Evaluation of alternative tactics for management of insecticide-resistant horn flies (Diptera: Muscidae)

A 3-yr study was conducted to determine the efficacy of tactics that could be used to manage populations of insecticide-resistant horn flies, Hematobia irritans irritans (L.). Insecticide spray, spot-on or pour-on formulations and two IGRs in bolus formulation, 1.3- and 3.2-ha pasture rotations on different rotation schedules, 0-50% Brahman breeding, selected fly-resistant cows, and a mechanical trap were evaluated singly and in combination. Concentration-mortality tests indicated that horn flies collected from cows used in the current study were significantly less susceptible to diazinon, coumaphos, and methoxychlor than horn flies from cows at the same locations previously used to determine baseline susceptibility. During the 3-yr study at the Southeast Research and Extension Center (SEREC), the IGR-bolus significantly reduced (P < 0.05) horn fly numbers on both the continuous and rotational graze regimens, resulting in significantly (P < 0.05) greater calf weaning weights (average of 24 kg). Horn fly numbers were significantly greater on untreated cows during the 3-yr study at the Southwest Research and Extension Center (SWREC) compared with the mean fly numbers on cows that received fly-management treatments. All tactics and tactic-combinations used at SWREC on cattle having no Brahman breeding failed to significantly reduce insecticide-resistant horn fly numbers. However, the combination of Brahman breeding with the IGR-Bolus and mechanical trap significantly reduced horn fly numbers and resulted in significant increases in calf weaning weight. In addition, mean horn fly numbers decreased significantly as the percentage Brahman breeding increased with 50% Brahman breeding reducing horn fly numbers by 140 flies per cow. No significant difference was found between the mean fly numbers on the fly-resistant purebred group and the cows that had no Brahman breeding but received the IGR-Bolus or used the mechanical trap. The use of synergized zeta-cypermethrin pour-on treatment successfully complimented the use of IGR-bolus and mechanical traps in reducing insecticide-resistant horn fly numbers. Neither 1.3- nor 3.2-ha size paddocks and stocking rates used in the rotation graze regimens at SEREC and SWREC, respectively, significantly reduced horn fly numbers when compared with continuously grazed paddocks. Data indicated the importance of using tactics that reduce horn fly numbers to approximately 150 horn flies per cow. These data demonstrated the efficacy of using tactic combinations to manage insecticide-resistant horn fly populations.     

Free and Conjugated Amines in Human Lumbar Cerebrospinal Fluid

Significant amounts of acid-hydrolyzable conjugates of 3,4-dihydroxyphenylethylamine, norepinephrine, and 5-hydroxytryptamine were detected in lumbar CSF from 22 awake unpremedicated healthy individuals. In the CSF samples, the amounts of conjugated amines almost always exceeded the amounts of free amines, but were less than the amounts of the acid metabolites 3,4-dihydroxyphenylacetic acid, homovanillic acid, and 5-hydroxyindoleacetic acid.     

Concurrent separation of catecholamines, dihydroxyphenylglycol, vasoactive intestinal peptide, and neuropeptide Y in superfusate and tissue extract

A method is described for separation and quantification of 3,4-dihydroxyphenylglycol (DO-PEG), norepinephrine (NE), dopamine (DA), vasoactive intestinal peptide (VIP), and neuropeptide Y (NPY) from single samples of tissue homogenate and from superfusate from in vitro dog blood vessel preparations using cartridges containing 0.4 g of octadecylsilane (Sep-Pak C-18). Samples were passed through the cartridge at pH 7.4. A step-gradient system was used to first selectively desorb the catechols (DOPEG, NE, DA) with a moderately polar eluent; subsequently VIP and NPY were eluted with 2.5 ml of a mixture of 1% trifluoroacetic acid, 80% acetonitrile. Five Sep-Pak catechol eluents were tested. Catechols were quantified by HPLC with electrochemical detection and peptides by radioimmunoassay. An HPLC solvent system is described which is particularly useful for chromatography of the more hydrophilic catechols DOPEG, 3,4-dihydroxymandelic acid, and 3,4-dihydroxyphenylalanine concurrently with catecholamines. For superfusion studies, sample cleanup time was reduced to about 4 min per sample by attachment of the cartridges directly to the bottom of the superfusion chamber. Superfusate was subsequently pulled through the cartridges immediately after they were passed over the tissue. Batches of 12 high-speed tissue supernates were processed through the method in about 30 min. The method was used to analyze DOPEG, NE, DA, VIP, and NPY in various rat and dog tissues. The values obtained were similar to values obtained previously by other methods. Because the catechols and peptides are separated from a single sample, the method has several advantages over those described previously; e.g., it is rapid, simple, and more sensitive.     

Topological studies on the enzymes catalyzing the biosynthesis of Glc-P- dolichol and the triglucosyl cap of Glc3Man9GlcNAc2-P-P-dolichol in microsomal vesicles from pig brain: use of the processing glucosidases I/II as latency markers

In the current model for Glc3Man9GlcNAc2-P-P-Dol assembly, Man5GlcNAc2- P-P-Dol, Man-P-Dol, and Glc-P-Dol are synthesized on the cytoplasmic face of the ER and diffuse transversely to the lumenal leaflet where the synthesis of the lipid-bound precursor oligosaccharide is completed. To establish the topological sites of Glc-P-Dol synthesis and the lipid-mediated glucosyltransfer reactions involved in Glc3Man9GlcNAc2-P-P-Dol synthesis in ER vesicles from pig brain, the trypsin-sensitivity of Glc-P-Dol synthase activity and the Glc-P- Dol:Glc0-2Man9GlcNAc2-P-P-Dol glucosyltransferases (GlcTases) was examined in sealed microsomal vesicles. Since ER vesicles from brain do not contain glucose 6-phosphate (Glc 6-P) phosphatase activity, the latency of the lumenally oriented, processing glucosidase I/II activities was used to assess the intactness of the vesicle preparations. Comparative enzymatic studies with sealed ER vesicles from brain and kidney, a tissue that contains Glc 6-P phosphatase, demonstrate the reliability of using the processing glucosidase activities as latency markers for topological studies with microsomal vesicles from non-gluconeogenic tissues lacking Glc 6-P phosphatase. The results obtained from the trypsin-sensitivity assays with sealed microsomal vesicles from brain are consistent with a topological model in which Glc-P-Dol is synthesized on the cytoplasmic face of the ER, and subsequently utilized by the three Glc-P-Dol-mediated GlcTases after "flip-flopping" to the lumenal monolayer.      

Mitochondrial gene divergence of Colombian Drosophila pseudoobscura

Isolated populations of drosophila pseudoobscura, separated from North American populations by about 2,400 km, were found in Colombia in 1960. We compared for sequences of the small ribosomal RNA (srRNA) gene on the mitochondria between North American and Colombian D. pseudoobscura in order to clarify the age of the Colombian isolates. The North American populations were not genetically different from each other but were genetically different from the Colombian populations. The Mexican strains represent the area from which the Colombian founders might have come. The estimated net nucleotide divergence between Mexican and Colombian D. pseudoobscura indicates that the Colombian population is not an ancient lineage. Phylogenies using both distance and parsimony methodologies reinforced this conclusion. The Colombian samples group together with both methods but, according to the bootstrap analysis, not significantly. It appears that the populations have not been separated long enough for their DNA sequences to show much divergence.      

Dihydroxyphenylalanine and Dopamine Are Released from Portal Vein Together with Noradrenaline and Dihydroxyphenylglycol During Nerve Stimulation

The overflows of 3,4-dihydroxyphenylalanine, dopamine, noradrenaline, and 3,4-dihydroxyphenylglycol in canine portal vein superfused in vitro were studied before, during, and after depolarization of sympathetic nerve endings. The four compounds were separated from superfusate and from tissue on Sep-Pak C-18 cartridges and quantified by HPLC with electrochemical detection. Physiological and biochemical methods were used to show that the compound released was most probably 3,4-dihydroxyphenylalanine; the identity of the other endogenous compounds has been established previously. Release of 3,4-dihydroxyphenylalanine was calcium and frequency dependent, inhibited by a-m-L-p-tyrosine (an inhibitor of tyrosine hydroxylase) and augmented by 3-hydroxybenzylhydrazine (an inhibitor of aromatic amino acid decarboxylase). The overflows of dopamine, noradrenaline, and 3,4-dihydroxyphenylglycol from the vein were calcium and frequency dependent. It was estimated that under control conditions, approximately 80% of the total 3,4-dihydroxyphenylalanine that was synthesized was directed to catecholamine biosynthesis, approximately 8% overflowed from the vein, and approximately 14% remained unchanged within the tissue. It is concluded that 3,4-dihydroxyphenylalanine and dopamine are released together with noradrenaline and 3,4-dihydroxyphenylglycol from portal vein upon nerve depolarization.     

Wildlife detector dogs and camera traps: a comparison of techniques for detecting feral cats

A major challenge in controlling overabundant wildlife is monitoring their populations, particularly as they decline to very low density. Camera traps and wildlife detector dogs are increasingly being used for this purpose. We compared the cost-effectiveness of these two approaches for detecting feral cats (Felis catus) on two pastoral properties in Hawke's Bay, North Island, New Zealand. One property was subject to intensive pest removal, while the other had no recent history of pest control. Camera traps and wildlife detector dogs detected cats at similar rates at both sites. The operating costs of each method were also comparable. We identify a number of advantages and disadvantages of each technique, and suggest priorities for further research.