Post-release survey to assess impact and potential host range expansion by Amitus hesperidum and Encarsia perplexa, two parasitoids introduced for the biological control of the citrus blackfly, Aleurocanthus woglumi in Dominica

Four years after the release of two exotic parasitoids, Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) and Encarsia perplexa Huang and Polaszek (Hymenoptera: Aphelinidae) for the classical biological control of the citrus blackfly (CBF), Aleurocanthus woglumi Ashby (Hemiptera: Aleyrodidae) in Dominica, a survey was conducted to assess establishment as well as potential nontarget effects especially on Aleyrodidae and other related taxa. CBF populations were low to non-existent in 50 of 51 field sites examined. At the site where CBF was encountered, both E. perplexa and A. hesperidum were present and CBF populations were declining. The two parasitoids were not among the several species collected on nontarget Aleryodidae and Hemiptera. It is concluded that E. perplexa and A. hesperidum have kept CBF populations under effective biological control in Dominica and there is no evidence of any nontarget effects on other Aleyrodidae or their natural enemies. Handling Editor: Dirk Babendreier.     

DNA damage induced by phorbol ester-stimulated neutrophils is augmented by extracellular cofactors. Role of histidine and metals

Activated neutrophils cause extensive DNA damage in neighboring nonphagocytic cells. To determine whether compounds in the extracellular milieu participate in the DNA damage process, murine neutrophils were cocultivated with target tumor cells in media of varying composition. Using the alkaline elution assay, it was found that the level of strand breaks induced was significantly higher (2.8-fold) in complex cell culture media than in minimal phosphate-buffered saline. Addition of amino acids in general and of histidine in particular increased the level of damage nearly to that observed in complete media (2.7- and 2.1-fold, respectively). The histidine stimulation was concentration-dependent and reached a maximum at 100-400 microM. The mechanism whereby this occurred is not proven but probably derived from chelation of metals and participation in a site-specific Fenton reaction. Addition of the cell-impermeable chelator EDTA dramatically inhibited induction of strand breaks by neutrophils in complete media and prevented the enhancement of damage induced by histidine in phosphate-buffered saline. None of the effects on neutrophil-induced damage could be attributed to modulation of the oxidative burst activity of the cells (O2- and H2O2 production). Histidine also enhanced induction of strand breaks by reagent H2O2. However, EDTA had no effect or actually increased the level of damage induced by both a bolus of H2O2 and a flux of H2O2 generated by glucose oxidase. The cell-permeable chelator o-phenanthroline inhibited both neutrophil- and H2O2-induced damage. The results indicate that secondary reactions involving extracellular amino acids and metals contribute significantly to neutrophil-induced DNA damage to neighboring cells. Moreover, the data show that the mechanism whereby neutrophils induce this damage cannot be attributed solely to secretion of H2O2.     

Dynamics of fluorescence dequenching of ostrich-quenched fluorescein biotin: a multifunctional quantitative assay for biotin

We describe a simple and rapid quantitative assay for biotin and biotin conjugates. The assay is based on the kinetic analysis of the enhancement of fluorescence of streptavidin/fluorescein biotin complexes in the presence of biotin. The kinetic response of fluorescence enhancement is proportional to the concentration of biotin. Standard calibration curves based on the kinetic response are obtained and detection limits of approximately 10(-9)M are established. Because the assay is amenable for use in small volumes of 5-50 microL or bead-based assays, the detection limits can be extended to the femtomole range. Since the assay depends on kinetic analysis, routine quantitation can be achieved without reference to standard curves. The dynamic aspects allow the assay to be extended to a broader range of applications including its use as an indicator of reagent mixing in laminar-flow assays carried out in microfluidic devices.     

On the two-compartment model for estimating the rate and extent of feed degradation in the rumen

An analysis of the compartmental scheme used to determine the rate and extent of ruminal degradation of feeds is presented. Attention is given to the kinetic representation of the degradation of the potentially degradable fraction. Changing the kinetic order of the rate, and introducing indigestible substrate inhibition and microbial activity into its representation, are investigated. This leads to response functions such as the Gompertz and logistic for describing the cumulative disappearance of potentially degradable substrate during in-sacco and in-vitro incubation.     

Reactions between diglycolaldehyde dithioacetals and some nucleophiles

The homogeneous, neutral polysaccharide isolated from the crude polysaccharide of the fruit pulp from bael (Aegle marmelos) contains arabinose, galactose, and glucose in the molar ratios of 2:3:14. The linkages among the different monosaccharide residues were established through methylation analysis and Smith-degradation studies of the polysaccharide. The anomeric configurations of the different glycosyl groups were determined by study of the chromium trioxide oxidation of the acetylated polysaccharide. Results of these experiments have been discussed in order to assess the structure of the neutral polysaccharide.     

Ecto-5′-nucleotidase/CD73 knockdown increases cell migration and mRNA level of collagen I in a hepatic stellate cell line

Ecto-5′-nucleotidase (eNT/CD73, E.C.3.1.3.5) is a glycosyl phosphatidylinositol (GPI)-linked cell-surface protein with several functions, including the local generation of adenosine from AMP, with the consequent activation of adenosine receptors and the salvaging of extracellular nucleotides. It also apparently functions independently of this activity, e.g., in the mediation of cell-cell adhesion. Liver fibrosis can be considered as a dynamic and integrated cellular response to chronic liver injury and the activation of hepatic stellate cells (HSCs) plays a role in the fibrogenic process. eNT/CD73 and adenosine are reported to play an important role in hepatic fibrosis in murine models. Knockdown of eNT/CD73 leads to an increase in mRNA expression of tissue non-specific alkaline phosphatase (TNALP), another AMP-degrading enzyme and thus no alteration is seen in the total ecto-AMPase activity of the cell. eNT/CD73 knockdown also leads to changes in the expression of collagen I and a clear alteration of cell migration. We suggest that eNT/CD73 protein expression controls cell migration and collagen expression in a mechanism independent of changes in nucleotide metabolism.