Responses of Lipolexis oregmae (Hymenoptera: Aphidiidae) to different instars of Toxoptera citricida (Homoptera: Aphididae)

The effects of host instar of Toxoptera citricida Kirkaldy (Homoptera: Aphididae) on the performance of the parasitoid Lipolexis oregmae (Gahan) (Hymenoptera: Aphidiidae), originally Lipolexis scutellaris Mackauer, were evaluated in an effort to increase basic knowledge of this host-parasitoid association, improve field sampling methods, and potentially predict the success of parasitism in the field. L. oregmae was able to oviposit and develop in all four instars of T. citricida; however, there are differences in the quality of different host instars. Although second-instar hosts produce more L. oregmae progeny and a higher female-biased sex ratio, fourth-instar hosts produce L. oregmae progeny that are larger and have a higher realized fecundity. However, fourth-instar hosts require a longer handling time and expose the parasitoid female to more aphid behavioral defenses than do second-instar hosts. Additionally, results suggest that fourth-instar hosts may elicit a physiological immune response to parasitism; when aphids were observed being stung once, the number of L. oregmae larvae present on dissection after 4 d and the number of eclosed adults was lower in fourth- than in second-instar hosts. Pupal mortality of L. oregmae was also higher in fourth-instar hosts compared with second-instar hosts. The results of this study confirm that L. oregmae has a high reproductive rate and low incidence of incomplete parasitization on this host and is one of only a few natural enemies able to complete development in all instars of the brown citrus aphid in Florida.     

Structural approach of the mechanism of inhibition of alpha-chymotrypsin by coumarins

A pharmacophore associated to the inhibiton of alpha-chymotrypsin has been built based on the structural and electronic characterization of a series of coumarin derivatives.     

Mass measurements of C-terminally truncated alpha-crystallins from two-dimensional gels identify Lp82 as a major endopeptidase in rat lens

Molecular chaperone activity of lens alpha-crystallins is reduced by loss of the C terminus. The purpose of this experiment was to 1) determine the cleavage sites produced in vitro by ubiquitous m-calpain and lens-specific Lp82 on alpha-crystallins, 2) identify alpha-crystallin cleavage sites produced in vivo during maturation and cataract formation in rat lens, and 3) estimate the relative activities of Lp82 and m-calpain by appearance of protease-specific cleavage products in vivo. Total soluble protein from young rat lens was incubated with recombinant m-calpain or Lp82 and 2 mM Ca2+. Resulting fragmented alpha-crystallins were separated by two-dimensional gel electrophoresis. Eluted alpha-crystallin spots were analyzed by mass spectrometry. Cleavage sites on insoluble alpha-crystallins were determined similarly in mature rat lens nucleus and in cataractous rat lens nucleus induced by selenite. In vitro proteolysis of alphaA-crystallin by Lp82 and m-calpain produced unique cleavage sites by removing 5 and 11 residues, respectively, from the C terminus. In vivo, the protease-specific truncations removing 5 and 11 residues from alphaA were both found in maturing lens, whereas only the truncation removing 5 residues was found in cataractous lens. Other truncation sites, common to both calpain isoforms, resulted from the removal of 8, 10, 16, 17, and 22 residues from the C terminus of alphaA. Using uniquely truncated alphaA-crystallins as in vivo markers, Lp82 and m-calpain were both found to be active during normal maturation of rat lens, whereas Lp82 seemed especially active during selenite cataract formation. These C-terminal truncations decrease chaperone activity of alpha-crystallins, possibly leading to the observed increases in insoluble proteins during aging and cataract. The methodology that allowed accurate mass measurements of proteins eluted from 2D gels should be useful to examine rapidly other post-translational modifications.     

Förster resonance energy transfer measurements are consistent with a helical bundle model for lipid-free apolipoprotein A-I

Apolipoprotein (apo) A-I mutants were constructed for FRET studies to distinguish between two possible lipid-free conformers, a globular helix bundle and an elongated helical hairpin. Mutants containing a single Trp at position 50 were prepared by replacing Trps at positions 8, 72, and 108 with Phe (W@50). Two mutants were constructed from W@50 by incorporating Cys at Arg83 (W@50R83C) or Arg173 (W@50R173C) for attachment of the fluorescent probe AEDANS. Secondary structure of the mutants is very similar to wild type (wt) apo A-I, and fluorescence emission indicates that W50 is protected from solvent. Thermal stabilities of the AEDANS-labeled mutants are also similar to wt. These results indicate that no discernible changes occur in structure or stability as a result of mutations or labeling. The FRET data from W@50 to AEDANS are well-represented by a single distance distribution function with a distance of approximately 22 A for W@50R83C and approximately 19 A for W@50R173C. These distances are consistent with theoretical values calculated from a helical bundle model but not from a helical hairpin. A probability distance distribution function yields significantly small half-width values of 5.6 and 3.7 A, respectively, suggesting low conformational dynamics in both mutants. Differential scanning calorimetry (DSC) was performed on wt and a C-terminal deletion mutant, Delta(187-243), to obtain information on domain architecture. Contrary to expectations, both proteins unfold cooperatively. The results are consistent with the presence of a single folded domain within residues 1-186. These results support the presence of a discrete globular bundle conformation for lipid-free apo A-I.     

Modern chironomids (Diptera: Chironomidae) and the environmental variables that influence their distribution in the Araucanian lakes,south-central Chile

Hydrobiologia - Detailed studies of Chironomidae fauna can yield a reliable tool to evaluate the effects of climatic change and anthropogenic disturbances over freshwater ecosystems. Using modern...     

Fatty Acid Acylation of Rat Brain Myelin Proteolipid Protein In Vitro: Identification of the Lipid Donor

The immediate acyl chain donor for fatty acid esterification of proteolipid protein (PLP) was identified in an in vitro system. Rat brain total membranes, after removal of crude nuclear and mitochondrial fractions, were incubated with radioactive acyl donors, extracted with chloroform/methanol, and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In the presence of [3H]palmitic acid, CoA, ATP, and Mg2+, acylation of endogenous PLP occurred at a linear rate for at least 2 h. The radioactivity was associated with the protein via an ester linkage, mainly as palmitic acid. Omission of ATP, CoA, Mg2+, or all three reduced fatty acid incorporation into PLP to 44, 27, 8, and 4%, respectively, of the values in the complete system. Incubation of the membrane fraction with [3H]palmitoyl-CoA in the absence of CoA and ATP led to highly labeled PLP. These data demonstrate that activation of free fatty acid is required for acylation. Phospholipids and glycolipids were not able to acylate the PLP directly. Finally, when isolated myelin was incubated with [3H]palmitoyl-CoA in the absence of cofactors, only PLP was labeled, thus confirming the identity of palmitoyl-CoA as the direct acyl chain donor and suggesting that the acylating activity and the PLP pool available for acylation are both in the myelin.     

Portable microsatellite primers for Ficus (Moraceae)

? Premise of the study: Highly portable microsatellite primers were developed for Ficus to facilitate investigation of genetic structure of complete regional floras using a single set of markers. ? Methods and Results: Pyrosequencing of five species of Ficus produced a library of 5723 potential primers. Potential primers found in at least two species and presenting identical annealing temperatures were tested on a set of five additional Ficus species. A set of 20 primer pairs producing well-defined and easily readable peaks was retained and tests showed their potential utility for analyzing population genetic structure of 24 Ficus species from Taiwan. Numbers of alleles per locus ranged from one to six in the least variable species and from one to 17 in the most variable species. ? Conclusions: The results indicate that our set of primers can be used to analyze polymorphism and compare levels of polymorphism among Ficus species.