Pro-survival effects of JNK and p38 MAPK pathways in LPS-induced activation of BV-2 cells

Identifying MAPK pathways and understanding their role in microglial cells may be crucial for understanding the pathogenesis of neurodegenerative diseases since activated microglia could contribute to the progressive nature of neurodegeneration. In this study we show that the JNK pathway plays an important role in the survival of resting microglia BV-2 cells, as evidenced by Annexin-V positive staining and caspase-3 activation in cells treated with the specific JNK inhibitor SP600125. During LPS-induced activation of BV-2 cells inhibition of the p38 and JNK pathways with SB203580 and SP600125, respectively, results in apoptosis as detected by apoptotic markers. In the presence SP600125 the phosphorylation of p38 was significantly increased both in control and LPS-activated BV-2 cells. This suggests that the pro-survival role of JNK is possible due to its abrogation of a potentially apoptotic signal mediated by p38 MAPK pathway. Furthermore, inhibition of the p38 MAPK pathway during LPS-induced activation of BV-2 cells resulted in an increased phosphorylation of c-Jun, suggesting that the pro-survival effect of p38 MAPK during inflammatory conditions involves the JNK pathway. In conclusion, the results of this study demonstrate that both the JNK and p38 MAPK pathways possess anti-apoptotic functions in the microglial cell line BV-2 during LPS-induced activation.     

Quantitative analysis of photosynthetic carbon metabolism in protoplasts and intact leaves of barley. Determination of carbon fluxes and pool sizes of metabolites in different cellular compartments

Rates of carbon fluxes and pool sizes of photosynthetic metabolites in different cellular compartments of barley protoplasts were calculated from the time curves of their labeling in the medium of ¹⁴CO₂. Using membrane filtration procedure, kinetics of ¹⁴C incorporation into the products of steady-state photosynthesis was determined separately in chloroplasts, mitochondria and cytosol of barley protoplasts illuminated for different periods in the air containing ¹⁴CO₂. To extract the quantitative information, analytical labeling functions P(t) describing the dependence of ¹⁴C content in the primary, intermediate and end products of a linear reaction chain upon the duration of tracer feeding have been derived. The parameters of these functions represent pool sizes of metabolites and rates of carbon fluxes. The values of these parameters were determined by fitting the experimental labeling curves to the functions P(t) by means of non-linear regression procedure. To elucidate the possible effects of fractionation on the photosynthetic carbon metabolism, the parameters of protoplasts were compared with corresponding values in intact leaves of barley.     

Lack of between- and within-species isoenzyme variability in Aquila eagles (Aves: Accipitriformes)

Isoenzyme analysis is a fast and inexpensive method for taxonomic and population genetic analyses. Variation of eight enzymes and two non-specific blood proteins among five species of eagles in genus Aquila was analysed with the aim of detecting species-specific markers and intraspecies variation for population genetic studies. However, no isoenzyme variability was detected. We conclude that isoenzyme analysis of blood samples has limited value for taxonomic, population and hybridization studies among eagles.     

Dependence of phenotypic variance in body size on environmental quality

The recent "overhead threshold" model for optimal age and body size at maturity (Day and Rowe 2002 ) predicts that phenotypic variability in adult body size will be low under inferior environmental quality and will increase with improving conditions. The model is, however, based on a potentially restrictive assumption of a monotone increase of fecundity with increasing body size. On the basis of a numerical model, we show that introducing the concept of maximum adult body size changes the predictions of the model. The dependence of variability in adult body size on environmental quality becomes a concave function with a maximum at intermediate values. Depending on the range of environmental conditions considered, one may therefore expect to observe both increasing and decreasing functions. We test the predictions of our model on a literature-based database of 131 insect species covering all major orders. We demonstrate that, in most species, relative phenotypic variation in body size decreases when environment-specific average of adult body size increases. In the majority of cases at least, such a relationship can be interpreted as a decreased relative variation in better growing conditions. With some potentially meaningful exceptions (e.g., females of capital-breeding insects), the general pattern was largely invariable across different taxa, ecological subdivisions, and sexes.     

A cytosolic pathway for the conversion of hydroxypyruvate to glycerate during photorespiration in Arabidopsis

Deletion of any of the core enzymes of the photorespiratory cycle, one of the major pathways of plant primary metabolism, results in severe air-sensitivity of the respective mutants. The peroxisomal enzyme hydroxypyruvate reductase (HPR1) represents the only exception to this rule. This indicates the presence of extraperoxisomal reactions of photorespiratory hydroxypyruvate metabolism. We have identified a second hydroxypyruvate reductase, HPR2, and present genetic and biochemical evidence that the enzyme provides a cytosolic bypass to the photorespiratory core cycle in Arabidopsis thaliana. Deletion of HPR2 results in elevated levels of hydroxypyruvate and other metabolites in leaves. Photosynthetic gas exchange is slightly altered, especially under long-day conditions. Otherwise, the mutant closely resembles wild-type plants. The combined deletion of both HPR1 and HPR2, however, results in distinct air-sensitivity and a dramatic reduction in photosynthetic performance. These results suggest that photorespiratory metabolism is not confined to chloroplasts, peroxisomes, and mitochondria but also extends to the cytosol. The extent to which cytosolic reactions contribute to the operation of the photorespiratory cycle in varying natural environments is not yet known, but it might be dynamically regulated by the availability of NADH in the context of peroxisomal redox homeostasis.     

An experimental approach to the formation of diet preferences and individual specialisation in European mink

Individual dietary specialisation can occur within populations even when average diets suggest that the population has a generalist feeding strategy. Individual specialisation may impact fitness and has been related to demographic traits, ecological opportunity, competition, learning and animal personality. However, the causation and formation of individual specialisation are not fully understood. Experiments on animals raised in controlled environments provide an opportunity to examine dietary preferences and learning largely independent from variation in lifetime experiences and ecological opportunity. Here, we use a feeding experiment to examine individual specialisation and learning in captive bred European mink (Mustela lutreola) in an Estonian conservation programme. In a series of cafeteria experiments, animals could choose between one familiar food item (Baltic herring Clupea harengus membras) and two initially novel ones (noble crayfish Astacus astacus and house mouse Mus musculus). In general, mice were rarely eaten whilst crayfish consumption increased over time and fish decreased. At the individual level, there was a mix of generalists and crayfish or fish specialists, and the individuals differed in learning time in relation to novel prey. Our results indicate that individual variation in innate preferences and learning both contributes to individual diet specialisation. The differences in learning indicate individual variation in behavioural plasticity, which in turn can be related to personality. This could be of concern in conservation, as personality has been shown to affect survival in translocations.     

Maturation at a young age and small size of European smelt (<Emphasis Type="Italic">Osmerus eperlanus</Emphasis>): A consequence of population overexploitation or climate change?

Age of fish at maturation depends on the species and environmental factors but, in general, investment in growth is prioritized until the first sexual maturity, after which a considerable and increasing proportion of resources are used for reproduction. The present study summarizes for the first the key elements of the maturation of European smelt (Osmerus eperlanus) young of the year (YoY) in the North-eastern Gulf of Riga (the Baltic Sea). Prior to the changes in climatic conditions and collapse of smelt fishery in the 1990s in the Gulf of Riga, smelt attained sexual maturity at the age of 3–4 years. We found a substantial share (22%) of YoY smelt with maturing gonads after the collapse of the smelt fisheries. Maturing individuals had a significantly higher weight, length and condition factor than immature YOY, indicating the importance of individual growth rates in the maturation process. The proportion of maturing YoY individuals increased with fish size. We discuss the factors behind prioritizing reproduction overgrowth in early life and its implications for the smelt population dynamics.     

Cascading effects of variation in plant vigour on the relative performance of insect herbivores and their parasitoids

Abstract 1. Consequences of variation in food plant quality were estimated for a system consisting of two monophagous noctuid herbivores and three ichneumonid parasitoids.
2. In a natural population, pupal weights of the herbivores in this system, Nonagria typhae and Archanara sparganii , were found to be highly variable. Pupal weights increased strongly and consistently with the increase in the vigour of the host plant, Typha latifolia , providing support for the plant vigour hypothesis. Correspondingly, as the moths do not feed as adults, a strong, positive correlation between host vigour and fecundity of the herbivores would be expected.
3. There were strong and positive relationships between adult body sizes of the parasitoids and the sizes of their lepidopteran hosts. Moreover, a direct, positive link between plant quality and parasitoid size was documented.
4. For all three parasitoids, cascading effects of plant quality on body size were weaker than for the herbivores. Differences in the importance of adult feeding and oviposition behaviour suggest that dependence of fitness on body size is also weaker in the parasitoids than in the moths. It is therefore concluded that the numerical response of the herbivore population to a change in plant quality should exceed the corresponding response in the parasitoids.
5. The results of this work imply that variation in plant variables may affect performance of different trophic levels to a different extent. It is suggested that the importance of adult feeding for the reproductive success (capital vs. income breeding strategies) in both herbivores and parasitoids is an essential aspect to consider when predicting responses of such a system to changes in plant quality.     

Influence of mitochondrial genome rearrangement on cucumber leaf carbon and nitrogen metabolism

The MSC16 cucumber (Cucumis sativus L.) mitochondrial mutant was used to study the effect of mitochondrial dysfunction and disturbed subcellular redox state on leaf day/night carbon and nitrogen metabolism. We have shown that the mitochondrial dysfunction in MSC16 plants had no effect on photosynthetic CO₂ assimilation, but the concentration of soluble carbohydrates and starch was higher in leaves of MSC16 plants. Impaired mitochondrial respiratory chain activity was associated with the perturbation of mitochondrial TCA cycle manifested, e.g., by lowered decarboxylation rate. Mitochondrial dysfunction in MSC16 plants had different influence on leaf cell metabolism under dark or light conditions. In the dark, when the main mitochondrial function is the energy production, the altered activity of TCA cycle in mutated plants was connected with the accumulation of pyruvate and TCA cycle intermediates (citrate and 2-OG). In the light, when TCA activity is needed for synthesis of carbon skeletons required as the acceptors for NH₄ ⁺ assimilation, the concentration of pyruvate and TCA intermediates was tightly coupled with nitrate metabolism. Enhanced incorporation of ammonium group into amino acids structures in mutated plants has resulted in decreased concentration of organic acids and accumulation of Glu.