Jörg D. Hardege

Seizure control by decanoic acid through direct AMPA receptor inhibition

See Rogawski (doi:10.1093/awv369) for a scientific commentary on this article.  The MCT ketogenic diet, an established treatment for drug-resistant epilepsy, leads to an elevation of plasma decanoic acid and ketones. Chang et al. show that decanoic acid, rather than ketones, provides anti-seizure activity in several ex vivo rat models of epilepsy, likely through the direct inhibition of AMPA receptors.

Stainless steel made to rust: a robust water-splitting catalyst with benchmark characteristics

The oxygen evolution reaction (OER) is known as the efficiency-limiting step for the electrochemical cleavage of water mainly due to the large overpotentials commonly used materials on the anode side cause. Since Ni–Fe oxides reduce overpotentials occurring in the OER dramatically they are regarded as anode materials of choice for the electrocatalytically driven water-splitting reaction. We herewith show that a straightforward surface modification carried out with AISI 304, a general purpose austenitic stainless steel, very likely, based upon a dissolution mechanism, to result in the formation of an ultra-thin layer consisting of Ni, Fe oxide with a purity >99%. The Ni enriched thin layer firmly attached to the steel substrate is responsible for the unusual highly efficient anodic conversion of water into oxygen as demonstrated by the low overpotential of 212 mV at 12 mA cm−2 current density in 1 M KOH, 269.2 mV at 10 mA cm−2 current density in 0.1 M KOH respectively. The Ni, Fe-oxide layer formed on the steel creates a stable outer sphere, and the surface oxidized steel samples proved to be inert against longer operating times (>150 ks) in alkaline medium. In addition Faradaic efficiency measurements performed through chronopotentiometry revealed a charge to oxygen conversion close to 100%, thus underpinning the conclusion that no “inner oxidation” based on further oxidation of the metal matrix below the oxide layer occurs. These key figures achieved with an almost unrivalled-inexpensive and unrivalled-accessible material, are among the best ever presented activity characteristics for the anodic water-splitting reaction at pH 13.

Peptide pheromones in female Nereis succinea.

Female specimen of the ragworm, Nereis succinea, employs a tetra-peptide, cysteinyl-glutathione (CSSG) as mate recognition and gamete release pheromone during reproduction. In the present study we review the role of peptide-based pheromones in Nereid worms focusing on pheromone production in females. New results demonstrate that the female ragworms produce the pheromone in the course of the oocyte maturation directly correlated to the oocyte diameter. Nevertheless, CSSG production is significantly increasing during the reproductive process, the nuptial dance, itself. The concentrations of the pheromone, nereithione (CSSG) and those of the possible precursors, reduced glutathione (GSH) and oxidized glutathione (GSSG), in the coelomic fluid were determined by HPLC showing that during spawning the female worms excrete 68.5 +/- 12.5 microg/h of the pheromone. GSH is mobilized, or synthesized and continuously converted into the pheromone enabling female N. succinea to maintain a constant level of pheromone release until the GSH reserves are depleted. Upon release CSSG induces not only gamete release in males but in doses as low as 10(-8) to 10(-9) M also significantly increases male swimming activity and as such may guide males towards the slower swimming females.

Scent marking pheromones in lizards: cholesterol and long chain alcohols elicit avoidance and aggression in male Acanthodactylus boskianus (Squamata: Lacertidae)

Femoral gland secretions are believed to play an important role in chemical communication and social organization of lizards. In spite of this, few studies have investigated the chemical composition and the behavioural roles of these secretions. The lacertid lizard Acanthodactylus boskianus is a good example, having these well-developed glands in both sexes. We used GC–MS chemical analysis of gland secretions and y-maze choice test bioassays to investigate the ability of the lizards to detect and respond to different synthetic blends made from compounds identified in the gland secretions. Based upon the GC–MS quantification data, we selected representatives of the main chemical groups (steroids, alcohols, acids, alkanes) detected in the lizard secretions and used these in a behavioural bioassay against controls. Males showed significant avoidance behaviour for cholesterol and alcohol blends, combined with agonistic behaviour towards these stimuli. Females did not show any significant selection to particular odour combinations. The data support the hypotheses that lizards can potentially use femoral gland secretions in chemical odour trails and utilize scent to mark territories and potentially also to establish dominance hierarchies. Cholesterol and long chain alcohols are suggested as potential candidates functioning as scent marking pheromones in A. boskianus.

Finding females: pheromone-guided reproductive tracking behavior by male Nereis succinea in the marine environment.

SUMMARY Pheromones trigger reproductive responses of many marine organisms, but little is known about how pheromones mediate mate-finding behavior in the marine environment. This paper investigates whether the tetrapeptide nereithione (cysteine-glutathione disulfide), known to be released by females of the polychaete Nereis succinea to trigger spawning in male N. succinea, can also be used at lower concentrations to guide males to the females. Low concentrations of pheromone elicited increased swim speed and turning left or right 84% of the time. Animals sometimes weaved back and forth, or in other cases swam straight along the trails an average of 8.1±1.2 cm before veering off. At higher concentrations, the males circled frequently, often encountering 10–20 cm of pheromone trail before swimming away. Male responses to nereithione were modeled by computer simulation, taking into account arousal of swim speed, activation of turning, speed of response and its decay, etc. In the model, low concentrations (<10–8 mol l–1) of pheromone significantly increased the number of encounters with the pheromone trail, an average following of simulated trails of 10.5±3.6 cm, and a significant increase in the frequency of encountering a virtual female on the trail (ANOVA, P<0.001). The model supports the hypothesis that a pheromone can have a dual function, with low concentration pheromone trails being used by male N. succinea to find females and increase their likelihood of mating whereas high concentrations of the same pheromone trigger the spawning behavior itself.

Simultaneously Hermaphroditic Shrimp Use Lipophilic Cuticular Hydrocarbons as Contact Sex Pheromones

Successful mating is essentially a consequence of making the right choices at the correct time. Animals use specific strategies to gain information about a potential mate, which is then applied to decision-making processes. Amongst the many informative signals, odor cues such as sex pheromones play important ecological roles in coordinating mating behavior, enabling mate and kin recognition, qualifying mate choice, and preventing gene exchange among individuals from different populations and species. Despite overwhelming behavioral evidence, the chemical identity of most cues used in aquatic organisms remains unknown and their impact and omnipresence have not been fully recognized. In many crustaceans, including lobsters and shrimps, reproduction happens through a cascade of events ranging from initial attraction to formation of a mating pair eventually leading to mating. We examined the hypothesis that contact pheromones on the female body surface of the hermaphroditic shrimp Lysmata boggessi are of lipophilic nature, and resemble insect cuticular hydrocarbon contact cues. Via chemical analyses and behavioural assays, we show that newly molted euhermaphrodite-phase shrimp contain a bouquet of odor compounds. Of these, (Z)-9-octadecenamide is the key odor with hexadecanamide and methyl linoleate enhancing the bioactivity of the pheromone blend. Our results show that in aquatic systems lipophilic, cuticular hydrocarbon contact sex pheromones exist; this raises questions on how hydrocarbon contact signals evolved and how widespread these are in the marine environment.

Interspecific activity of the sex pheromone of the European shore crab (Carcinus maenas)

The recent identification of uridine diphosphate (UDP) as the female sex-pheromone in the European shore crab Carcinus maenas demonstrated not only the link between moult and pheromone production, but also how it may have evolved from a ‘simple’ metabolic byproduct. Consequently, it is expected to be present in other moulting crustaceans, thus raising issues involving species specificity of the female pheromone. Bioassays were conducted using synthetic pheromone (UDP, 10 –3 –10 –4 M) to examine if it induced sexual behaviour in other crustacean species that are neither closely related nor occur in the same ecosystem. The snow crab, Chionoecetes opilio , and the yellowline arrow crab, Stenorhynchus seticornis , both belonging to a different superfamily (Majoidea) and occurring in different habitats than C. maneas (Portunoidea), displayed significant sexual behaviour towards UDP treated objects ( p < 0.005). These and other examples demonstrate that the female sex-pheromone UDP is not species-specific but is present and active in some other decapod crustaceans.

Oxidized Mild Steel S235: An Efficient Anode for Electrocatalytically Initiated Water Splitting

The surface of steel S235 was oxidized by Cl2 gas and checked for its electrocatalytic efficiency regarding oxygen formation in aqueous solution. If exposed to humid Cl2 gas for 110 min, steel S235 became an electrocatalyst that exhibits an overpotential for the oxygen evolution reaction (OER) of 462 mV at 1 mA cm(-2) at pH 7. The OER activity of the same sample at pH 13 was moderate (347 mV overpotential at 2.0 mA cm(-2) current density) in comparison with OER electrocatalysts developed recently. Potential versus time plots measured at a constant current demonstrate the sufficient stability of all samples under catalysis conditions at pH 7 and 13 for tens of hours. High-resolution X-ray photoelectron spectra could be reasonably resolved with the proviso that Fe2 O3 , FeO(OH), MnO(OH), and Mn2 O3 are the predominant Fe and Mn species on the surface of the oxidized steel S235.

Chemical Signal Mediated Premating Reproductive Isolation in a Marine Polychaete, Neanthes acuminata (Arenaceodentata)

Neanthes acuminata Ehlers (1868) is a monogamous coastal polychaete with male parental care and a high level of sexual selection. We measured the level of prezygotic isolation among allopatric populations of N. acuminata; from the East and West Coast of the USA, a population from Hawaii, and a laboratory culture originating from Los Angeles, CA. All populations were found to preferably mate with members of their own population. Individuals from populations from Atlantic vs. Pacific Ocean failed to pair and to mate, either during the 10 min or 48 hr experiments. Instead, individuals showed high levels of aggressive behavior. Experiments measuring the levels of interpopulation aggression, established that individuals can recognize and discriminate among different populations of N. acuminata on the basis of olfactory cues. Aggressive behavior was induced by exposure of animals to seawater “conditioned” by individuals from the other populations, thus demonstrating the role of olfaction in the detection of “home” populations. The aggressive display was stronger upon exposure to seawater conditioned with “unrelated” populations and especially between Pacific and Atlantic populations.

Ocean acidification affects marine chemical communication by changing structure and function of peptide signalling molecules.

Ocean acidification is a global challenge that faces marine organisms in the near future with a predicted rapid drop in pH of up to 0.4 units by the end of this century. Effects of the change in ocean carbon chemistry and pH on the development, growth and fitness of marine animals are well documented. Recent evidence also suggests that a range of chemically mediated behaviours and interactions in marine fish and invertebrates will be affected. Marine animals use chemical cues, for example, to detect predators, for settlement, homing and reproduction. But, while effects of high CO2 conditions on these behaviours are described across many species, little is known about the underlying mechanisms, particularly in invertebrates. Here, we investigate the direct influence of future oceanic pH conditions on the structure and function of three peptide signalling molecules with an interdisciplinary combination of methods. NMR spectroscopy and quantum chemical calculations were used to assess the direct molecular influence of pH on the peptide cues, and we tested the functionality of the cues in different pH conditions using behavioural bioassays with shore crabs (Carcinus maenas) as a model system. We found that peptide signalling cues are susceptible to protonation in future pH conditions, which will alter their overall charge. We also show that structure and electrostatic properties important for receptor binding differ significantly between the peptide forms present today and the protonated signalling peptides likely to be dominating in future oceans. The bioassays suggest an impaired functionality of the signalling peptides at low pH. Physiological changes due to high CO2 conditions were found to play a less significant role in influencing the investigated behaviour. From our results, we conclude that the change of charge, structure and consequently function of signalling molecules presents one possible mechanism to explain altered behaviour under future oceanic pH conditions.