The influence of 'time since last blood meal' on the toxicity of essential oils to the poultry red mite (Dermanyssus gallinae)

The poultry red mite, Dermanyssus gallinae (De Geer) is a serious ectoparasitic pest of layer hens that can survive for long periods in the poultry house sub-structure without taking a blood meal from its host. The research undertaken in this study found that 'time since last blood meal' had a notable effect on how toxic a selection of plant essential oils were to D. gallinae under laboratory conditions. In general, the essential oils had a greater toxic effect on D. gallinae if mites had been starved of a blood meal for around 3 weeks, than if they had been more recently fed 3-13 days prior to tests. This result was consistent across the four essential oils used (thyme, palmarosa, caraway and juniper leaf). This suggests that plant essential oils may be of use in management schemes for D. gallinae, particularly if used to sanitise houses between flocks, when mites will have been starved.     

Influence of tropical seasonal changes on oocyte diameter, responses to hormonal induction and hatching quality in two strains of the catfish, Heterobranchus longifilis Val. (Clariidae)

A comparison was made between the oocyte diameter, pseudo‐absolute fecundity (PAF) and egg quality of two strains of the catfish, Heterobranchus longifilis, maintained in outdoor ponds under a tropical highland climate in Cameroon. The results indicated that circannual endogenous rhythms for ovarian recrudescence and regression are absent in H. longifilis, irrespective of breeding history, age and strain. There appeared to be a possible slight adverse effect of climate (dry season) on reproductive performance of both strains. Oocyte diameter and PAF increased with increasing fish weight when data from both strains were combined, indicating that the two strains may exhibit the same reproductive performance. Viable eggs were obtained all year round after hormonal induction. It is concluded that for propagation of H. longifilis in tropical African countries, broodfish could be maintained in outdoor earthen fish ponds with proper feeding.     

Effects of genetic strain and holding facility on the characteristics of alkaline phosphatase and brush border enzymes in silver perch (Bidyanus bidyanus)

The activity of the enzymes located in the digestive tract (pyloric caeca and intestine) in two strains and F₁ crosses of the Australian freshwater fish silver perch [Murray River (M) and Cataract Dam (C)] was evaluated. The effect of the fish holding system (cages or ponds) on the activity of alkaline phosphatase (AP) and the brush border enzymes: maltase, leucine amino peptidase (LAP) and γ‐glutamyl transferase (γ‐GT) was examined. The enzymatic activity was tested in three intestinal sections: the pyloric caeca, upper and lower intestine. All the tested enzyme activities were influenced by an interaction between the intestinal section and the strain or cross of silver perch. For fish maintained in ponds, there were two distinct enzymatic activity patterns, one for the pure strains (C × C and M × M) and one for the crosses (C × M and M × C). Significantly higher (P<0.05) enzymatic activities of the crosses compared with the pure strains were particularly noticeable in the pyloric caeca. In fish held in cages, there was a significantly higher (P<0.05) enzymatic activity in the pyloric caeca of the C × C strain. The total enzymatic activities in the fish reared in the ponds were significantly higher (P<0.05) than those in the fish held in cages. The results of the present investigation confirm that the different genetic background of the silver perch in the Murray River and in the Cataract Dam influences the activity of the brush border digestive enzymes. This activity also varies between maintenance systems.     

Effect of pH, temperature, and moisture on the formation of volatile compounds in glycine/glucose model systems

Mixtures of glycine, glucose, and starch were extrusion cooked using sodium hydroxide at 0, 3, and 6 g/L of extruder water feed, 18% moisture, and 120, 150, and 180 degrees C target die temperatures, giving extrudates with pH values of 5.6, 6.8, and 7.4. Freeze-dried equimolar solutions of glucose and glycine were heated either dry or after equilibration to approximately 13% moisture at 180 degrees C in a reaction-tube system designed to mimic the heating profile in an extruder. Volatile compounds were isolated onto Tenax and analyzed by gas chromatography-mass spectrometry. For the extrudates, total yields of volatiles increased with decreasing pH at 180 degrees C, reached a maximum at pH 6.8 at 150 degrees C, and increased with increasing pH at 120 degrees C. Amounts increased with temperature at all pH values. Pyrazines were the most abundant class for all sets of conditions (54-79% of total volatiles). Pyrroles, ketones, furans, oxazoles, and pyridines were also identified. Yields of volatiles from the reaction-tube samples increased by >60% in the moist system. Levels of individual classes also increased in the presence of moisture, except pyrazines, which decreased approximately 3.5-fold. Twenty-one of the compounds were common to the reaction-tube samples and the extrudates.     

Event-specific plasmid standards and real-time PCR methods for transgenic Bt11, Bt176, and GA21 maize and transgenic GT73 canola

Since the 18th of April 2004, two new regulations, EC/1829/2003 on genetically modified food and feed products and EC/1830/2003 on traceability and labeling of GMOs, are in force in the EU. This new, comprehensive regulatory framework emphasizes the need of an adequate tracing system. Unique identifiers, such as the transgene genome junction region or a specific rearrangement within the transgene DNA, should form the basis of such a tracing system. In this study, we describe the development of event-specific tracing systems for transgenic maize lines Bt11, Bt176, and GA21 and for canola event GT73. Molecular characterization of the transgene loci enabled us to clone an event-specific sequence into a plasmid vector, to be used as a marker, and to develop line-specific primers. Primer specificity was tested through qualitative PCRs and dissociation curve analysis in SYBR Green I real-time PCRs. The primers were then combined with event-specific TaqMan probes in quantitative real-time PCRs. Calibration curves were set up both with genomic DNA samples and the newly synthesized plasmid DNA markers. It is shown that cloned plasmid GMO target sequences are perfectly suitable as unique identifiers and quantitative calibrators. Together with an event-specific primer pair and a highly specific TaqMan probe, the plasmid markers form crucial components of a unique and straighforward tracing system for Bt11, Bt176, and GA21 maize and GT73 canola events.     

Influence of acidification and aluminum on the density and biomass of lotic benthic invertebrates

Experiments were carried out in plasticized wooden channels fed by a small creek in the Reserve des Laurentides, 80 km north of Quebec city. Channels were naturally colonized by invertebrates for 65 d before treatment. Treated channels were acidified in August with dilute H₂SO₄ only, or with acid plus a solution of Al sulfate (final concentration of 0.19 mg L^?1). The control channel received creek water only (pH 6.3 to 6.9). The addition of Al had no effect on invertebrate density and biomass. After 73 d of acidification, invertebrate densities were only one third the number found in the control channel. Invertebrate hiomass was not different within channels, although biomass was generally higher in the two acidified channels. Difference in densities between acidified and non-acidified channels was attributed to lack of colonization and not to an increase in drift. Microtendipes, a large and resistant larva of Chironomidae constituted a large fraction of the hiomass, largely outweighing numerous very small larvae. Effects on the density were attributed to the direct effect of low pH and not to indirect action through food limitations.     

Relatively rapid loss of lampricide residues from fillet tissue of fish after routine treatment

The selective sea lamprey (Petromyzon marinus) larvicide 3-trifluoromethyl-4-nitrophenol (TFM) is currently used to control parasitic sea lampreys in tributaries to the Great Lakes basin. The concentration and persistence of TFM and its major metabolite, TFM glucuronide (TFM-glu), was determined in fillet tissue of fish after a typical stream application. Rainbow trout (Oncorhynchus mykiss) and channel catfish (Ictalurus punctatus) were exposed to a nominal concentration of 12.6 nmol/mL TFM for about 12 h during a sea lamprey control treatment of the Ford River in Michigan. Concentrations of TFM and TFM-glu were greatest in the fillet tissues during the exposure period, with greater residues in channel catfish (wet wt; mean, 6.95 nmol/g TFM; mean, 2.40 nmol/g TFM-glu) than in rainbow trout (wet wt; mean, 1.45 nmol/g TFM; mean, 0.93 nmol/g TFM-glu). After the exposure period, residues in both species decreased by 90-99% within 6-12 h and were less than the quantitation limit (<0.03 nmol/g) within 36 h.