial membrane potential can be beneficial for cells, especially under some pathological conditions, suggesting that mild uncouplers (protonophores) causing such an effect are promising candidates for therapeutic uses. The great majority of protonophores are weak acids capable of permeating across membranes in their neutral and anionic forms. In the present study, protonophorous activity of a series of derivatives of cationic rhodamine 19, including dodecylrhodamine (C(12)R1) and its conjugate with plastoquinone (SkQR1), was revealed using a variety of assays. Derivatives of rhodamine B, lacking dissociable protons, showed no protonophorous properties. In planar bilayer lipid membranes, separating two compartments differing in pH, diffusion potential of H(+) ions was generated in the presence of C(12)R1 and SkQR1. These compounds induced pH equilibration in liposomes loaded with the pH probe pyranine. C(12)R1 and SkQR1 partially stimulated respiration of rat liver mitochondria in State 4 and decreased their membrane potential. Also, C(12)R1 partially stimulated respiration of yeast cells but, unlike the anionic protonophore FCCP, did not suppress their growth. Loss of function of mitochondrial DNA in yeast (grande-petite transformation) is known to cause a major decrease in the mitochondrial membrane potential. We found that petite yeast cells are relatively more sensitive to the anionic uncouplers than to C(12)R1 compared with grande cells. Together, our data suggest that rhodamine 19-based cationic protonophores are self-limiting; their uncoupling activity is maximal at high membrane potential, but the activity decreases membrane potentials, which causes partial efflux of the uncouplers from mitochondria and, hence, prevents further membrane potential decrease.     

Interactions Outside the Proteinase-binding Loop Contribute Significantly to the Inhibition of Activated Coagulation Factor XII by Its Canonical Inhibitor from Corn

Activated factor XII (FXIIa) is selectively inhibited by corn Hageman factor inhibitor (CHFI) among other plasma proteases. CHFI is considered a canonical serine protease inhibitor that interacts with FXIIa through its protease-binding loop. Here we examined whether the protease-binding loop alone is sufficient for the selective inhibition of serine proteases or whether other regions of a canonical inhibitor are involved. Six CHFI mutants lacking different N- and C-terminal portions were generated. CHFI-234, which lacks the first and fifth disulfide bonds and 11 and 19 amino acid residues at the N and C termini, respectively, exhibited no significant changes in FXIIa inhibition (K_i = 3.2 ± 0.4 nm). CHFI-123, which lacks 34 amino acid residues at the C terminus and the fourth and fifth disulfide bridges, inhibited FXIIa with a K_i of 116 ± 16 nm. To exclude interactions outside the FXIIa active site, a synthetic cyclic peptide was tested. The peptide contained residues 20–45 (Protein Data Bank code 1BEA), and a C29D substitution was included to avoid unwanted disulfide bond formation between unpaired cysteines. Surprisingly, the isolated protease-binding loop failed to inhibit FXIIa but retained partial inhibition of trypsin (K_i = 11.7 ± 1.2 μm) and activated factor XI (K_i = 94 ± 11 μm). Full-length CHFI inhibited trypsin with a K_i of 1.3 ± 0.2 nm and activated factor XI with a K_i of 5.4 ± 0.2 μm. Our results suggest that the protease-binding loop is not sufficient for the interaction between FXIIa and CHFI; other regions of the inhibitor also contribute to specific inhibition.