Magnetic Alignment in Carps: Evidence from the Czech Christmas Fish Market

While magnetoreception in birds has been studied intensively, the literature on magnetoreception in bony fish, and particularly in non-migratory fish, is quite scarce. We examined alignment of common carps (Cyprinus carpio) at traditional Christmas sale in the Czech Republic. The sample comprised measurements of the directional bearings in 14,537 individual fish, distributed among 80 large circular plastic tubs, at 25 localities in the Czech Republic, during 817 sampling sessions, on seven subsequent days in December 2011. We found that carps displayed a statistically highly significant spontaneous preference to align their bodies along the North-South axis. In the absence of any other common orientation cues which could explain this directional preference, we attribute the alignment of the fish to the geomagnetic field lines. It is apparent that the display of magnetic alignment is a simple experimental paradigm of great heuristic potential.     

Structural insight into the molecular basis of polyextremophilicity of short-chain alcohol dehydrogenase from the hyperthermophilic archaeon Thermococcus sibiricus

Biochemical analysis of enantioselective short-chain alcohol dehydrogenase from the hyperthermophilic archaeon Thermococcus sibiricus (TsAdh319) revealed unique polyextremophilic properties of the enzyme – half-life of 1 h at 100 °C, tolerance to high salt (up to 4 M) and organic solvents (50% v/v) concentrations. To elucidate the molecular basis of TsAdh319 polyextremophilicity, we determined the crystal structure of the enzyme in a binary complex with 5-hydroxy-NADP at 1.68 Å resolution. TsAdh319 has a tetrameric structure both in the crystals and in solution with an intersubunit disulfide bond. The substrate-binding pocket is hydrophobic, spacious and open that is consistent with the observed promiscuity in substrate specificity of TsAdh319. The present study revealed an extraordinary number of charged residues on the surface of TsAdh319, 70% of which were involved in ion pair interactions. Further we compared the structure of TsAdh319 with the structures of other homologous short-chain dehydrogenases/reductases (SDRs) from thermophilic and mesophilic organisms. We found that TsAdh319 has the highest arginine and aspartate + glutamate contents compared to the counterparts. The frequency of occurrence of salt bridges on the surface of TsAdh319 is the highest among the SDRs under consideration. No differences in the proline, tryptophan, and phenylalanine contents are observed; the compactness of the protein core of TsAdh319, the monomer and tetramer organization do not differ from that of the counterparts. We suggest that the unique thermostability of TsAdh319 is associated with the rigidity and simultaneous “resilience” of the structure provided by a compact hydrophobic core and a large number of surface ion pairs. An extensive salt bridge network also might maintain the structural integrity of TsAdh319 in high salinity.     

Neural control of olfaction and tentacle movements by serotonin and dopamine in terrestrial snail

We investigated the role of serotonin (5HT) and dopamine (DA) in the regulation of olfactory system function and odor-evoked tentacle movements in the snail Helix. Preparations of the posterior tentacle (including sensory pad, tentacular ganglion and olfactory nerve) or central ganglia with attached posterior tentacles were exposed to cineole odorant and the evoked responses were affected by prior application of 5HT or DA or their precursors 5-hydroxytryptophan (5HTP) and l-DOPA, respectively. 5HT applications decreased cineole-evoked responses recorded in the olfactory nerve and hyperpolarized the identified tentacle retractor muscle motoneuron MtC3, while DA applications led to the opposite changes. 5HTP and l-DOPA modified MtC3 activity comparable to 5HT and DA action. DA was also found to decrease the amplitude of spontaneous local field potential oscillations in the procerebrum, a central olfactory structure. In vivo studies demonstrated that injection of 5HTP in freely moving snails reduced the tentacle withdrawal response to aversive ethyl acetate odorant, whereas the injection of l-DOPA increased responses to “neutral” cineole and aversive ethyl acetate odorants. Our data suggest that 5HT and DA affect the peripheral (sensory epithelium and tentacular ganglion), the central (procerebrum), and the single motor neuron (withdrawal motoneuron MtC3) level of the snail’s nervous system.     

The influence of the electric diffusion potential on delayed fluorescence light curves of chloroplasts treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea

The potassium salt-induced transient increase of delayed fluorescence yield was studied in pea chloroplasts treated with 3-(3,4-dichlorophenyl)-1,1-dimethylurea.A simple kinetic model is proposed to account for the actinic light intensity dependence of the delayed fluorescence enhancement by the transmembrane diffusion potential induced by sudden salt addition. The electric field dependence of the rate constants for the recombination of primary separated charges with and without subsequent electronic excitation of reaction center chlorophyll was obtained.From the value of enhancement of delayed fluorescence by salt concentration gradients at saturating actinic light intensity, it is concluded that the distance, normal to thylakoid membrane surface, between the primary acceptor and the donor of Photosystem II is smaller than the membrane thickness.     

Soil chemical properties affect the concentration of elements (N,P, K,Ca, Mg,As, Cd,Cr, Cu,Fe, Mn,Ni, Pb,and Zn) and their distribution between organs of Rumex obtusifolius

Background and aims

The ionome (elemental composition) of grassland species has rarely been studied at the level of individual organs and little is known about effects of soil chemical properties on the ionome. Using the model oxalate plant Rumex obtusifolius, we asked how its biomass production and the distribution of elements between its organs is affected by soil chemical properties.

Methods

We established a pot experiment with R. obtusifolius planted in acidic non-contaminated control and in slightly acidic and alkaline soils anthropogenically contaminated by the risk elements As, Cd, Pb, and Zn. Both contaminated soils were untreated and treated by lime and superphosphate. We determined biomass production and the concentrations of elements in its organs.

Results

Biomass production was negatively related to the mobility of micro- and risk elements. Restricted transport of micro- and risk elements from belowground organs into leaves was recorded in untreated contaminated soils. In both lime-treated soils and in superphosphate-treated alkaline soil, elevated transport of micro- and risk elements from belowground organs into leaves was recorded in comparison to untreated contaminated soils. The lowest concentrations of micro- and risk elements were recorded in stems and seeds, followed by belowground organs and leaves.

Conclusions

R. obtusifolius is an As-, Cd-, Pb-, and Zn-excluder and is sensitive to high availability of micro- and risk elements in the soil. Soil chemical properties affect the distribution of essential elements within the plant greatly.     

Identification of bilirubin reduction products formed by Clostridium perfringens isolated from human neonatal fecal flora

Urobilinoids belong to the heterogenous group of degradation products of bilirubin formed in the gastrointestinal tract by intestinal microflora. Among them urobilinogen and stercobilinogen with their respective oxidation products, urobilin and stercobilin, are the most important compounds. The aim of present study was to analyze the products of bacterial reduction of bilirubin in more detail. The strain of Clostridium perfringens isolated from neonatal stools, capable of reducing bilirubin, was used in the study. Bacteria were incubated under anaerobic conditions with various native as well as synthetic bile pigments, including radiolabeled unconjugated bilirubin (UCB). Their reduction products were extracted from media and separated following thin layer chromatography. Pigments isolated were analyzed by spectrophotometry, spectrofluorometry and mass spectrometry. In a special set of experiments, bilirubin diglucuronide was incubated with either bacterial lysate or partially purified bilirubin reductase and beta-glucuronidase to reveal whether bilirubin glucuronides may be directly reduced onto conjugated urobilinoids. A broad substrate activity was detected in the investigated strain of C. perfringens and a series of bilirubin reduction products was identified. These products were separated in the form of their respective chromogens and further oxidized. Based on their physical-chemical properties, as well as mass spectra, end-catabolic bilirubin products were identified to belong to urobilinogen species. The reduction process, catalyzed enzymatically by the studied bacterial strain, does not proceed to stercobilinogen. Bilirubin diglucuronide is not reduced onto urobilinoid conjugates, glucuronide hydrolysis must precede double bond reduction and thus UCB is reduced much faster.     

Does Threat to the Nest Affect Incubation Rhythm in a Small Passerine?

Nest predation is a crucial factor influencing breeding success in birds. One possible way to protect nests is to modify parental activity in the vicinity of the nest. Here, we provide experimental evidence for an adjustment of incubation pattern during periods when there is an increased risk of nest predation in a small passerine. We compared the behaviour of incubating meadow pipit (Anthus pratensis) females during presentations of stuffed dummies of a nest predator (the magpie Pica pica) and a harmless intruder (the crossbill Loxia curvirostra) and during an undisturbed control incubation period. Females significantly decreased their activity in the presence of the nest predator. Specifically, after being flushed out, they returned to the nest later and moved to and from the nest less than when the harmless intruder was present. These results document the ability of birds to assess the nest predation risk and adjust their appropriate incubation strategy.