Biochemical and populational responses of an aquatic bioindicator species,Daphnia longispina,to a commercial formulation of a herbicide (Primextra® Gold TZ) and its active ingredient (S-metolachlor)

The growing demand of human populations for food supplies has led to an increase in the use of synthetic products, mainly pesticides, which induce adverse effects not only to target organisms, but also to non-target biota of agroecosystems. Aquatic ecosystems in the proximity of agricultural areas are particularly vulnerable to pesticides, which cause underperformance or extinction of non-target sensitive species. Once in the aquatic system, these chemicals can affect biological processes at multiple levels (molecular, individual, populational), causing ecosystem imbalance across multiple scales. In this study, the effect of a commercial formulation of a herbicide (Primextra® Gold TZ) and its main active ingredient (a.i., S-metolachlor) was studied on a freshwater cladoceran species (Daphnia longispina), at different levels of biological organization and temporal scales. S-metolachlor is used in many herbicide formulations applied in corn/maize cultures, which is a relevant culture worldwide. As a first step, the acute and chronic effects of both commercial formulation and a.i. were quantified, and both formulations negatively affected the cladoceran's survival and reproductive parameters (age at first reproduction, number of offspring and number of broods), as well as the population's rate of increase. Whilst acute effects were comparable, the commercial formulation was slightly more toxic (EC₅₀ was two-times lower) than the a.i. in chronic exposures, being prejudicial to D. longispina populations above 4.0 mg/L of S-metolachlor. In a second experimental step, we focused on the potential multi-generational impacts of the exposure to the a.i. alone on biochemical (lipid biomarkers, namely fatty acids) and populational responses, because of the relevance of S-metolachlor as a biosynthesis inhibitor in many herbicidal formulations. The herbicide caused a significant decrease in Daphnia fecundity (in the size of the 1st clutch), but no concomitant alterations were found in fatty acid profiles of mothers or offspring. More important, this experiment showed that S-metolachlor did not cause effects in the subsequent generation, thus suggesting that biotic communities may recover after exposure to the xenobiotic.     

The control of flower initiation by gibberellin in Helianthus annuus L. (sunflower), a non-photoperiodic plant

The involvement of gibberellins in the control of flowering of sunflower was studied by direct application of GA₃ to the apex of the plants, analysis of the endogenous levels of gibberellin-like substances at different plant ages, and indirectly by the application of paclobutrazol, an inhibitor of gibberellin synthesis. GA₃ speeded-up flower initiation and floral apex development. The time of GA₃ application was more critical than the amount of GA₃ applied. The endogenous levels of gibberellin-like compounds increased significantly by day 15 after sowing. The application of paclobutrazol markedly delayed floral initiation and this effect was also depedent on plant age. Both GA₃ and paclobutrazol had their greatest effects between 10 and 20 days after sowing suggesting that an increase in gibberellins in that time period plays a role in floral initiation.     

The evolution of primate communities and societies in Madagascar

During their 120 to 165 million years of isolation, the flora and fauna of Madagascar evolved, to a large extent, independently of the African mainland.¹ In contrast to other oceanic islands, Madagascar is large enough to house the major components of tropical ecosystems, allowing tests of evolutionary hypotheses on the level of complete communities. Taking lemurs, the primates of Madagascar, as an example, evolutionary hypotheses correctly predict the organization of their community structure with respect to ecological correlates. Lemur social systems and their morphological correlates, on the other hand, deviate in some respects from those of other primates. Apparently, lemur social systems are influenced by several selection pressures that are weak or rare in other primates. These include variable activity patterns and avoidance of infanticide. The interspecific variation in lemur social systems therefore offers a unique opportunity for a comprehensive study of the determinants of primate social systems.     

An improved approach to evaluate car sharing options

We develop an improved approach to evaluate car sharing options under uncertain environments with the combination of Fuzzy Analytic Hierarchy Process (F-AHP) and Fuzzy Technique for Order Preference by Similarity to Ideal Solution (F-TOPSIS), which consists of three steps. In the first step, we propose a SCUMN (Specific, Comprehensive, Understandable, Measurable, and Neutral) methodology to identify appropriate indicators and obtain a final list of 24 indicators according to their relevance to car sharing options. In the second step, we determine the weight of each indicator with F-AHP and conduct consistency check of the comparison matrix of selected indicators. In the third step, comparison of different options is performed with selected indicators and F-TOPSIS. A case study is provided to validate the proposed approach. Twenty-four indicators are identified to evaluate five different car sharing options and rank them according to their closeness coefficients in decreasing order. And thirty-one sensitivity analysis experiments are conducted to figure out the influence of indicators on decision making. The experimental results show that the proposed approach is capable of evaluating car sharing options with uncertainty and vagueness. F-AHP is able to determine the weight for each selected indicator and F-TOPSIS demonstrates its advantage in comparing potential options.     

Synthesis and in vitro antiproliferative evaluation of novel N-alkylated 6-isobutyl- and propyl pyrimidine derivatives

A series of novel N-alkylated C-6-isobutyl- or -propyl pyrimidine derivatives were synthesized and their antiproliferative effect was evaluated on a panel of tumor cell lines including leukemia cell line K562 and normal diploid human fibroblasts. N-methoxymethylated 5-methylpyrimidin-2,4-dione with di(benzyloxy)isobutyl at C-6 (14b) showed the strongest effect on the cell growth at micromolar concentrations. Mechanisms of action for the lipophilic compound 14b predicted in silico, pointed to its anticancer and antimetastatic potential exerted through inhibition of DNA or RNA polymerases and adhesion molecules. The latter mechanism has been supported in vitro for adherent tumor cell lines.     

The effects of neighbors on the growth and survival of shrub seedlings following fire

Where plant species vie for limited resources, disturbances might preclude competition by releasing a flush of nutrients, or by reducing biomass and thereby diminishing the consumption of resources. However, if new seedlings colonize in clumps, they may still deplete resources within the local aggregations, which may then reduce their growth and survivorship. We investigated competition among seedlings in a burned area by examining the relationship between the performance of newly established shrub seedlings of Ceanothus impressus and (1) the proximity and (2) the identity of their near neighbors. We also investigated the relationship between neighbor proximity and the availability of water. Both survivorship and growth of C. impressus were positively associated with increasing distance to near neighbors, in a manner consistent with resource competition. The availability of water (as determined by pre-dawn xylem pressure potentials) tended to be greater when neighbors were farther away, providing evidence that water was a resource for which plants were competing. This conclusion is reinforced by the finding that the effects of neighbors were stronger in drought years, suggesting that yearly variation in the availability of an important resource (water) can affect the strength of competitive interactions. This suggests that after disturbances, when some resources are apparently abundant on a large scale, competition may be important in determining the small scale patterns of seedling growth and survival.     

Measurement of 7-dehydrocholesterol and cholesterol in hair can be used in the diagnosis of Smith-Lemli-Opitz syndrome

7-dehydrocholesterol (7-DHC) and cholesterol (CHOL) are biomarkers of Smith-Lemli-Opitz Syndrome (SLOS), a congenital autosomal recessive disorder characterized by elevated 7-DHC level in patients. Hair samples have been shown to have great diagnostic and research value, which has long been neglected in the SLOS field. In this study, we sought to investigate the feasibility of using hair for SLOS diagnosis. In the presence of antioxidants (2,6-ditert-butyl-4-methylphenol and triphenylphosphine), hair samples were completely pulverized and extracted by micro-pulverized extraction in alkaline solution or in n-hexane. After microwave-assisted derivatization with N,O-Bis(trimethylsilyl)trifluoroacetamide, the analytes were measured by GC-MS. We found that the limits of determination for 7-DHC and CHOL were 10 ng/mg and 8 ng/mg, respectively. In addition, good linearity was obtained in the range of 50–4000 ng/mg and 30–6000 ng/mg for 7-DHC and CHOL, respectively, which fully meets the requirement for SLOS diagnosis and related research. Finally, by applying the proposed method to real hair samples collected from 14 healthy infants and two suspected SLOS patients, we confirmed the feasibility of hair analysis as a diagnostic tool for SLOS. In conclusion, we present an optimized and validated analytical method for the simultaneous determination of two SLOS biomarkers using human hair.     

Experiments with artificial nests provide evidence for ant community stratification and nest site limitation in a tropical forest

Ants are dominant in tropical forests and many species nest in hollow cavities. The manner in which species are vertically stratified in these complex habitats is not known, with lack of nest sites being proposed to limit ant populations. Here, we assess ant community stratification and nest site limitation in a lowland rainforest in New Guinea using experimental addition of artificial bamboo nests of two cavity sizes (small: ~12 mm large: ~32 mm diameter) placed at ground level, in the understorey, and in the canopy. We also conducted a pilot experiment to test the utility of nest translocation. Nests were checked for occupancy after 10 weeks and half of the occupied nests were then translocated between forest plots, while keeping same vertical position. Occupancy of small nests was much higher in the understorey and canopy than at ground level (~75% vs. ~25%). Translocation was successful, as a majority of nests was inhabited by the same species before and after translocation and there was no impact of translocation to a different plot compared to the control, except for a reduction in colony size at ground level. Our experiment demonstrates a vertical stratification in community composition of ants nesting in hollow dead cavities and shows that these ants are more nest site limited in the higher strata than at ground level. Use of small artificial cavities has great potential for future experimental studies, especially for those focused on arboreal ants, as occupancy is high and translocation does not negatively affect their colony size. Abstract in Tok Pisin is available with online material.