Chemically induced gelation of polysaccharide produced by Methylobacterium organophilum

Both attractive and repulsive interactions between entangled Methylan chains were investigated with divalent cations that might form a salt bridge or generate an electrostatic attraction between the negatively charged groups in Methylan chains. The chemically induced gelation produces a thermally reversible gel. The gel strength was proportional to Methylan concentration in range from 1 to 5 g/l and was controlled by both Methylan and salt concentrations. © Rapid Science Ltd. 1998     

Alteration of Golgi structure in senescent cells and its regulation by a G protein γ subunit

Cellular senescence is a process wherein proliferating cells undergo permanent cell cycle arrest while remaining viable. Senescence results in enhanced secretion of proteins that promote cancer and inflammation. We report here that the structure of the Golgi complex which regulates secretion is altered in senescent cells. In cells where senescence is achieved by replicative exhaustion or in cells wherein senescence has been induced with BrdU treatment dependent stress, the Golgi complex is dispersed. The expression of a G protein γ subunit, γ11, capable of translocation from the plasma membrane to the Golgi complex on receptor activation increases with senescence. Knockdown of γ11 or overexpression of a dominant negative γ3 subunit inhibits Golgi dispersal induced by senescence. Overall these results suggest that in cellular senescence an upregulated G protein gamma subunit mediates alterations in the structure of the Golgi.     

Evaluation of Resistance Pattern to Fenpyroximate and Pyridaben in Tetranychus Urticae collected from Ggreenhouses and Apple Orchards using Lethal Concentration-slope Relationship

This study aimed to monitor the present and future developments of the resistance of Tetranychus urticae Koch to fenpyroximate and pyridaben, using the relationship of the LC₅₀ and slope of the concentration-mortality line in a probit model, for the provision of reliable resistance management tactics. Tetranychus urticae populations were collected from 16 commercial greenhouses, where various crops were cultivated, as well as from 10 apple orchards throughout Korea. The resistance to fenpyroximate and pyridaben of each population was estimated by calculating the median lethal concentration (LC₅₀), resistance ratio (RR) and slope of the concentration-mortality regression. Most of the greenhouse populations exhibited moderate levels of resistance, whereas the apple orchard populations showed only low levels, indicating that T. urticae populations in greenhouses were more strongly selected than those in apple orchards. Four population groups were established based on either the habitats (greenhouse and apple orchard) or acaricides (fenpyroximate and pyridaben). To test the hypothesis, “the slope is greatest at low and high levels of resistance,” the slopes were regressed as a function of the LC₅₀, and fitted to a polynomial regression. The polynomial regression model explained this relationship well for the four population groups (p < 0.05), indicating that the development of resistance toward fenpyroximate or pyridaben was consistent with the gradient. A laboratory selection study agreed with the results from both acaricide field populations. These results suggest that the gradient was a good indicator of the susceptibility of T. urticae to genetic variations, which was related to the LC₅₀. The application of these findings is also discussed in relation to the resistance management of T. urticae.     

Prolonged rapamycin treatment inhibits mTORC2 assembly and Akt/PKB

The drug rapamycin has important uses in oncology, cardiology, and transplantation medicine, but its clinically relevant molecular effects are not understood. When bound to FKBP12, rapamycin interacts with and inhibits the kinase activity of a multiprotein complex composed of mTOR, mLST8, and raptor (mTORC1). The distinct complex of mTOR, mLST8, and rictor (mTORC2) does not interact with FKBP12-rapamycin and is not thought to be rapamycin sensitive. mTORC2 phosphorylates and activates Akt/PKB, a key regulator of cell survival. Here we show that rapamycin inhibits the assembly of mTORC2 and that, in many cell types, prolonged rapamycin treatment reduces the levels of mTORC2 below those needed to maintain Akt/PKB signaling. The proapoptotic and antitumor effects of rapamycin are suppressed in cells expressing an Akt/PKB mutant that is rapamycin resistant. Our work describes an unforeseen mechanism of action for rapamycin that suggests it can be used to inhibit Akt/PKB in certain cell types.     

Potential application of antibody-mimicking peptides identified by phage display in immuno-magnetic separation of an antigen

Phage display was performed against human IgG (hIgG) through five rounds of 'biopanning'. Each round consisted of: (1) incubating a library of phage-displayed 12-mer peptides sequences on hIgG-coated magnetic beads, (2) washing the unbound phages, and (3) eluting the bound phages. The eluted phages were either amplified to enrich the pool of positive clones or subjected to the next round without amplification. Through ELISA, four clones (F9, D1, G5, and A10) showing specific binding affinity to hIgG were identified. Among these, F9 had the highest affinity (K(d)=6.2nM), only one order of magnitude lower than the native anti-hIgG antibody (0.66nM). Following the DNA sequences of the selected clones, four 12-mer peptides were chemically synthesized. Among them, D1 peptide showed the highest binding affinity to hIgG via SPR biosensor measurements. This peptide was conjugated to biofunctionalized magnetic beads, and its immuno-binding ability was compared with that of the native antibody immobilized to magnetic beads. The mol-to-mol binding efficacy of the peptide-coated magnetic beads was approximately 1000-fold lower than that of the antibody-coated magnetic beads. Our results suggest a feasibility of using antibody-mimicking peptides identified by phage display technique for immuno-magnetic separation of an antigen.     

Detecting and cleaning outliers for robust estimation of variogram models in insect count data

Outlier detection and cleaning procedures were evaluated to estimate mathematical restricted variogram models with discrete insect population count data. Because variogram modeling is significantly affected by outliers, methods to detect and clean outliers from data sets are critical for proper variogram modeling. In this study, we examined spatial data in the form of discrete measurements of insect counts on a rectangular grid. Two well-known insect pest population data were analyzed; one data set was the western flower thrips, Frankliniella occidentalis (Pergande) on greenhouse cucumbers and the other was the greenhouse whitefly, Trialeurodes vaporariorum (Westwood) on greenhouse cherry tomatoes. A spatial additive outlier model was constructed to detect outliers in both the isolated and patchy spatial distributions of outliers, and the outliers were cleaned with the neighboring median cleaner. To analyze the effect of outliers, we compared the relative nugget effects of data cleaned of outliers and data still containing outliers after transformation. In addition, the correlation coefficients between the actual and predicted values were compared using the leave-one-out cross-validation method with data cleaned of outliers and non-cleaned data after unbiased back transformation. The outlier detection and cleaning procedure improved geostatistical analysis, particularly by reducing the nugget effect, which greatly impacts the prediction variance of kriging. Consequently, the outlier detection and cleaning procedures used here improved the results of geostatistical analysis with highly skewed and extremely fluctuating data, such as insect counts.     

Phenology simulation model of Scotinophara lurida (Hemiptera: Pentatomidae)

A phenology simulation model was developed for Scotinophara lurida (Burmeister). The components for the model were a degree-day immigration flight model of overwintered adults, temperature-dependent developmental models of each stage, survival rates of each stage, and an adult oviposition model. A degree-day model for immigration flight of overwintered adults was developed with blacklight trap catch data by a Weibull function. Laboratory experiments using seven constant temperature regimens were conducted to determine the effect of temperature on the development of immature stages. Developmental rates of each immature stage fit well to a linear model. Distribution of developmental time for each immature stage was successfully modeled against physiological age by a Weibull function. To determine the temperature effect on longevity, fecundity, and survival of female adults, laboratory and greenhouse experiments were conducted. The adult developmental rate (1/median longevity) was described by a linear model. The oviposition model was developed incorporating the three components of average total fecundity, cumulative oviposition rate function, and survival rate function. The simulation model predicted the time of peak occurrences of life stages of S. lurida well.     

Functional response of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) to Aphis gossypii Glover (Homoptera: Aphididae) in the Laboratory

Stage specific functional response of Harmonia axyridis (Pallas) to varying densities of Aphis gossypii Glover was examined in a simplified cucumber leaf arena under laboratory conditions. All stages of H. axyridis were isolated individually for 24 h with different prey densities at 25 °C and a photoperiod of 16:8 (L:D) h. The number of prey consumed by the predator was checked at 3, 6, 12, and 24 h. All stages of H. axyridis showed a Type II functional response. Based on the random predator equation, estimated attack rates of H. axyridis at 24 h were 0.0037, 0.0442, 0.3590, 0.3228, and 0.1456, and estimated handling times were 4.1001, 2.4575, 0.7500, 0.2132, and 0.1708 h for the first, second, third, and fourth instars, and female adult, respectively.