Controlling soil-transmitted helminthiasis in pre-school-age children through preventive chemotherapy

Pre-school age children account for 10%-20% of the 2 billion people worldwide who are infected with soil-transmitted helminths (STHs): Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm), and Ancylostoma duodenale/Necator americanus (hookworms). Through a systematic review of the published literature and using information collated at World Health Organization headquarters, this paper summarizes the available evidence to support the recommendation that pre-school children should be included in regular deworming programmes. The first section describes the burden of STH disease in this age group, followed by a summary of how infection impacts iron status, growth, vitamin A status, and cognitive development and how STHs may exacerbate other high mortality infections. The second section explores the safety of the drugs themselves, given alone or co-administered, drug efficacy, and the importance of safe administration. The third section provides country-based evidence to demonstrate improved health outcomes after STH treatment. The final section provides country experiences in scaling up coverage of pre-school children by using other large scale public health interventions, including vitamin A programmes, immunization campaigns, and Child Health days. The paper concludes with a number of open research questions and a summary of some of the operational challenges that still need to be addressed.     

Feeding habits of young predatory fishes in marsh creeks situated along the salinity gradient of the Schelde estuary, Belgium and The Netherlands

Fish and macrobenthos were sampled in four different marshes along the salinity gradient of the Schelde estuary, Belgium/Netherlands, to investigate the importance of marsh creeks as foraging grounds for the dominant, larger fish species. The total density and biomass of all the main macrobenthic taxa (Corophium volutator, Nereis diversicolor, Oligochaeta, Macoma baltica and Heteromastus fliliformis) were measured. The feeding habits of the larger predatory fishes (Platichthys flesus, Dicentrarchus labrax) were investigated. Qualitative and quantitative stomach analyses included the calculation of different indices, showing the niche breadth (as diet diversity) and the niche overlap (as similarity between the predators diet) for this habitat. These analyses showed that the two most important benthic prey species for P. flesus were C. volutator and N. diversicolor. D. labrax preyed upon a wider range of species, including C. volutator, N. diversicolor, Crangon crangon, Carcinus maenas and Orchestia spp. The stomach diversity of D. labrax and P. flesus showed differences between the marshes although there was no consistent pattern in diet composition, reflecting the opportunistic nature of feeding by these large predators. The fullness indices of both flounder and sea bass did not differ significantly along the salinity gradient and the estimated minimum consumption by these predators did not indicate a top-down control of the macrobenthic community. The salt marsh creeks seem to provide excess food for the visiting fish species. The benthic prey was present in very high abundances, which may suggest that the typical nursery species such as C. crangon and C. maenas, and early juveniles of P. flesus, D. labrax and Pomatoschistus microps were not preyed upon significantly. This supports the hypothesis that salt marsh creeks provide good refuge areas for nursery species against predation by larger fish.     

Isolation and characterization of avian influenza viruses, including highly pathogenic H5N1, from poultry in live bird markets in Hanoi, Vietnam, in 2001

Since 1997, outbreaks of highly pathogenic (HP) H5N1 and circulation of H9N2 viruses among domestic poultry in Asia have posed a threat to public health. To better understand the extent of transmission of avian influenza viruses (AIV) to humans in Asia, we conducted a cross-sectional virologic study in live bird markets (LBM) in Hanoi, Vietnam, in October 2001. Specimens from 189 birds and 18 environmental samples were collected at 10 LBM. Four influenza A viruses of the H4N6 (n = 1), H5N2 (n = 1), and H9N3 (n = 2) subtypes were isolated from healthy ducks for an isolation frequency of over 30% from this species. Two H5N1 viruses were isolated from healthy geese. The hemagglutinin (HA) genes of these H5N1 viruses possessed multiple basic amino acid motifs at the cleavage site, were HP for experimentally infected chickens, and were thus characterized as HP AIV. These HA genes shared high amino acid identities with genes of other H5N1 viruses isolated in Asia during this period, but they were genetically distinct from those of H5N1 viruses isolated from poultry and humans in Vietnam during the early 2004 outbreaks. These viruses were not highly virulent for experimentally infected ducks, mice, or ferrets. These results establish that HP H5N1 viruses with properties similar to viruses isolated in Hong Kong and mainland China circulated in Vietnam as early as 2001, suggest a common source for H5N1 viruses circulating in these Asian countries, and provide a framework to better understand the recent widespread emergence of HP H5N1 viruses in Asia.     

Sterol transport by the human breast cancer resistance protein (ABCG2) expressed in Lactococcus lactis

The human breast cancer resistance protein (BCRP, also know as ABCG2, MXR, or ABCP) is one of the more recently discovered ATP-binding cassette (ABC) transporters that confer resistance on cancer cells by mediating multidrug efflux. In the present study, we have obtained functional expression of human BCRP in the Gram-positive bacterium Lactococcus lactis. BCRP expression conferred multidrug resistance on the lactococcal cells, which was based on ATP-dependent drug extrusion. BCRP-mediated ATPase and drug transport activities were inhibited by the BCRP-specific modulator fumitremorgin C. To our knowledge these data represent the first example of the functional expression of a mammalian ABC half-transporter in bacteria. Although members of the ABCG subfamily (such as ABCG1 and ABCG5/8) have been implicated in the transport of sterols, such a role has not yet been established for BCRP. Interestingly, the BCRP-associated ATPase activity in L. lactis was significantly stimulated by (i) sterols including cholesterol and estradiol, (ii) natural steroids such as progesterone and testosterone, and (iii) the anti-estrogen anticancer drug tamoxifen. In addition, BCRP mediated the efflux of [3H]estradiol from lactococcal cells. Our findings suggest that BCRP may play a role in the transport of sterols in human, in addition to its ability to transport multiple drugs and toxins.     

Genetic variability in the species Rhizopus stolonifer, assessed by random amplified polymorphic DNA analysis

Rhizopus stolonifer is an important post-harvest pathogenic fungus. Recent taxonomic findings based on morphological and growth characteristics led to a dramatic reduction in the number of accepted species within the genus. The aim of this study was to examine this situation with molecular markers. Twenty-nine R. stolonifer strains isolated from various locations and substrates were characterized by random amplified polymorphic DNA (RAPD) analysis. The numerical analysis of the RAPD data revealed four main clusters with extremely high dissimilarity values, but only low or moderate variability was observed within these groups. These results suggest a high genetic heterogeneity in the case of R. stolonifer: isolates of R. stolonifer var. stolonifer, R. stolonifer var. reflexus and R. niveus displayed species-level genetic distances, which gives rise to considerations that they might be separate species.     

Reversible transport by the ATP-binding cassette multidrug export pump LmrA: ATP synthesis at the expense of downhill ethidium uptake

The ATP dependence of ATP-binding cassette (ABC) transporters has led to the widespread acceptance that these systems are unidirectional. Interestingly, in the presence of an inwardly directed ethidium concentration gradient in ATP-depleted cells of Lactococcus lactis, the ABC multidrug transporter LmrA mediated the reverse transport (or uptake) of ethidium with an apparent K(t) of 2.0 microm. This uptake reaction was competitively inhibited by the LmrA substrate vinblastine and was significantly reduced by an E314A substitution in the membrane domain of the transporter. Similar to efflux, LmrA-mediated ethidium uptake was inhibited by the E512Q replacement in the Walker B region of the nucleotide-binding domain of the protein, which strongly reduced its drug-stimulated ATPase activity, consistent with published observations for other ABC transporters. The notion that ethidium uptake is coupled to the catalytic cycle in LmrA was further corroborated by studies in LmrA-containing cells and proteoliposomes in which reverse transport of ethidium was associated with the net synthesis of ATP. Taken together, these data demonstrate that the conformational changes required for drug transport by LmrA are (i) not too far from equilibrium under ATP-depleted conditions to be reversed by appropriate changes in ligand concentrations and (ii) not necessarily coupled to ATP hydrolysis, but associated with a reversible catalytic cycle. These findings and their thermodynamic implications shed new light on the mechanism of energy coupling in ABC transporters and have implications for the development of new modulators that could enable reverse transport-associated drug delivery in cells through their ability to uncouple ATP binding/hydrolysis from multidrug efflux.     

Effects of staurosporine,U-73122, wortmannin, 4-hydroxynonenal and sodium azide upon the release of secreted β-amyloid precursor protein from human platelets in response to thrombin stimulation

In the present study, the release of secreted -amyloid precursor protein (APPs) in response to thrombin stimulation in platelets has been investigated. Incubation of platelets with thrombin produced a concentration-dependent release of APPs with a concomitant reduction in the APP remaining in the lysates. The response to thrombin was not affected by pretreatment for 15 min with the phospholipase C inhibitor U-73122, with the protein kinase C inhibitor staurosporine, or with hydrogen peroxide (which at the concentrations used affects the phosphoinositide signalling system in human platelets). In contrast, pretreatment with wortmannin and sodium azide reduced the responses to thrombin. These data would suggest that thrombin may cause the release of APPs from human platelets via an activation of a phospholipase C-independent pathway. Thrombin-stimulated APPs release was also reduced by 4-hydroxynonenal. This finding, if it is a phenomenon also found for CNS cells, could be of relevance to the pathogenesis of Alzheimer's disease, given that an accumulation of 4-hydroxynonenal is found in this disease.