Molecular biological approaches to the study of vectors in relation to malaria control

To a large extent, control of malaria vectors relies on the elimination of breeding sites and the application of chemical agents. There are increasing problems associated with the use of synthetic insecticides for vector control, including the evolution of resistance, the high cost of developing and registering new insecticides and an awareness of pollution from insecticide residues. These factors have stimulated interest in the application of molecular biology to the study of mosquito vectors of malaria; focussing primarily on two aspects. First, the improvement of existing control measures through the development of simplified DNA probe systems suitable for identification of vectors of malaria. The development of synthetic, non-radioactive DNA probes suitable for identification of species in the Anopheles gambiae complex is described with the aim of defining a simplified methodology wich is suitable for entomologist in the field. The second aspect to be considered is the development of completely novel strategies through the development of completely novel strategies through the genetic manipulation of insect vectors of malaria in order to alter their ability to transmit the disease. The major requirements for producing transgenic mosquitoes are outlined together with the progress wich has been made to date and discussed in relation to the prospects which this type of approach has for the future control of malaria.

Endogenous steroid profiling in the athlete biological passport.

The Athlete Biological Passport (ABP) is an individual electronic document that collects data regarding a specific athlete that is useful in differentiating between natural physiologic variations of selected biomarkers and deviations caused by artificial manipulations. A subsidiary of the endocrine module of the ABP, that which here is called Athlete Steroidal Passport (ASP), collects data on markers of an altered metabolism of endogenous steroidal hormones measured in urine samples. The ASP aims to identify not only doping with anabolic-androgenic steroids, but also most indirect steroid doping strategies such as doping with estrogen receptor antagonists and aromatase inhibitors. Development of specific markers of steroid doping, use of the athlete's previous measurements to define individual limits, with the athlete becoming his or her own reference, the inclusion of heterogeneous factors such as the UDPglucuronosyltransferase B17 genotype of the athlete, the knowledge of potentially confounding effects such as heavy alcohol consumption, the development of an external quality control system to control analytical uncertainty, and finally the use of Bayesian inferential methods to evaluate the value of indirect evidence have made the ASP a valuable alternative to deter steroid doping in elite sports. The ASP can be used to target athletes for gas chromatography/combustion/ isotope ratio mass spectrometry (GC/C/IRMS) testing, to withdraw temporarily the athlete from competing when an abnormality has been detected, and ultimately to lead to an antidoping infraction if that abnormality cannot be explained by a medical condition. Although the ASP has been developed primarily to ensure fairness in elite sports, its application in endocrinology for clinical purposes is straightforward in an evidence-based medicine paradigm.

Molecular mechanisms and biological importance of Plasmodium falciparum erythrocyte rosetting

Rosetting, i.e. the spontaneous binding of uninfected to malaria infected erythrocytes and endothelial cytoadherence may hinder the blood flow and lead to serve Plasmodium falciparum malaria. Falciparum isolates obtained from unconscious patients all form rosettes and/or express a significantly higher man rosetting rate than isolates from patients with uncomplicated malaria. Furthermore, sera of patients with cerebral malaria are devoid of anti-rosetting activity while sera from patients with mild disease carry high levels of anti-rosetting antibodies. The presence of anti-rosetting antibodies also seems important for the efficient interaction of rosetting infected rbc and leucocytes. Two parasite derived rosetting ligands of Mr 22k and Mr28K named "rosettins, have been found on the surface of rosetting infected erythrocytes. CD36 has in at least some strains of parasites been found to function as a rosetting receptor on the uninfectederythrocyte. Heparin disrupts rosettes of P. falciparum in vitro and inhibits the sequestration of rosetting cells ex vivo. In conclusion, rosetting seems a crucial factor in the development of cerebral malaria and treatment of patients with anti-rosetting substances might become an effectivew adjunct in the treatment of severe malaria.

Sialoglycoconjugates in Trypanosoma cruzi-host cell interaction: possible biological model - a review

A number of glycoconjugates, including glycolipids and glycoproteins, participate in the process of host-cell invasion by Trypanosoma cruzi and one of the most important carbohydrates involved on this interaction is sialic acid. It is known that parasite trans-sialidase participates with sialic acid in a coordinated fashion in the initial stages of invasion. Given the importance of these sialogycoconjugates, this review sets out various possible biological models for the interaction between the parasite and mammalian cells that possess a sialylated receptor/ligand system.

The Crocidura fuliginosa species complex (Mammalia, Insectivora) in Peninsular Malaya: biological, karyological and genetical evidence

Four West Malaysian shrew populations of the genus Crocidura were investigated through their karyotype and allozyme variations, and, in part, by interfertility experiments. Two different karyotypes characterize these shrews. The first, restricted to the Cameron Highlands (Peninsular Malaysia), invariably has 2n = 40 chromosomes but a varying fundamental number (FN = 54-58). The second karyotype shows a fundamental number of 62-68 and a polymorphic chromosomal number of 2n = 38, 39 or 40, a rare event in the genus Crocidura. Thus both can be distinguished by either a low or a higher number of meta- and submetacentric elements. In heterospecific breeding experiments, mutual avoidance was observed suggesting prezygotic barriers, whereas intraspecific pairs produced 13 liters (mean 2.1 young). Furthermore, our biochemical results indicate that both karyotypes correspond to a relatively ancient separation (Nei's D = 0.354), an amount of genetic differentiation comparable to the distance separating them from the West Palearctic C. russula (D = 0.429-0.583). In contrast, conspecific island and mainland Malaysian shrews possessing the second karyotype had only one fixed allelic difference over the 35 loci surveyed. The problem of naming the two biological species remains unsolved and requires further comparative investigations.

A novel merozoite surface antigen of Plasmodium falciparum (MSP-3) identified by cellular-antibody cooperative mechanism antigenicity and biological activity of antibodies

We report the identification of a 48kDa antigen targeted by antibodies which inhibit Plasmodium falciparum in vitro growth by cooperation with blood monocytes in an ADCI assay correlated to the naturally acquired protection. This protein is located on the surface of the merozoite stage of P. falciparum, and is detectable in all isolates tested. Epidemiological studies demonstrated that peptides derived from the amino acid sequence of MSP-3 contain potent B and T-cell epitopes recognized by a majority of individuals living in endemic areas. Moreover human antibodies either purified on the recombinant protein, or on the synthetic peptide MSP-3b, as well as antibodies raised in mice, were all found to promote parasite killing mediated by monocytes.

Some environmental and biological factors influencing the activity of entomopathogenic Bacillus on mosquito larvae in Brazil

The influence of environmental and biological factors on the efficacy of Bacillus thuringiensis serovar israelensis and B. sphaericus as mosquito larvicides are reviewed. The importance of strain dependence, cultivating media/methods, mosquito species/specificity, formulations and their relation to mosquito feeding habits, as well as temperature, solar exposure, larval density and concomitant presence of other aquatic organisms are addressed with reference to the present status of knowledge in Brazil.

Biological control program against simuliids in the State of São Paulo, Brazil

In Brazil, the use of biological vector-control methods has been largely confined to experimental research, with little or no application of such techniques by public institutions responsible for implementing control programs. The notable exceptions have been the black fly control program carried out by the Health Secretariat in the State of São Paulo. Since the 1980s, São Paulo's "Superintendência de Controle de Endemias" has been conducting studies on the viability of using Bacillus thuringiensis (H-14) for simuliid control, and the results have been so encouraging that the agency has now incorporated this method into its Simuliid Control Program.

Ecologia de les Invasions Ecològiques

La paradoxa de les invasions planteja com és possible que algunes espècies siguin capaces d'envair regions a les que no han evolucionat i, fins i tot, arribar a ser més abundants que espècies autòctones que han tingut més oportunitat d’adaptars’hi. Comprendre l’ecologia de les invasions és especialment interessant perquè algunes d’aquestes espècies causen greus impactes ecològics i econòmics arreu del món. Per intentar resoldre la paradoxa en aquest treball s’ha seguit dues aproximacions. Per una banda, mitjançant anàlisis comparatius s’ha volgut identificar aquelles característiques que afecten el resultat de les introduccions d’ocells, i utilitzar-les com a predictors en protocols d’avaluació de riscos per prevenir futures invasions. Seguint en aquest nivell d’aproximació també s’ha volgut validar si, tal com prediu la teoria ecològica, les estratègies vitals de les espècies afecten l'èxit en l'establiment de poblacions d'ocells exòtics. D'altra banda, a través d'aproximacions descriptives i experimentals, s’ha volgut investigar els mecanismes d’invasió en un cas d’estudi concret, el del Rossinyol del Japó (Leiothrix lutea) als boscos de Collserola (Barcelona). Els anàlisis comparatius han mostrat que és possible de predir la probabilitat d’establiment de les espècies introduïdes a partir d’unes poques característiques amb notable precisió. Altrament, l’anàlisi sobre l’efecte de les estratègies vitals sobre el resultat de les invasions sembla indicar que hi ha un biaix en el registre històric d’introduccions que impedeix descobrir la naturalesa d’aquesta relació i suggereixen buscar una aproximació alternativa per al problema. Respecte el cas del Rossinyol del Japó, els resultats preliminars suggereixen que les raons del seu èxit als boscos de Collserola podrien ser que ha trobat un nínxol ecològic que està poc aprofitat per les espècies natives. Aquest treball vol mostrar com a través de la integració de diferents aproximacions podem ser capaços d’aportar una visió més completa per comprendre la paradoxa de les invasions.

Biological comparison between three clones of Trypanosoma cruzi and the strain of origin (Bolivia) with reference to clonal evolution studies

After isolating three clones of Trypanasoma cruzi (Bolivia), we first characterized them according to parasitaemia, pleomorphism and virulence, and then histopathologically. The study's interest lies on the hypothesis that clonal evolution of T. cruzi has a major impact on biologically relevant properties of this parasite. Data obtained from the studies of parasitaemia, pleomorphism and virulence showed no differences between the groups studied. As a final point, the histopathological study shows us a muscular tissue tropism both in clones and in their mother strain (Bolivia). In this paper, we conclude that Bolivia strain and clones isolated from it, pertaining to the same major clone share similar biological properties.

Biological variation in Anopheles darlingi root

Behavioural variation in the South American malaria vector Anopheles darlingi is described. At the centre of its distribution, in forest areas close to the city of Manaus, Brazil, it is primarily exophagic and exophilic. Mosquitoes from this area are chromosomally diverse. Towards the northern edge of its distribution (in Guyana and Venezuela) it is more endophagic and less diverse chromosomally. Similarly in the south (in the state of Minas Gerais) it is less polymorphic. In this area, however, it is primarily zoophilic and exophagic. Evidence is presented that female wing size may vary between populations. The possibility that this widely distributed species may be a complex could have important implications for future malaria control schemes.

Biological characterization of clones derived from the edmonston strain of measles virus in comparison with schwarz and CAM-70 vaccine strains

Four virus clones were derived from the Edmonston strain of measles virus by repeated plaque purification. These clones were compared with the vaccine strains Schwarz and CAM-70 in terms of biological activities including plaque formation, hemagglutination, hemolysis and replication in Vero cells and chick embryo fibroblasts (CEF). Two clones of intermediate plaque yielded mixed plaque populations on subcultivation whereas the other two, showing small and large plaque sizes, showed stable plaque phenotypes. The vaccine strains showed consistent homogeneous plaque populations. All the Edmonston clones showed agglutination of monkey erythrocytes in isotonic solution while both vaccine strains hemagglutinated only in the presence of high salt concentrations. Variation in the hemolytic activity was observed among the four clones but no hemolytic activity was detected for the vaccine virus strains. Vaccine strains replicated efficiently both in Vero cells and CEF. All four clones showed efficient replication in Vero cells but different replication profiles in CEF. Two of them replicated efficiently, one was of intermediate efficiency and the other showed no replication in CEF. Two of the clones showed characteristics similar to vaccine strains. One in terms of size and homogeneity of plaques, the other for a low hemolytic activity and both for the efficiency of propagation in CEF.

Characterization and biological activity of a brazilian isolate of Bacillus sphaericus (Neide) highly toxic to mosquito larvae

Primary powders of Bacillus sphaericus strain S2 isolated from soil samples in Brazil, and strain 2362 were produced in a 14 liter fermentor. Growth patterns and sporulation observed in three trials with strains S2 and 2362 in the fermentor were similar. Second-instar larvae of Culex quinquefasciatus, Anopheles albimanus, Anopheles quadrimaculatus, and Aedes aegypti exposed for 48 hr to strain S2 responded with LC50 values of 0.25, 5.95, 12.28 and 140.0 ppb of lyophilized primary powder, respectively. Under the same conditions, strain 2362 resulted in LC50 values of 0.39, 7.16, 16.93 and 307.0 ppb of lyophilized primary powder, respectively, in those mosquito larvae. Statistical analysis of the bioassay data did not show significant differences among LC50 values observed in B. sphaericus strains S2 and 2362, at the 0.05 level. Toxins of strains S2 and 2362 were extracted at pH 12 with NaOH. Electrophoresis of the extracts in polyacrylamide gel under denaturing conditions revealed the 51 and 42 kDa toxins in both S2 and 2362 B. sphaericus strains. The presence of the 42 kDa peptide in the extracts was confirmed by Western blot and Elisa, with anti-42 kDa IgG previously prepared from strain 2362.