Hub and switches: endocannabinoid signalling in midbrain dopamine neurons

The last decade has provided a wealth of experimental data on the role played by lipids belonging to the endocannabinoid family in several facets of physiopathology of dopamine neurons. We currently suggest that these molecules, being intimately connected with diverse metabolic and signalling pathways, might differently affect various functions of dopamine neurons through activation not only of surface receptors, but also of nuclear receptors. It is now emerging how dopamine neurons can regulate their constituent biomolecules to compensate for changes in either internal functions or external conditions. Consequently, dopamine neurons use these lipid molecules as metabolic and homeostatic signal detectors, which can dynamically impact cell function and fitness. Because dysfunctions of the dopamine system underlie diverse neuropsychiatric disorders, including schizophrenia and drug addiction, the importance of better understanding the correlation between an unbalanced endocannabinoid signal and the dopamine system is even greater. Particularly, because dopamine neurons are critical in controlling incentive-motivated behaviours, the involvement of endocannabinoid molecules in fine-tuning dopamine cell activity opened new avenues in both understanding and treating drug addiction. Here, we review recent advances that have shed new light on the understanding of differential roles of endocannabinoids and their cognate molecules in the regulation of the reward circuit, and discuss their anti-addicting properties, particularly with a focus on their potential engagement in the prevention of relapse.     

Lack of sex‐specific movement patterns in an alien species at its invasion front – consequences for invasion speed

Efficient targeting of actions to reduce the spread of invasive alien species relies on understanding the spatial, temporal, and individual variation of movement, in particular related to dispersal. Such patterns may differ between individuals at the invasion front compared to individuals in established and dense populations due to differences in environmental and ecological conditions such as abundance of conspecifics or sex‐specific dispersal affecting the encounter rate of potential mates. We assessed seasonal and diurnal variation in movement pattern (step length and turning angle) of adult male and female raccoon dog at their invasion front in northern Sweden using data from Global Positioning System (GPS)‐marked adult individuals and assessed whether male and female raccoon dog differed in their movement behavior. There were few consistent sex differences in movement. The rate of dispersal was rather similar over the months, suggesting that both male and female raccoon dog disperse during most of the year, but with higher speed during spring and summer. There were diurnal movement patterns in both sexes with more directional and faster movement during the dark hours. However, the short summer nights may limit such movement patterns, and long‐distance displacement was best explained by fine‐scale movement patterns from 18:00 to 05:00, rather than by movement patterns only from twilight and night. Simulation of dispersing raccoon dogs suggested a higher frequency of male–female encounters that were further away from the source population for the empirical data compared to a scenario with sex differences in movement pattern. The lack of sex differences in movement pattern at the invasion front results in an increased likelihood for reproductive events far from the source population. Animals outside the source population should be considered potential reproducing individuals, and a high effort to capture such individuals is needed throughout the year to prevent further spread.     

The psychology of cooperation: Insights from chimpanzees and children

Across all cultures, humans engage in cooperative activities that can be as simple as preparing a meal or sharing food with others and as complex as playing in an orchestra or donating to charity. Although intraspecific cooperation exists among many other animal species, only humans engage in such a wide array of cooperative interaction and participate in large‐scale cooperation that extends beyond kin and even includes strangers.     

Alternative photosynthetic electron flow to oxygen in marine Synechococcus

Cyanobacteria dominate the world's oceans where iron is often barely detectable. One manifestation of low iron adaptation in the oligotrophic marine environment is a decrease in levels of iron-rich photosynthetic components, including the reaction center of photosystem I and the cytochrome b₆f complex [R.F. Strzepek and P.J. Harrison, Photosynthetic architecture differs in coastal and oceanic diatoms, Nature 431 (2004) 689-692.]. These thylakoid membrane components have well characterised roles in linear and cyclic photosynthetic electron transport and their low abundance creates potential impediments to photosynthetic function. Here we show that the marine cyanobacterium Synechococcus WH8102 exhibits significant alternative electron flow to O₂, a potential adaptation to the low iron environment in oligotrophic oceans. This alternative electron flow appears to extract electrons from the intersystem electron transport chain, prior to photosystem I. Inhibitor studies demonstrate that a propyl gallate-sensitive oxidase mediates this flow of electrons to oxygen, which in turn alleviates excessive photosystem II excitation pressure that can often occur even at relatively low irradiance. These findings are also discussed in the context of satisfying the energetic requirements of the cell when photosystem I abundance is low.     

How is human cooperation different?

Although cooperation is a widespread phenomenon in nature, human cooperation exceeds that of all other species with regard to the scale and range of cooperative activities. Here we review and discuss differences between humans and non-humans in the strategies employed to maintain cooperation and control free-riders. We distinguish forms of cooperative behaviour based on their influence on the immediate payoffs of actor and recipient. If the actor has immediate costs and only the recipient obtains immediate benefits, we term this investment. If the behaviour has immediate positive effects for both actor and recipient, we call this a self-serving mutually beneficial behaviour or mutual cooperation. We argue that humans, in contrast to all other species, employ a wider range of enforcement mechanisms, which allow higher levels of cooperation to evolve and stabilize among unrelated individuals and in large groups. We also discuss proximate mechanisms underlying cooperative behaviour and focus on our experimental work with humans and our closest primate relatives. Differences in the proximate mechanisms also seem to contribute to explaining humans'' greater ability to cooperate and enforce cooperation.     

Supramolecular Assembly and Function of Subunits Associated with the Chlorophyll a-b Light-Harvesting Complex II (LHC II) in Soybean Chloroplasts

The chlorophyll (Chl) a-b light harvesting complex II (LHC II)contains more than 80% of the light-harvesting pigments of photosystemII (PS II) in chloroplasts. The supramolecular assembly andfunction of this auxiliary antenna system was investigated inChi b-deficient and Chi b-less mutant chloroplasts from soybeanand barley plants, and in their wild-type counterparts. Fourdistinct LHC II polypeptides were resolved by SDS-PAGE (subunitsa, b, c and d), having apparent molecular masses of 29, 28,27.2 and 26.8 kDa, respectively. The analysis of LHC II subunitcomposition in different developmental stages of the PS II unitin soybean (3>Chla/Chlbb>6), indicated the associationof specific subunits with the LHC H-inner and LHC II-peripheralin the chloroplast. The amount of subunit a in PS II was constantover a broad range of Chl a/Chl b ratios, suggesting that thissubunit is closely associated with the PS II-core complex. Subunitd also appeared to be constant over a wide range of Chl a/Chlb ratios, suggesting close association with the LHC II-inner.The PS II content in subunits b and c increased with the PSII antenna development in soybean but the ratio of b/c remainedconstant in all developmental stages and equal to 2 :1. Subunita was present in the Chl b-less chlorina f2 mutant of barleygrown under continuous illumination but was absent under intermittentillumination. The results suggest that each subunit binds 13-15Chl molecules. A working hypothesis is presented on the PS IIantenna development and LHC II subunit composition in soybeanchloroplasts. (Received October 11, 1988; Accepted January 19, 1989)     

Effect of dopamine agonists and antagonists on DOPA formation in the substantia nigra

Abstract: The effect of different psychotropic drugs on the rate of DOPA accumulation after administration of a decarboxylase inhibitor (NSD 1015) was compared in the substantia nigra (SN) and caudate nucleus (CN) by a new radioenzymatic method. Inhibition of monoamine oxidase with pargyline or stimulation of dopamine (DA) receptors with apomorphine, N -n-propyl-norapomorphine or d -amphetamine reduced DOPA formation in the CN and SN to the same extent. Vice versa, both inhibition of DA receptors with haloperidol or (-)sulpiride and depletion of DA concentration with reserpine enhanced DOPA formation to a greater extent in the CN than in the SN. Apomorphine antagonized not only the effect of haloperidol and (-)sulpiride, but also, and even more effectively, that of reserpine. The results indicate that DA synthesis in the SN is controlled by both end-product inhibition and DA receptor-mediated mechanisms.     

The physiological significance of photosystem II heterogeneity in chloroplasts

Photosystem II in green plant chloroplasts displays heterogeneity both in the composition of its light-harvesting antenna and in the ability to reduce the plastoquinone pool. These two features are discussed in terms of chloroplast development and in view of a proposed photosystem II repair cycle.     

Haloperidol increases DOPAC in the substantia nigra but not in the ventral tegmental area

Haloperidol (0.1 to 0.5 mg/kg) caused a dose related increase in DOPAC content both in the substantia nigra (pars compacta + pars reticulata) (by 27 to 134%) and in the caudate nucleus (by 127 to 252%). On the contrary even 5 mg/kg of haloperidol failed to modify DOPAC level in the ventral tegmental area. The results indicate that DA cells in ventral tegmental area differ from those in the substantia nigra not only on anatomical grounds but also on a functional point of view.