Approach to studying the structure-activity relationship of native peptides. I. Structural organization of the opioid peptide Tyr-Glu-Gly-Phe-Met-Arg-Gly-Leu and its artificial analogs]

Theoretical conformational analysis was carried out for the octapeptide Tyr1-Gly2-Gly3-Phe4-Met5-Arg6-Gly7-Leu8. Possible structure of the opioid peptide under physiological conditions may be described by a set of low-energy conformations belonging to 14 different forms of the backbone. The solution of the "reverse conformational problem" for the opioid peptide enables one to predict the modified amino acid sequences (Ala2, D-Ala2, Ala3, D-Ala3, Ala7, D-Ala7, MeMet5, MeArg6-analogues) which may assume one of the low-energy states of the native hormone. The influence of the solute was not taken into account in our calculations.     

Regulation of growth and photosynthesis by Oscillatoria agardhii grown with a light/dark cycle

Abstract The cyanobacterium Oscillatoria agardhii was grown in turbidostat cultures with the light energy supply in either the continuous mode or in the pulsed mode (8/16 h light/dark (L/D) cycle). The light irradiance value used was sufficient to allow the maximal growth rate to be attained, when supplied continuously. Adaptation of O. agardhii to the L/D cycle was characterized by an increase in pigment content and photosynthetic performance, accompanied by a decrease in growth rate. This mode of adaptation resembled the adaptation of O. agardhii to continuous low light intensities. It is suggested that in this case the L/D cycle provokes this adaptation in order to allow the cells to accumulate carbohydrate rapidly during the light period. This was attributed to the storage of polyglucose, which served as a carbon and energy source for growth in the dark. The utilization of polyglucose in the dark was able to sustain the synthesis of all other cell components at the same rate as when cells were growing in the light. The growth yield in the dark, whilst metabolizing internally stored polyglucose, was 0.52 g cell C/g polyglucose C, or 0.62 g cell dry weight/g polyglucose. Although in the pulsed mode there is a 66% loss in light irradiance per 24 h when compared with a continuous light regime, the growth rate of the cyanobacteria grown in the pulsed mode was only 35% lower than the growth rate of a culture grown in continuous light. This can be explained by a high growth yield in the dark and by increased CO₂ fixation rates in the light of cells grown in the pulsed mode.     

K‐distribution three‐dimensional mapping of biological tissues in optical coherence tomography

Probability density function (PDF) analysis with K‐distribution model of optical coherence tomography (OCT) intensity signals has previously yielded a good representation of the average number of scatterers in a coherence volume for microspheres‐in‐water systems, and has shown initial promise for biological tissue characterization. In this work, we extend these previous findings, based on single point M‐mode or two‐dimenstional slice analysis, to full three‐dimensional (3D) imaging maps of the shape parameter α of the K‐distribution PDF. After selecting a suitably sized 3D evaluation window, and verifying methodology in phantoms, the resultant parametric α images obtained in different animal tissues (rat liver and brain) show new contrasting ability not seen in conventional OCT intensity images.      

Influence of the Background Noise on Recognition of Signals with a Complex Spectrum Structure in the Beluga Whale (<Emphasis Type="Italic">Delphinapterus leucas</Emphasis>)

The frequency resolving power of hearing (FRP) of the beluga whale Delphinapterus leucas was studied as dependent on influence of lasting low-intensity sounds (of the ultrasonic range from –20 to +10 dB). Testing of the spectrum ripple-phase reversal was used in conjunction with a noninvasive recording of auditory evoked potentials. FRP parameters were found to depend nonmonotonically on the intensity of the background noise. The resultant adaptation effects can be explained by the fact that, in response to the high-intensity signals, the auditory system sensitivity is reduced to the level optimal for analysis of these signals.     

Increasing temperature decreases the predatory effect of the intertidal shanny Lipophrys pholis on an amphipod prey

Interactions between Lipophrys pholis and its amphipod prey Echinogammarus marinus were used to investigate the effect of changing water temperatures, comparing current and predicted mean summer temperatures. Contrary to expectations, predator attack rates significantly decreased with increasing temperature. Handling times were significantly longer at 19° C than at 17 and 15° C and the maximum feeding estimate was significantly lower at 19° C than at 17° C. Functional‐response type changed from a destabilizing type II to the more stabilizing type III with a temperature increase to 19° C. This suggests that a temperature increase can mediate refuge for prey at low densities. Predatory pressure by teleosts may be dampened by a large increase in temperature (here from 15 to 19° C), but a short‐term and smaller temperature increase (to 17° C) may increase destabilizing resource consumption due to high maximum feeding rates; this has implications for the stability of important intertidal ecosystems during warming events.     

First Record of Fossil Ghost Pipefish (Solenostomidae,Gasterosteiformes) in Russia

A skeleton of a ghost pipefish (Solenostomidae) from the Pshekha Subformation of the Khadum Formation (Lower Oligocene) in the Republic of Adygea was discovered. This is the first fossil record of Solenostomidae in Russia; moreover, it is the only ghost pipefish found in the Oligocene. To date, only two fossil solenostomid genera and species from the Eocene of Monte Bolca (Italy) have been recorded. The only Recent genus of this family, Solenostomus Lacepède, 1903, contains four species. The new specimen is incompletely preserved; it lacks a fragment of the body and some fins, precluding the establishment of genus and species of this form. However, the unique geographical position and age of the new fossil expand our knowledge of the evolution and geographical range of the family Solenostomidae.     

Bidirectional variation in glutamate efflux in the medial prefrontal cortex induced by selective positive and negative allosteric mGluR5 modulators

Dysregulation of prefrontal cortical glutamatergic signalling via NMDA receptor hypofunction has been implicated in cognitive dysfunction and impaired inhibitory control in such neuropsychiatric disorders as schizophrenia, attention‐deficit hyperactivity disorder and drug addiction. Although NMDA receptors functionally interact with metabotropic glutamate receptor 5 (mGluR5), the consequence of this interaction for glutamate release in the prefrontal cortex (PFC) remains unknown. We therefore investigated the effects of positive and negative allosteric mGluR5 modulation on changes in extracellular glutamate efflux in the medial PFC (mPFC) induced by systemic administration of the non‐competitive NMDA receptor antagonist dizocilpine (or MK801) in rats. Extracellular glutamate efflux was measured following systemic administration of the positive allosteric mGluR5 modulator [S‐(4‐Fluoro‐phenyl)‐{3‐[3‐(4‐fluoro‐phenyl)‐[1,2,4]‐oxadiazol‐5‐yl]‐piperidin‐1‐yl}‐methanone] (ADX47273; 100 mg/kg, p.o.) and negative allosteric mGluR5 modulator [2‐chloro‐4‐{[1‐(4‐fluorophenyl)‐2,5‐dimethyl‐1H‐imidazol‐4‐yl]ethynyl}pyridine] (RO4917523; 0.3 mg/kg, p.o.), using a wireless glutamate biosensor in awake, freely moving rats. The effect of MK801 (0.03–0.06 mg/kg, s.c.) on mPFC glutamate efflux was also investigated in addition to the effects of MK801 (0.03 mg/kg, s.c.) following ADX47273 (100 mg/kg, p.o.) pre‐treatment. ADX47273 produced a sustained increase in glutamate efflux and increased the effect of NMDA receptor antagonism on glutamate efflux in the mPFC. In contrast, negative allosteric mGluR5 modulation with RO4917523 decreased glutamate efflux in the mPFC. These findings indicate that positive and negative allosteric mGluR5 modulators produce long lasting and opposing actions on extracellular glutamate efflux in the mPFC. Positive and negative allosteric modulators of mGluR5 may therefore be viable therapeutic agents to correct abnormalities in glutamatergic signalling present in a range of neuropsychiatric disorders.