Complete profiling of some eicosanoids using glass capillary gas chromatography with flame ionization detection: application to biological samples

The improvement of glass capillary preparation technology has allowed the development of high-resolution and very low-bleeding gas chromatographic columns. Using an all-glass injector and a flame ionization detector, it was possible to get a complete resolution of some of the principal stable oxygenated metabolites of arachidonic acid (cyclized and aliphatic, i.e., eicosanoids). Due to the low bleeding of the column, detector limits exceed those obtained with previously prepared columns. Total profiling studies have been obtained with small amounts of activated washed platelets after only an ether extraction, allowing for the first time a complete, simultaneous survey of cycloxygenase and lipoxygenase pathways. The application has been extended with success to other cell types.     

Nuclear envelope‐associated dynein drives prophase centrosome separation and enables Eg5‐independent bipolar spindle formation

The microtubule motor protein kinesin‐5 (Eg5) provides an outward force on centrosomes, which drives bipolar spindle assembly. Acute inhibition of Eg5 blocks centrosome separation and causes mitotic arrest in human cells, making Eg5 an attractive target for anti‐cancer therapy. Using in vitro directed evolution, we show that human cells treated with Eg5 inhibitors can rapidly acquire the ability to divide in the complete absence of Eg5 activity. We have used these Eg5‐independent cells to study alternative mechanisms of centrosome separation. We uncovered a pathway involving nuclear envelope (NE)‐associated dynein that drives centrosome separation in prophase. This NE‐dynein pathway is essential for bipolar spindle assembly in the absence of Eg5, but also functions in the presence of full Eg5 activity, where it pulls individual centrosomes along the NE and acts in concert with Eg5‐dependent outward pushing forces to coordinate prophase centrosome separation. Together, these results reveal how the forces are produced to drive prophase centrosome separation and identify a novel mechanism of resistance to kinesin‐5 inhibitors.     

A physiological analogy of the niche for projecting the potential distribution of plants

Aim  To develop a physiologically based model of the plant niche for use in species distribution modelling. Location  Europe. Methods  We link the Thornley transport resistance (TTR) model with functions which describe how the TTR’s model parameters are influenced by abiotic environmental factors. The TTR model considers how carbon and nutrient uptake, and the allocation of these assimilates, influence growth. We use indirect statistical methods to estimate the model parameters from a high resolution data set on tree distribution for 22 European tree species. Results  We infer, from distribution data and abiotic forcing data, the physiological niche dimensions of 22 European tree species. We found that the model fits were reasonable (AUC: 0.79–0.964). The projected distributions were characterized by a false positive rate of 0.19 and a false negative rate 0.12. The fitted models are used to generate projections of the environmental factors that limit the range boundaries of the study species. Main conclusions  We show that physiological models can be used to derive physiological niche dimensions from species distribution data. Future work should focus on including prior information on physiological rates into the parameter estimation process. Application of the TTR model to species distribution modelling suggests new avenues for establishing explicit links between distribution and physiology, and for generating hypotheses about how ecophysiological processes influence the distribution of plants.     

An Aphid-Secreted Salivary Protease Activates Plant Defense in Phloem

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T-independent but not T-dependent antigens maintain surface Ig of lymphocytes.

The effect of T-independent (TIA) and T-dependent (IDA) antigens on the surface Ig of 24-hr cultured rabbit spleen cells was investigated by two techniques: the proportion of cells bearing surface Ig was determined by direct rosette formation with anti-light chain allotype-coated erythrocytes; the total amount of surface Ig was estimated by labeling the cells with anti-allotype ¹²⁵I-labeled Fab fragments. The addition of TIA resulted in the maintenance of the proportion of Ig-bearing cells almost to the initial level, an effect which could not be obtained with any of the TDA tested. The same type of effect was observed when the total amount of surface Ig was measured, i.e., there was a slight reduction (about 24%) in the amount of surface Ig in cultures to which TIAs were added and an almost sixfold reduction (about 70%) in cultures to which TDA, Con A, or no antigen was added. Some but not all of the TIA were able to induce [³H]TdR incorporation in 3-day spleen-cell cultures. We concluded that the common feature of TIA is the ability to stimulate the turnover of B-cell surface Ig, a feature that can be used for an easy screening of TIA.     

Fine mapping of the chicken salmonellosis resistance locus (SAL1)

Salmonella enterica serovar Typhimurium is a Gram-negative bacterium that has a significant impact on both human and animal health. It is one of the most common food-borne pathogens responsible for a self-limiting gastroenteritis in humans and a similar disease in pigs, cattle and chickens. In contrast, intravenous challenge with S. Typhimurium provides a valuable model for systemic infection, often causing a typhoid-like infection, with bacterial replication resulting in the destruction of the spleen and liver of infected animals. Resistance to systemic salmonellosis in chickens is partly genetically determined, with bacterial numbers at systemic sites in resistant lines being up to 1000-fold fewer than in susceptible lines. Identification of genes contributing to disease resistance will enable genetic selection of resistant lines that will reduce Salmonella levels in poultry flocks. We previously identified a novel resistance locus on Chromosome 5, designated SAL1 . Through the availability of high-density SNP panels in the chicken, combined with advanced back-crossing of the resistant and susceptible lines, we sought to refine the SAL1 locus and identify potential positional candidate genes. Using a 6^th generation backcross mapping population, we have confirmed and refined the SAL1 locus as lying between 54.0 and 54.8 Mb on the long arm of Chromosome 5 ( F  = 8.72, P  = 0.00475). This region spans 14 genes, including two very striking functional candidates; CD27-binding protein ( Siva ) and the RAC -alpha serine/threonine protein kinase homolog , AKT1 ( protein kinase B , PKB ).     

EXPERIMENTAL EVOLUTION OF RESISTANCE IN BRASSICA RAPA: CORRELATED RESPONSE OF TOLERANCE IN LINES SELECTED FOR GLUCOSINOLATE CONTENT

The evolutionary response of plant populations to selection for increased defense may be constrained by costs of defense. The purpose of this study was to investigate such constraints on the evolution of defense due to a cost of defense manifested as a trade-off between defense and tolerance. Variation in the response to artificial damage (tolerance) among lines of Brassica rapa that had been artificially selected for foliar glucosinolate content (defense) was examined. Leaf area was removed from replicates of three selection lines (high glucosinolates, control, and low glucosinolates) at three damage levels (0%, 20%, and 60% damage). An external cost of defense would result in a statistically significant selection line by damage treatment interaction, with those selected for high defense expressing less tolerance than those selected for low defense. Damage treatment had a significant overall effect on estimated total fitness, with fitness declining with increasing damage level. Further, selection line also had a significant overall effect on estimated total fitness, with low-defense selection lines having higher fitness compared to both control and high-defense selection lines. More importantly, a cost of defense in terms of tolerance was demonstrated by a significant selection line-by-damage treatment interaction. This interaction was in the direction to demonstrate a genetic trade-off between defense and tolerance, with low-defense selection lines decreasing estimated total fitness in response to damage less than both control and high-defense selection lines. Variation in tolerance among selection lines was due to the greater ability of low-defense lines to maintain fruit and seed production despite the presence of damage. In terms of tolerance, this cost of glucosinolate production in B. rapa could constrain the evolution of increased defense and, in so doing, maintain individuals within the population that are poorly defended yet tolerant.     

Cell degeneration during early development of hymenopteran olfactory sensilla

The imaginal pore plates of Hymenoptera apocrita so far examined embody five or six envelope cells respectively. In early developmental stages, however, supernumerary envelope cells have been found. The results are discussed in the context of cell death as a developmental phenomenon.     

Protein arginine methylation promotes therapeutic resistance in human pancreatic cancer

Pancreatic cancer is a lethal disease with limited treatment options for cure. A high degree of intrinsic and acquired therapeutic resistance may result from cellular alterations in genes and proteins involved in drug transportation and metabolism, or from the influences of cancer microenvironment. Mechanistic basis for therapeutic resistance remains unclear and should profoundly impact our ability to understand pancreatic cancer pathogenesis and its effective clinical management. Recent evidences have indicated the importance of epigenetic changes in pancreatic cancer, including posttranslational modifications of proteins. We will review new knowledge on protein arginine methylation and its consequential contribution to therapeutic resistance of pancreatic cancer, underlying molecular mechanism, and clinical application of potential strategies of its reversal.