Impregnated bednets and the dose-severity relationship in malaria

The finding that insecticide-impregnated bednets decrease symptomatic malaria and death more than infection has been interpreted as providing evidence that dose influences seventy o f disease in malaria. The complications o f this argument in areas where much o f the population has a background parasitaemia have already been considered. In this article, Judith Glynn, Jo Lines and David Bradley explore whether or not the results of impregnated bednet trials can help to determine the existence of a dose-severity relationship for malaria.     

Time course of metabolism of aldrin and dieldrin by suspension cultures

Time course, up to 100d, of uptake and metabolism of aldrin and dieldrin added at subculture to suspension cultures from Phaseolus vulgaris (French bean) root and shoot, and Solanum tuberosum (potato) tuber comparable, with rapid dieldrin production and delayed appearance of other metabolites. When aldrin and dieldrin not added to Phaseolus cultures until 10 or 20d after subculture usual extent of conversion of aldrin to dieldrin, but reduced production of other metabolites, and growth inhibition negated. Increasing volumes of 2-methoxyethanol had detrimental effect on growth and uptake and metabolism. Dieldrin production maximal during rapid growth phase and probably independent of other conversions.     

Nephrogenic diabetes insipidus in an Australian aboriginal kindred.

Four Australian aboriginal children were found to have nephrogenic diabetes insipidus. They are the sons of 3 sisters who were shown to have a urinary concentrating defect uncorrected by vasopressin. An extensive genealogy did not reveal any caucasian genetic influence suggesting that a new genetic mutation was responsible.     

Elevated co2 has Differential Effects on Five Species of Microalgae from a Subtropical Freshwater Lake: Possible Implications for Phytoplankton Species Composition

Rising atmospheric CO₂ concentrations are predicted to have a significant impact on global phytoplankton populations. Of particular interest in freshwater systems are those species that produce toxins or impact water quality, though evidence for how these species, and many others, will respond is limited. This study investigated the effects of elevated CO₂ (1,000 ppm) relative to current atmospheric CO₂ partial pressures (400 ppm), on growth, cell size, carbon acquisition, and photophysiology of five freshwater phytoplankton species including a toxic cyanophyte, Raphidiopsis raciborskii, from Lake Wivenhoe, Australia. Effects of elevated CO₂ on growth rate varied between species; notably growth rate was considerably higher for Staurastrum sp. and significantly lower for Stichococcus sp. with a trend to lower growth rate for R. raciborskii. Surface area to volume ratio was significantly lower with elevated CO₂, for all species except Cyclotella sp. Timing of maximum cell concentrations of those genera studied in monoculture occurred in the lake in order of CO₂ affinity when free CO₂ concentrations dropped below air equilibrium. The results presented here suggest that as atmospheric levels of CO₂ rise, R. raciborskii may become less of a problem to water quality, while some species of chlorophytes may become more dominant. This has implications for stakeholders of many freshwater systems.     

Multigrid Block Preconditioning for a Coupled System of Partial Differential Equations Modeling the Electrical Activity in the Heart

The electrical activity of the heart may be modeled with a system of partial differential equations (PDEs) known as the bidomain model. Computer simulations based on these equations may become a helpful tool to understand the relationship between changes in the electrical field and various heart diseases. Because of the rapid variations in the electrical field, sufficiently accurate simulations require a fine-scale discretization of the equations. For realistic geometries this leads to a large number of grid points and consequently large linear systems to be solved for each time step. In this paper, we present a fully coupled discretization of the bidomain model, leading to a block structured linear system. We take advantage of the block structure to construct an efficient preconditioner for the linear system, by combining multigrid with an operator splitting technique.     

Agricultural Intensification and the Secondary Products Revolution Along the Jordan Rift

The ecological impacts of early agriculture in the Near East remained localized prior to the intensified production of derivative plant and animal products, beginning in the fourth millennium B.C. One aspect of this secondary products revolution (Sherratt, 1980a, 1983) involved the adoption of animal traction and increased production of rendered animal commodities (e.g., wool and dairy). However, most of the pervasive regional effects of this revolution followed from the domestication and increasingly intensive cultivation of orchard crops that generated marketable secondary products (e.g., olive oil, wine, and dried fruits) and encouraged widespread deforestation. In the southern Levant this revolution encouraged, and was encouraged by, the rise and fall of Bronze Age towns and their mercantile influences. Botanical and palynological data from the Jordan Rift reveal a complex discontinuous legacy of changes wrought by the secondary products revolution that have molded the agrarian ecology and anthropogenic landscapes characteristic of the region today.     

Diversion of Anopheles gambiae from children to other hosts following exposure to permethrin-treated bednets

Permethrin-treated bednets reduce mortality and morbidity from malaria in Gambian children. However, it is not certain how this effect is achieved, as neither mosquito numbers nor the human blood index of indoor-resting female Anopheles gambiae Giles sensu lato (Diptera: Culicidae) mosquitoes have been reduced when treated bednets were introduced into a community. One possibility is that insecticide-treated bednets divert mosquitoes from children to adults. To investigate this hypothesis, a cross-over trial with insecticide-treated bednets was undertaken in two small Gambian villages. To differentiate mosquitoes that had fed on children from those that had fed on adults, all children in the study villages were immunized with rabies vaccine before the trial. Using the detection of rabies antibody in a bloodmeal as an indicator that a mosquito had bitten a child, it was found that the percentage of blood-fed mosquitoes caught indoors that had bitten a child fell significantly from 30.8% to 9.2% and from 28.0% to 6.9% in each village after insecticide-treated bednets were introduced. To investigate the possibility that some diversion to animals had occurred, a PCR analysis for human beta-globin DNA was undertaken on selected samples. The results of this investigation were confusing, as some rabies-antibody positive bloodmeals were negative for human DNA. This may have been due to cross-reacting antibodies in animal sera and/or DNA degradation by digestion in the mosquito. Although good evidence for diversion of mosquitoes away from children was obtained, it remains uncertain whether diversion was mainly to adult humans, to animals or to both.     

Immunological responses and viral modulatory effects of vaccination with recombinant modified vaccinia virus Ankara (rMVA) expressing structural and regulatory transgenes of simian immunodeficiency virus (SIVmac32H/J5M)

Background The immunogenicity and protective efficacy of recombinant modified vaccinia virus Ankara (rMVA) vectors expressing structural (gag/pol, env) and regulatory (tat, rev, nef) genes of SIVmac251/32H‐J5 (rMVA‐J5) were assessed. Methods Immunization with rMVA constructs (2.5 × 10⁷ IU) 32, 20 and 8 weeks pre‐challenge was compared with 32 and 20 weeks but with a final boost 8 weeks pre‐challenge with 2 × 10⁶ fixed‐inactivated HSC‐F4 cells infected with SIVmac32H. Controls received rMVA vectors expressing an irrelevant transgene or were naïve challenge controls. All received 10 MID₅₀ SIVmac32H/J5 intravenously. Results Vaccinates immunized with rMVA‐J5 exhibited significant, albeit transient, control of peak primary viraemia despite inconsistent and variable immune responses elicted by vaccination. Humoral and cellular responses to Env were most consistent, with lower responses to Nef, Rev and Tat. Increasing titres of anti‐vaccinia neutralizing antibodies reflected the number and dose of rMVA inoculations. Conclusions Improved combinations of viral vectors are required to elicit appropriate immune responses to control viral replication.