Aceitação e preferência de frutos para oviposição em duas populações de Ceratitis capitata (Diptera, Tephritidae)

The influence of four host fruits, orange (Citrus sinensis L.), papaya (Carica papaya L.), mango (Mangifera indica L.) and apple (Malus domestica Borkh) on oviposition behavior of Ceratitis capitata (Wiedemann, 1824) was evaluated. Experiments were carried out on two C. capitata laboratory-reared populations: one with artificial diet for 10 years with periodic introduction of wild flies and other reared with artificial diet for 20 years without wild flies introduction. In acceptance experiments two pieces of a single fruit type were exposed to a group of 10 females; after 48 hours, these were changed by two new pieces of the same fruit type, and, in the end of the fourth day, the experiments were concluded. In preference experiments, two pieces of different fruits were offered to the females. These experiments were driven under the same conditions of the acceptance ones. Acceptance and preference experiments for both populations showed the following choice hierarchy: papaya > mango > orange > apple. The acceptance experiments showed no differences in the number of eggs/female/day laid in the first 48 hours and in the last 48 hours of the experiments. The amount of eggs in the two pieces of fruits offered to the females was similar. In spite of the two populations present similar behavior in relation to host hierarchy, the number of laid eggs was different, being larger for the population reared without wild flies introduction.

Cross-infection experiments with "isospora" of cats and dogs

Feces of 34 dogs out of 251 (13.5%) from guanabara were positive for Isospora. From these 19 (7.5%) were i. rivolta, 13 (5.2%) were I. canis and 2 (0,7) were i. bigemina. "Free-sporocysts" of I. rivolta were eliminated by 9 dogs (3.5%). A "Caryospora-like" oocyst was seen once. Cross-infection experiments performed with Isospora from dogs and cats failed to produce infection while inoculations of these Isospora in their natural hosts succeeded. The results suggest that the species of Isospora occurring in cats are different from those of dogs.

Further experiments on susceptibility of Biomphalaria amazonica to Schistosoma mansoni

A sample of Biomphalaria amazonica from Porto Velho, Rondônia state, was exposed to miracidia of Schistosoma mansoni (SJ2 strain) from São José dos Campos, São Paulo state (five miracidia per snail). Water freshly taken from the snails' breeding place was used to make sure that its quality was compatible with hatching of miracidia and their penetration into the snails. The resulting infection rate was 3.5%, as against 45% in B. tenagophila controls. In comparison with the controls, B. amazonica, besides a lower infection rate, showed a longer prepatent period and a lower cercarial production. These characteristics seem to indicate that it is a poor host of S. mansoni, like B. straminea, but it should be considered that, this notwithstanding, the latter is admittedly a good vector of the parasite in hyperendemic areas of northeastern Brazil. These results point to the possibility of introduction of schistosomiasis mansoni into the western Amazonian region, where B. amazonica is widespread.

Anesthesia of Biomphalaria spp. (Mollusca, Gastropoda): sodium pentobarbital is the drug of choice

The anesthetic effect of some water-soluble anesthesic or narcotic drugs currently used in mice was tested in molluscs of the Biomphalaria genus. Sodium thiopental was very toxic to the snails resulting in high rates of mortality in all the treatment schedules tested. Cetamine base, at concentration of 0.25 mg/ml of water, resulted in partial snail anesthesia (40% of snails were anesthetized) only after 20 h of exposition. The association of Cetamine base with Tiazine chloridrate did not improve the anesthesic effect, and higher concentrations of these drugs were toxic to the snails. Sodium pentobarbital at 0.4 mg/ml in water for 8 h was the best treatment schedule to anesthetize Biomphalaria snails. In this schedule, the snails were anesthetized without any toxic effect. The procedure provides a powerful tool for in vivo studies that demande a complete state of snail anesthesia.

Interaction between the Intermediate Host of Schistosomiasis in Brazil Biomphalaria glabrata (Planorbidae) and a Possible Competitor Melanoides tuberculata (Thiaridae): I. Laboratory Experiments

The biological control of Biomphalaria glabrata, intermediate host of Schistosoma mansoni, is one the accepted options to fight schistosomiasis. One of the most promising candidates to control B. glabrata is the snail Melanoides tuberculata, a potential competitor. However, the mechanisms of interaction between the two species are not clear. Our objective is to determine if M. tuberculata indeed compete with B. glabrata, using two laboratory experiments. In Experiment 1, we tested the effect of the presence of M. tuberculata on the fecundity and mortality rates of B. glabrata. In Experiment 2, we tested if there was a direct or indirect interaction between the two species. In Experiment 1, M. tuberculata was eliminated after the peak in reproductive activity of B. glabrata. In Experiment 2, B. glabrata produced more egg masses when raised with M. tuberculata. The conditions leading to this unexpected positive effect of M. tuberculata on the fecundity of B. glabrata need further clarification, but emphasize that detailed studies of the interaction between these species in the conditions of the local environment should be considered.

Variation of the Oviposition Preferences of Aedes aegypti in Function of Substratum and Humidity

Two Aedes aegypti (L.) populations were studied in the laboratory regarding the preference for three types of breeding sites, i.e., flasks containing only water, flasks with a plant and flasks with a stick. Each of these breeding units was placed in one cage and the choice of the oviposition sites was determined for individual females and three females per experimental unit at two humidity levels. Preference for ovipositing on the water surface was observed and varied according to experimental unit and humidity. Mean hatching of eggs in water surface was 46.6%. Experiments with three females showed a more marked difference than when only one female was used. Inter and intrapopulation variability regarding oviposition sites was observed. The discrimination between the different oviposition substrates, hatching in water surface and its implication for mosquito control are discussed.

An Adenovirus Vector Containing the Suicide Gene Thymidine Kinase for a Broad Application in Cancer Gene Therapy

Treatment of cancer using gene therapy is based on adding a property to the cell leading to its elimination. One possibility is the use of suicide genes that code for enzymes that transform a pro-drug into a cytotoxic product. The most extensively used is the herpes simplex virus thymidine kinase (TK) gene, followed by administration of the antiviral drug ganciclovir (GCV). The choice of the promoter to drive the transcription of a transgene is one of the determinants of a given transfer vector usefulness, as different promoters show different efficiencies depending on the target cell type. In the experiments presented here, we report the construction of a recombinant adenovirus carrying TK gene (Ad-TK) driven by three strong promoters (P CMV IE, SV40 and EN1) and its effectiveness in two cell types. Human HeLa and mouse CCR2 tumor cells were transduced with Ad-TK and efficiently killed after addition of GCV. We could detect two sizes of transcripts of TK gene, one derived from the close together P CMV IE/SV40 promoters and the other from the 1.5 Kb downstream EN1 promoter. The relative amounts of these transcripts were different in each cell type thus indicating a higher flexibility of this system.

Crossing experiments detect genetic incompatibility among populations of Triatoma brasiliensis Neiva, 1911 (Heteroptera, Reduviidae, Triatominae)

Triatoma brasiliensis is composed of at least four geographic populations (brasiliensis, melanica, macromelasoma, and juazeiro) that have distinct chromatic, morphologic, biologic and ecologic patterns, and genetic composition. Reciprocal crosses between all pairwise combinations were carried out in order to evaluate the genetic and reproductive compatibility of these four populations. The F1 individuals developed normally and the resulting adults were crossed again to test the F2 and F3 viability. Genetic incompatibility was found between melanica and brasiliensis populations.

Are vectors able to learn about their hosts? A case study with Aedes aegypti mosquitoes

The way in which vectors distribute themselves amongst their hosts has important epidemiological consequences. While the role played by active host choice is largely unquestioned, current knowledge relates mostly to the innate response of vectors towards stimuli signalling the presence or quality of their hosts. Many of those cues, however, can be unpredictable, and therefore prevent the incorporation of the appropriate response into the vector's behavioural repertoire unless some sort of associative learning is possible. We performed a wide range of laboratory experiments to test the learning abilities of the mosquito, Aedes aegypti. Mosquitoes were exposed to choice procedures in (1) an olfactomenter and (2) a 'visual arena'. Our goal was to determine whether the mosquitoes were able to associate unconditional stimuli (blood feeding, human breath, vibration and electrical shock) with particular odours (citral, carvone, citronella oil and eugenol) and visual patterns (horizontal or vertical black bars) to which they had been previously observed to be responsive. We found no evidence supporting the hypothesis that associative learning abilities are present in adult Ae. aegypti. We discuss the possibilities that the assays employed were either inappropriate or insufficient to detect associative learning, or that associative learning is not possible in this species.

Trypanosoma cruzi strains isolated from human, vector, and animal reservoir in the same endemic region in Mexico and typed as T. cruzi I, discrete typing unit 1 exhibit considerable biological diversity

In this study, three strains of Trypanosoma cruzi were isolated at the same time and in the same endemic region in Mexico from a human patient with chronic chagasic cardiomyopathy (RyC-H); vector (Triatoma barberi) (RyC-V); and rodent reservoir (Peromyscus peromyscus) (RyC-R). The three strains were characterized by multilocus enzyme electrophoresis, random amplified polymorphic DNA, and by pathological profiles in experimental animals (biodemes). Based on the analysis of genetic markers the three parasite strains were typed as belonging to T. cruzi I major group, discrete typing unit 1. The pathological profile of RyC-H and RyC-V strains indicated medium virulence and low mortality and, accordingly, the strains should be considered as belonging to biodeme Type III. On the other hand, the parasites from RyC-R strain induced more severe inflammatory processes and high mortality (> 40%) and were considered as belonging to biodeme Type II. The relationship between genotypes and biological characteristics in T. cruzi strains is still debated and not clearly understood. An expert committee recommended in 1999 that Biodeme Type III would correspond to T. cruzi I group, whereas Biodeme Type II, to T. cruzi II group. Our findings suggest that, at least for Mexican isolates, this correlation does not stand and that biological characteristics such as pathogenicity and virulence could be determined by factors different from those identified in the genotypic characterization

Malaria diagnosis from pooled blood samples: comparative analysis of real-time PCR, nested PCR and immunoassay as a platform for the molecular and serological diagnosis of malaria on a large-scale

Malaria diagnoses has traditionally been made using thick blood smears, but more sensitive and faster techniques are required to process large numbers of samples in clinical and epidemiological studies and in blood donor screening. Here, we evaluated molecular and serological tools to build a screening platform for pooled samples aimed at reducing both the time and the cost of these diagnoses. Positive and negative samples were analysed in individual and pooled experiments using real-time polymerase chain reaction (PCR), nested PCR and an immunochromatographic test. For the individual tests, 46/49 samples were positive by real-time PCR, 46/49 were positive by nested PCR and 32/46 were positive by immunochromatographic test. For the assays performed using pooled samples, 13/15 samples were positive by real-time PCR and nested PCR and 11/15 were positive by immunochromatographic test. These molecular methods demonstrated sensitivity and specificity for both the individual and pooled samples. Due to the advantages of the real-time PCR, such as the fast processing and the closed system, this method should be indicated as the first choice for use in large-scale diagnosis and the nested PCR should be used for species differentiation. However, additional field isolates should be tested to confirm the results achieved using cultured parasites and the serological test should only be adopted as a complementary method for malaria diagnosis.

Understanding the hierarchy governance choice of some wineries in Brazil - case study of 3 Brazilian wineries

ABSTRACT This study aims to contribute towards understanding the multiple factors, which influence firm's governance decisions. To identify some of these factors, three cases in the Brazilian wine industry were analyzed: Miolo located in Vale dos Vinhedos (South of Brazil) and in Vale do Rio São Francisco (Northeast of Brazil); Don Laurindo located in Vale dos Vinhedos; and ViniBrasil located in Vale do Rio São Francisco. For the most part, all three firms procure the grapes they use for their wine production in-house. Only Miolo purchases an insignificant amount of grapes outside of its production. By Brazilian standards, these regions have a long tradition of grape production and it is not difficult to purchase sufficient quantity of grapes to produce wine. However, the wineries are concerned also about the quality of the grapes they use and purchasing high-quality grapes might be critical issue. On the other hand, the quality of grapes is easily measured and the cost to buy in the market is cheaper than producing in-house. Furthermore, also the level of asset specificity present in the grape-grower-wine-producer transaction seems, by itself, insufficient to justify the use of hierarchical governance forms. Then, the aim of the article is to analyze the reasons why these wineries largely rely on hierarchy governance forms to procure their grape-inputs. What explains their use of hierarchy governance, given that both asset specificity and measurement problems appear to be relatively low?

Information overload, choice deferral, and moderating role of need for cognition: Empirical evidence

ABSTRACT Choice deferral due to information overload is an undesirable result of competitive environments. The neoclassical maximization models predict that choice avoidance will not increase as more information is offered to consumers. The theories developed in the consumer behavior field predict that some properties of the environment may lead to behavioral effects and an increase in choice avoidance due to information overload. Based on stimuli generated experimentally and tested among 1,000 consumers, this empirical research provides evidence for the presence of behavioral effects due to information overload and reveals the different effects of increasing the number of options or the number of attributes. This study also finds that the need for cognition moderates these behavioral effects, and it proposes psychological processes that may trigger the effects observed.

Study of the combined radial post-feeding dispersion of the blowflies Chrysomya megacephala (Fabricius) and C. albiceps (Wiedemann) (Diptera, Calliphoridae)

Blowflies use discrete and ephemeral substrates to feed their larvae. After they run out of food, the larvae begin to disperse in order to find adequate places for pupation or additional food sources, a process named post-feeding larval dispersion. Some important aspects of this process were studied in a circular arena allowing the combined radial post-feeding dispersion from the center of the arena of C. albiceps and C. megacephala larvae. To determine the location of each pupa, the arena was divided in 72 identical sections starting from the center. The distance from the center, the depth and weight of each pupa were evaluated. Statistical tests were done to verify the relation between weight, depth and distance for pupation. From the total an average of 976 larvae released (488 for each species) were collected considering both experiments 456 C. megacephala pupae and 488 of C. albiceps. This demonstrates that C. albiceps probably preyed on 32 C. megacephala larvae during post-feeding dispersion. The study of this dispersion process can be used to estimate the postmortem interval (PMI) of human cadavers in legal medicine.