Scaling up of tsetse control to eliminate Gambian sleeping sickness in northern Uganda

BackgroundTsetse flies (Glossina) transmit Trypanosoma brucei gambiense which causes Gambian human African trypanosomiasis (gHAT) in Central and West Africa. Several countries use Tiny Targets, comprising insecticide-treated panels of material which attract and kill tsetse, as part of their national programmes to eliminate gHAT. We studied how the scale and arrangement of target deployment affected the efficacy of control.Methodology and principal findingsBetween 2012 and 2016, Tiny Targets were deployed biannually along the larger rivers of Arua, Maracha, Koboko and Yumbe districts in North West Uganda with the aim of reducing the abundance of tsetse to interrupt transmission. The extent of these deployments increased from ~250 km² in 2012 to ~1600 km² in 2015. The impact of Tiny Targets on tsetse populations was assessed by analysing catches of tsetse from a network of monitoring traps; sub-samples of captured tsetse were dissected to estimate their age and infection status. In addition, the condition of 780 targets (~195/district) was assessed for up to six months after deployment. In each district, mean daily catches of tsetse (G. fuscipes fuscipes) from monitoring traps declined significantly by >80% following the deployment of targets. The reduction was apparent for several kilometres on adjacent lengths of the same river but not in other rivers a kilometre or so away. Expansion of the operational area did not always produce higher levels of suppression or detectable change in the age structure or infection rates of the population, perhaps due to the failure to treat the smaller streams and/or invasion from adjacent untreated areas. The median effective life of a Tiny Target was 61 (41.8–80.2, 95% CI) days.ConclusionsScaling-up of tsetse control reduced the population of tsetse by >80% across the intervention area. Even better control might be achievable by tackling invasion of flies from infested areas within and outside the current intervention area. This might involve deploying more targets, especially along smaller rivers, and extending the effective life of Tiny Targets.     

Documenting a thousand years of environmental and anthropogenic changes on mangroves on the Bangkok coast,the upper Gulf of Thailand

Vegetation History and Archaeobotany - Environmental changes and human activities in a mangrove ecosystem in Bang Khun Thian, south of Bangkok, the upper Gulf of Thailand were reconstructed through...     

Detection of photomutagens in natural and synthetic fuels

The contribution of non-ionizing radiation to synfuel-related skin carcinogenesis is largely unknown. We have employed a modification of the Salmonella histidine reversion test system to detect photomutation by various fuel substances. For photomutation testing we washed and resuspended cells in buffer, irradiated with 'visible' light in the presence of test substance, and removed aliquots after various light exposures for assay by the plate incorporation method. We have assayed photomutagenicity and microsome-mediated mutagenicity of a crude petroleum, a shale oil, and coal hydrogenation process intermediates. Photomutagenicity was studied using one concentration of each oil; peak revertants per plate for most oils tested were relatively similar to revertants per plate with microsomal activation of the same oil at the corresponding concentration. The shale oil was an exception to this pattern: with light activation, peak revertant numbers per plate were approximately 10 times the value observed with microsomal activation. The samples tested are not assumed to be representative of all petroleums, shale oils or coal oils. Our results do suggest that environmental radiation may be a significant factor in synfuel-related skin carcinogenesis and that photomutagens may be different from enzyme-activatable promutagens.     

Noncovalent drug-DNA binding interactions that inhibit and stimulate (A)BC excinuclease.

(A)BC excinuclease from Escherichia coli catalyzes the initial step of nucleotide excision repair. It recognizes and binds to many types of covalent modifications in DNA and incises the damaged strand on both sides of the lesion. We employed a variety of noncovalent DNA binding drugs to examine in vitro the mechanisms and the nature of the DNA-drug interactions responsible for two phenomena: inhibition of excision repair by caffeine and other noncovalent DNA binding compounds; incision of undamaged DNA produced by (A)BC excinuclease in the presence of the bisintercalating drug ditercalinium. All of the chemicals examined (e.g., actinomycin D, caffeine, ethidium bromide, and Hoechst 33258) inhibited incision of a covalent adduct by (A)BC excinuclease, and direct evidence is given for a common mechanism in which UvrA is depleted by binding to drug-undamaged DNA complexes. In the absence of significant amounts of undamaged DNA, another mechanism of inhibition was observed, in which enzyme bound to noncovalent drug-DNA complexes in the vicinity of the lesion prevents formation of preincision complexes at the lesion. Ditercalinium and unexpectedly all of the other drugs examined promoted the incision of undamaged DNA when the enzyme was present at high concentration. Thus, this activity contrary to previous assumptions is not unique to bisintercalators. Another unexpected finding was stimulation of incision at certain sites of photodamage in DNA produced by low concentrations of noncovalent DNA binding chemicals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of the reticulum in the stability and shape of the isolated human erythrocyte membrane

In order to examine the widely held hypothesis that the reticulum of proteins which covers the cytoplamsic surface of the human erythrocyte membrane controls cell stability and shape, we have assessed some of its properties. The reticulum, freed of the bilayer by extraction with Triton X-100, was found to be mechanically stable at physiological ionic strength but physically unstable at low ionic strength. The reticulum broke down after a characteristic lag period which decreased 500-fold between 0 degrees and 37 degrees C. The release of polypeptide band 4.1 from the reticulum preceded that of spectrin and actin, suggesting that band 4.1 might stabilize the ensemble but is not essential to its integrity. The time-course of breakdown was similar for ghosts, the reticulum inside of ghosts, and the isolated reticulum. However, at very low ionic strength, the reticulum was less stable within the ghost than when free; at higher ionic strength, the reverse was true. Over a wide range of conditions the membrane broke down to vesicles just as the reticulum disintegrated, presumably because the bilayer was mechanically stabilized by this network. The volume of both ghosts and naked reticula varied inversely and reversibly with ionic strength. The volume of the naked reticulum varied far more widely than the ghost, suggesting that its deformation was normally limited by the less extensible bilayer. The contour of the isolated reticulum was discoid and often dimpled or indented, as visualized in the fluorescence microscope after labeling of the ghosts with fluoroscein isothiocyanate. Reticula derived from ghosts which had lost the ability to crenate in isotonic saline were shriveled, even though the bilayer was smooth and expanded. Conversly, ghosts crenated by dinitrophenol yielded smooth, expanded reticula. We conclude that the reticulum is a durable, flexible, and elastic network which assumes and stabilizes the contour of the membrane but is not responsible for its crenation.     

A simple method for maintaining high multiplication of Narcissus shoot cultures in vitro

A simple method for stimulating and maintaining high in vitro multiplication of Narcissus shoot clump cultures was developed. Shoot clumps were subjected either to normal cutting where leaves were trimmed to 20 mm in length at the beginning of each culture passage or to severe cutting where shoot clumps were cut down to the basal plate region removing all green tissue. Severe cutting at the beginning of each culture passage initially doubled the leaf multiplication, compared to normal cutting, but the difference between cutting treatments declined in successive passages. The improvement in leaf multiplication was maintained when shoot clumps were subjected to severe cutting only at every other culture passage, with no cutting in the alternate recovery passages. In vitro multiplication was increased by severe cutting in all seven Narcissus cultivars which were tested.Abbreviations NAA-1 naphthylacetic acid - BAP benzylaminopurine     

The effect of Plasmodium berghei and Trypanosoma brucei infections on the immune expulsion of the nematode Trichuris muris from mice

The effects of concurrent P. berghei or T. brucei infections on the immune expulsion of primary and challenge infections of T. muris from CFLP strain mice have been examined. CFLP mice usually expel the nematode 18–21 days after a primary infection and within 4–6 days after a challenge infection. Both acute malaria and trypanosome infections initiated at the same time as the T. muris infection suppressed worm expulsion; when the protozoal infections were started 7 days after the T. muris infection worm expulsion was suppressed in a proportion of the mice. Acute trypanosome and malaria infections delayed the expulsion of a challenge infection from immune mice, but in the case of P. berghei the delay was short-lived.     

Transfer of immunity against Trichuris muris in the mouse by serum and cells

Transfer of immunity against Trichuris muris in the mouse by serum and cells. Internationaljournal for Parasitology 3: 717–722. A protective immunity against the nematode Trichuris muris was transferred with antiserum and cells taken from immunized mice. Immunity was transferred most reliably by cells, especially mesenteric lymph node cells, but most effectively by serum. The protective capacity of serum and cells taken from the same mice was not always related. Multiple immunization of the donors did not markedly increase protection in the recipients.