Different feeding behaviours in a single predatory mite species. 2. Responses of two populations of Phytoseiulus longipes (Acari: Phytoseiidae) to various prey species,prey stages and plant substrates

Tritrophic studies involving several populations of the predatory mite Phytoseiulus longipes showed distinct life history traits depending on the prey offered and/or the plant substrate. In order to better understand the biology of this predator, the response to several combinations of prey species (Tetranychus evansi and Tetranychus urticae), prey stages (eggs and mobile stages) and plant substrates (bean and tomato leaf discs) has been assessed for two populations of P. longipes. Unlike what was found for life history traits, both populations displayed similar behaviour: they went and stayed more on tomato than on bean, they preferred T. urticae over T. evansi and mobile stages over eggs. Combining the previous life history data with the present results suggests that P. longipes may display host-plant mediated specialization on a prey species, T. evansi. Possible underlying mechanisms are discussed, as well as directions for future work.     

Estimation of Monod model parameters by hybrid differential evolution

A hybrid method based on evolutionary algorithms is developed in this study. Two additional operations, an acceleration operation and a migration operation, are embedded into the original version of differential evolution. These two operations are used for the improvement of the convergence speed without decreasing the diversity among the individuals. The acceleration operation is used to speed up convergence. However, the migration operation is used to increase the diversity among the individuals. The hybrid method is applied to estimate the parameters of the Monod model of a recombinant fermentation process. The model profiles based on ᇆ% variations of the initial concentrations of glucose can fit the experimental observations satisfactorily.     

Selection of peptide inhibitors for double-stranded RNA-dependent protein kinase PKR

Protein kinase inhibitors have been developed and applied as antitumor drugs. The majority of these inhibitors are derived from ATP analogs with limited specificity towards the kinase target. Here we present our proof-of-principle study on peptide inhibitors for kinases. Two peptides were selected by phage display against double-stranded RNA-dependent protein kinase (PKR). In vitro assay revealed that these peptides exhibit an inhibitory effect on PKR-catalyzed phosphorylation of the alpha subunit of eukaryotic initiation factor 2 (eIF2α). The peptides also interrupt PKR activity in cells infected by viruses, as PKR activation is one of the hallmarks of host response to viral infection. Kinetic study revealed that one of the peptides, named P1, is a competitive inhibitor for PKR, while the other, named P2, exhibits a more complicated pattern of inhibition on PKR activity. Fragment-based docking of the PKR-peptide complex suggests that P1 occupies the substrate pocket of PKR and thus inhibits the binding between PKR and eIF2α, whereas P2 sits near the substrate pocket. The computational model of PKR-peptide complex agrees with their kinetic behavior. We surmise that peptide inhibitors for kinases have higher specificity than ATP analogs, and that they provide promising leads for the optimization of kinase inhibitors.     

Identification of light and dark hypertrophic chondrocytes in mouse and rat chondrocyte pellet cultures

Hypertrophic “light” and “dark” chondrocytes have been reported as morphologically distinct cell types in growth cartilage during endochondral ossification in many species, but functional differences between the two cell types have not been described. The aim of the current study was to develop a pellet culture system using chondrocytes isolated from epiphyseal cartilage of neonatal mice and rats, for the study of functional differences between these two cell types. Hypertrophic chondrocytes resembling those described in vivo were observed by light and electron microscopy in sections of pellets treated with triiodothyronine, 1% fetal calf or mouse serum, 10% fetal calf serum or 1.7 MPa centrifugal pressure at day 14, and in pellets cultured with insulin or 0.1% fetal calf or mouse serum at day 21. A mixed population of light and dark chondrocytes was found in all conditions leading to induction of chondrocyte hypertrophy. This rodent culture system allows the differentiation of light and dark chondrocytes under various conditions in vitro and will be useful for future studies on tissue engineering and mechanisms of chondrocyte hypertrophy.     

The distribution of the most favorable temperatures for citrus flower induction in Israel

In this study the distribution of optimum temperatures for the induction of citrus blossoms in Israel has been determined. The number of flowers that form on citrus plants grown in the subtropics is known to be affected by the temperatures to which the plants are exposed. However, too few records of hourly temperatures exist in Israel to make an estimate of the occurrence and/or distribution of temperatures beneficial for citrus flower induction, although maximum and minimum temperatures are widely recorded. Thus, a model derived from the hourly records could be applied to the stations recording only maximum and minimum temperatures. The average optimum temperature was mapped for citrus flower induction throughout Israel.     

Norepinephrine: Adenosinetriphosphate ratios in purified adrenergic vesicles

Norepinephrine (NE):adenosinetriphosphate (ATP) ratios were studied in a highly purified fraction of large dense core vesicles isolated from the bovine splenic nerve. Vesicles prepared from nerves chilled ～10 and 30 min post mortem were compared. The NE:ATP molar ratio decreased from 6.3 to 4.8, p < 0.005; NE decreased from 61 to 42 nmol, while ATP decreased only from 9.6 to 8.8 nmol/mg protein. Animals weighing 180-360 kg were compared with heavier ones weighing 400-700 kg. NE increased from 42 to 68 nmol and ATP increased from 5.9 to 13.2 nmol/mg protein, while the NE:ATP molar ratio decreased from 7.2 to 5.2, p < 0.005. Changes during vesicle maturation were studied by comparing vesicles identically prepared from equal weights of a proximal nerve segment close to the coeliac ganglion and a distal, intrasplenic segment. NE increased from 45 to 70 nmol while ATP remained unchanged at 10.0 nmol/mg protein and the NE:ATP molar ratio increased from 4.5 to 7.0, p < 0.005. It was interpreted that vesicle ATP content, like dopamine β-hydroxylase, was established early in the cell body and remained unchanged during axoplasmic transport. ATP was in a complex which was relatively stable to post mortem hydrolysis at least between 10 and 30 min prior to chilling the nerves. The addition of newly synthesized NE into a readily releasable pool during axoplasmic transport occurs without ATP and can account for the increased ratio above 4:1 in the distal segment vesicles.     

Status and restoration of peatlands in northern Europe

Environmental management of peatlands,landscape ecology and protection of keybiotopes have created needs and pressure torestore drained peatlands to natural mireecosystems. Here, we summarize differentapproaches and restoration techniquesdeveloped for peatland management inEstonia, Sweden, and Finland wherepeatlands are abundant. Without rewetting,plant colonisation on abandoned cut-awayareas is slow due to harsh hydrological andmicroclimatic conditions. However, after restoration, cut-away peatlands may returnto a functional state close to that ofpristine mires, and therefore restore a netcarbon sink function within a few years. Inaddition, restoration techniques can helpto create buffer zones between terrestrialand limnic ecosystems that reduces thenutrient loading imposed on watercourses byforestry operations. Restoration may alsobe important for peatland conservationprograms as drained peatlands are part ofpresent and future conservation areas.Finally, restoration actions in themselvescan have negative environmental impacts.For instance, inundation of peat surfacesresulting from the rewetting process oftenincreases phosphorus leaching. Efforts onpeatland restoration should focus onenvironmental monitoring, research onrestoration and its environmental impact aswell as public relations activities. Inthat respect, knowledge transfer betweenacademics and managers should generatesynergy benefits.