Efficacy of native and recombinant Cry1B protein against experimentally induced and naturally acquired ovine myiasis (fly strike) in sheep

Several hundred strains of Bacillus thuringiensis (Bt), isolated in New Zealand from samples of soil and sheep fleece, were tested for toxicity to larvae of the blowfly Lucilia cuprina Wiedemann. Characterization of the Bt strains revealed that three of the more active strains produced Cry1Ba (an insecticidal protein present in Bt mother cell crystal inclusion) that was toxic to blowflies. These strains were evaluated for the ability to prevent experimentally induced fly strike in a bioassay by using first instars. Results with undiluted spore/crystal preparations were variable, but they generally prevented fly strike on sheep maintained on pasture for 3-6 wk. Spore viability was satisfactory throughout the trials and environmental factors (e.g., precipitation and UV radiation) seemed to have minimal effect on persistence. The loss of fly strike protection in these experiments correlated with the movement of spore/crystal toxicity away from the skin as a result of wool growth. Solubilized protein preparations were not as potent as spore/crystal preparations and fly strike protection lasted only from 1 to 3 wk. Vegetative forms of the Cry1Ba-producing strains of Bt did not establish on the fleece of sheep, did not produce significant sporulation, and no protection against fly strike was achieved. Escherichia coli expressing recombinant Cry1Ba protein was toxic to larvae in vitro but did not effectively protect sheep from fly strike because blowfly larvae were able to establish readily 8 d posttreatment. In a single field experiment involving 80 sheep per group, a spore/crystal preparation from a Bt strain expressing Cry1Ba provided less protection from naturally acquired fly strike than afforded by a commercially available dip.     

Reservoirs of antibiotic resistance genes

A potential concern about the use of antibiotics in animal husbundary is that, as antibiotic resistant bacteria move from the farm into the human diet, they may pass antibiotic resistance genes to bacteria that normally reside in a the human intestinal tract and from there to bacteria that cause human disease (reservoir hypothesis). In this article various approaches to evaluating the risk of agricultural use of antibiotics are assessed critically. In addition, the potential benefits of applying new technology and using new insights from the field of microbial ecology are explained.     

Effect of acute sympathetic nervous system activation on flow-mediated dilation of brachial artery

We tested the hypothesis that flow-mediated dilation (FMD) of the brachial artery would be impaired by acute increases in sympathetic nervous system activity (SNA) in models where similar peak shear stress stimulus was achieved by varying the duration of forearm muscle ischemia. Eleven healthy young men were studied under four different conditions, each with its own control: lower body suction (LBS), cold pressor test (CPT), mental arithmetic task (MAT), and activation of muscle chemoreflex (MCR). The duration of ischemia before observation of FMD by ultrasound imaging was 5 min each for control, LBS, and CPT; 3 min for MAT; and 2-min for MCR. Peak shear rate was not different between control and any of the SNA conditions, although total shear in the first minute was reduced in MAT. MCR was the only condition in which brachial artery vasoconstriction was observed before forearm occlusion [4.38 (SD 0.53) vs. control 4.60 (SD 0.53) mm, P < 0.05]; however, diameter increased to the same absolute value as that of the control, so the percent FMD was greater for MCR [9.85 (SD 2.33) vs. control 5.29 (SD 1.50)%]. Blunting of the FMD response occurred only in the CPT model [1.51 (SD 1.20)%]. During SNA, the increase in plasma cortisol from baseline was significant only for MCR; the increase in plasma norepinephrine was significant for MCR, LBS, and CPT; and the increase in epinephrine was significant only for MCR. These results showed that the four models employed to achieve increases in SNA had different effects on baseline brachial artery diameter and that blunted FMD is not a general response to increased SNA.     

Paleopolyploidy and gene duplication in soybean and other legumes

Two of the most important observations from whole-genome sequences have been the high rate of gene birth and death and the prevalence of large-scale duplication events, including polyploidy. There is also a growing appreciation that polyploidy is more than the sum of the gene duplications it creates, in part because polyploidy duplicates the members of entire regulatory networks. Thus, it may be important to distinguish paralogs that are produced by individual gene duplications from the homoeologous sequences produced by (allo)polyploidy. This is not a simple task, for several reasons, including the chromosomally cryptic nature of many duplications and the variable rates of gene evolution. Recent progress has been made in understanding patterns of gene and genome duplication in the legume family, specifically in soybean.     

Heritable transgenesis of Parastrongyloides trichosuri: a nematode parasite of mammals

Germline transformation of a parasitic nematode of mammals has proven to be an elusive goal. We report here the heritable germline transformation of Parastrongyloides trichosuri, a nematode parasite whose natural hosts are Australian possums of the genus Trichosurus. This parasite can undergo multiple free-living life cycles and these replicative cycles can be maintained indefinitely in the laboratory. Transformation was achieved by microinjection of DNA into the ovary syncytium of either free-living or parasitic adult females. By selecting for the transgenic progeny of successive free-living life cycles, it was possible to establish and maintain transgenic lines. All three transgenic lines tested were shown capable of establishing patent infections in possums and to transmit the functional transgene to their progeny. The transgene, driven by the Pt hsp-1 promoter, was constitutively expressed in intestinal cells at all stages of both parasitic and free-living life cycles, although gene silencing appears to occur in some transgenic progeny. This is the first report of heritable transgenesis in a parasitic nematode of a mammal and we discuss a variety of previously inaccessible experimental avenues that will now be possible with this powerful model system.     

Differential regulation of sympathetic burst frequency and amplitude following acute hypoxia in humans

Current evidence suggests that the persistent sympathetic nerve activity (SNA), commonly observed after exposure to hypoxia (HX), is mediated by chemoreceptor sensitization and or baroreflex resetting. Evidence in humans and animals suggests that these reflexes may independently regulate the frequency (gating) and amplitude (neuronal recruitment) of SNA bursts. In humans (n = 7), we examined the regulation of SNA following acute isocapnic HX (5 min; end-tidal Po(2) = 45 Torr) and euoxic hypercapnia (HC; 5 min; end-tidal Pco(2) = +10 from baseline). HX increased SNA burst frequency (21 ± 7 to 28 ± 8 bursts/min, P < 0.05) and amplitude (99 ± 10 to 125 ± 19 au, P < 0.05) as did HC (14 ± 6 to 22 ± 10 bursts/min, P < 0.05 and 100 ± 12 to 133 ± 29 au, P < 0.05, respectively). Burst frequency (26 ± 7 bursts/min, P < 0.05), but not amplitude (97 ± 12 au), remained elevated 10 min post-HX. The change in burst amplitude (but not frequency) was significantly related to the measured change in ventilation (r(2) = 0.527, P < 0.001). Both frequency and amplitude decreased during recovery following HC. These data indicate the differential regulation of pattern and magnitude of sympathetic outflow in humans with sympathetic persistence following HX being specific to burst frequency and not amplitude.     

Ichthyophthirius multifiliis as a potential vector of Edwardsiella ictaluri in channel catfish

There is limited information on whether parasites act as vectors to transmit bacteria in fish. In this trial, we used Ichthyophthirius multifiliis and fluorescent Edwardsiella ictaluri as a model to study the interaction between parasite, bacterium, and fish. The percentage (23-39%) of theronts fluorescing after exposure to E.?ictaluri was significantly higher than control theronts (~?6%) using flow cytometry. Theronts exposed to E.?ictaluri at 4?×?10(7) CFU?mL(-1) showed a higher percentage (~?60%) of fluorescent theronts compared to those (42%) exposed to 4?×?10(3) CFU?mL(-1) at 4?h. All tomonts (100%) carried the bacterium after exposure to E.?ictaluri. Edwardsiella ictaluri survived and replicated during tomont division. Confocal microscopy demonstrated that E.?ictaluri was associated with the tomont surface. Among theronts released from tomonts exposed to E.?ictaluri, 31-66% were observed with attached E.?ictaluri. Sixty percent of fish exposed to theronts treated with 5?×?10(7) E.?ictaluri?mL(-1) were positive for E.?ictaluri at 4?h as determined by qPCR or fluorescent microscopy. Fluorescent E.?ictaluri were observed on trophonts in skin and gill wet mounts of dead fish. This study demonstrated that Ich could vector E.?ictaluri to channel catfish.