Existence of a sex pheromone in Triatoma infestans (Hemiptera: Reduvidae): II. Electrophysiological correlates

The stimulus provided by a copulating pair of Triatoma infestans significantly affects the electrical activity of the nervous system of Triatoma infestans. Electrophysiological recordings were perfomed on stationary adult males presented with stimuli of an air current carrying odors from males, females, non-copulating pairs and mating pairs. The electrophysiological response was characterized by the low frequency occurrence of biphasic compound impulses. A significant increase in the frequency of the impulses occurred in stationary males when exposed to air currents of mating pairs, when compared to that evoked by a clean air stream. Analysis of the time course of the assays, showed that the electrophisiological activity during the copula was higher than prior to or after copula. The electrophysiological evidence presented here strongly supports the existence of pheromone(s) released by one or both sexes during mating and which is perceived by male chemoreceptors located on the antennae.

Analysis of a finite volume element method for the Stokes problem

In this paper we propose a stabilized conforming finite volume element method for the Stokes equations. On stating the convergence of the method, optimal a priori error estimates in different norms are obtained by establishing the adequate connection between the finite volume and stabilized finite element formulations. A superconvergence result is also derived by using a postprocessing projection method. In particular, the stabilization of the continuous lowest equal order pair finite volume element discretization is achieved by enriching the velocity space with local functions that do not necessarily vanish on the element boundaries. Finally, some numerical experiments that confirm the predicted behavior of the method are provided.

Mating system and avpr1a promoter variation in primates.

It has been suggested that primate mating and social behaviours may be influenced by variation in promoter region repetitive DNA of the vasopressin receptor 1a gene (avpr1a). We show that male mating behaviour does not covary in a simple way with promoter repetitive DNA in 12 Old World primates. We found that one microsatellite (-553 bp upstream) was present in all species, irrespective of their behaviour. By contrast, two microsatellites (-3956 and -3625 bp upstream) were present only in some species, yet this variation did not correlate with behaviour. These findings agree with a recent comparative analysis of voles and show that the variation in repetitive DNA in the avpr1a promoter region does not generally explain variation in male mating behaviour. Phylogenetic analysis revealed a GAGTA motif that has been independently deleted three times and involved in another larger deletion. Importantly, the presence/absence of this GAGTA motif leads to changes in predicted transcription factor-binding sites. Given the repeated loss of this motif, we speculate that it might be of functional relevance. We suggest that such non-repetitive variation, either in indels or in sequence variation, are likely to be important in explaining interspecific variation in avpr1a expression.

A low stringency polymerase chain reaction approach to the identification of Biomphalaria glabrata and B. tenagophila, intermediate snail hosts of Schistosoma mansoni in Brazil

The low stringency-polymerase chain reaction (LS-PCR) with a pair of specific primers for the amplification of the 18S rRNA gene was evaluated as a means of differentiating between the two Schistosoma mansoni intermediate host species in Brazil: Biomphalaria glabrata and B. tenagophila. Individual snails obtained from different states of Brazil were used and the amplification patterns obtained showed a high degree of genetic variability in these species. Nevertheless, 4 and 3 clearly defined specific diagnostic bands was observed in individuals from B. glabrata and B. tenagophila respectively. The detection of snail specific diagnostic bands suggests the possibility of reliable species differentiation at the DNA level using LS-PCR.

Bioinformática: identificar genes en una interfaz gráfica vía web para la comparación de genomas

Este trabajo desarrolla el proceso de diseño e implementación de una interfaz web que permite la exploración en detalle de las relaciones entre genomas completos. La interfaz permite la comparación simultánea de nueve genomas, representando en cada gráfica las relaciones entre cada par de genomas junto los genes identificados de cada uno de ellos. Es capaz de trabajar con genomas del dominio Eukaryota y se adapta a la capacidad de cómputo de la máquina cliente. La información representada son MUMs (Maximal Unique Matching, secuencia máxima y única encontrada en ambos genomas) y SuperMUMs (agrupación de MUMs mediante Approximate String Matching). Los datos son previamente calculados y accesibles desde un servidor web.

FtsK Is a DNA motor protein that activates chromosome dimer resolution by switching the catalytic state of the XerC and XerD recombinases.

FtsK acts at the bacterial division septum to couple chromosome segregation with cell division. We demonstrate that a truncated FtsK derivative, FtsK(50C), uses ATP hydrolysis to translocate along duplex DNA as a multimer in vitro, consistent with FtsK having an in vivo role in pumping DNA through the closing division septum. FtsK(50C) also promotes a complete Xer recombination reaction between dif sites by switching the state of activity of the XerCD recombinases so that XerD makes the first pair of strand exchanges to form Holliday junctions that are then resolved by XerC. The reaction between directly repeated dif sites in circular DNA leads to the formation of uncatenated circles and is equivalent to the formation of chromosome monomers from dimers.

Specific Identification of Biomphalaria tenagophila and Biomphalaria occidentalis Populations by the Low Stringency Polymerase Chain Reaction

Although Biomphalaria occidentalis and B. tenagophila are indistinguishable on the basis of shell morphology and the majority of their genital organs, only the latter is susceptible to infection with Schistosoma mansoni. Thus, the identification of these species is fundamental to epidemiological studies of schistosomiasis. Here we describe a simple and rapid method for differentiating B. tenagophila from B. occidentalis based on low stringency polymerase chain reaction and using a pair of primers specific for the amplification of the 18S rRNA gene. Analysis of the low stringency product profiles of populations of these snails from different geographical regions confirmed this approach as being applicable to the identification of B. tenagophila and B. occidentalis in cases where classical morphology is inconclusive

Morphology and Histology of the Female Reproductive System of Abedus ovatus Stal (Belostomatidae: Hemiptera: Insecta)

In Abedus ovatus Stal, the female reproductive system consists of a pair of ovaries leading to oviduct and opens out by genital aperture. Each ovary is composed of five telotrophic ovarioles, with four different regions, terminal filament, germarium, vitellarium and pedicel. Germarium and vitellarium are the germ tubes in which the development of oocyte occurs. In the germarium, the differentiation of trophocytes into young oocytes was observed in three zones, ZI, ZII and ZIII. Further development of oocytes in the vitellarium could be divided into seven stages, STI STVII. The developed eggs are lodged in the pedicel

A Simple Reverse Transcription-Polymerase Chain Reaction for Dengue Type 2 Virus Identification

We show here a simplified reverse transcription-polymerase chain reaction (RT-PCR) for identification of dengue type 2 virus. Three dengue type 2 virus strains, isolated from Brazilian patients, and yellow fever vaccine 17DD, as a negative control, were used in this study. C6/36 cells were infected with the virus, and tissue culture fluids were collected after 7 days of infection period. The RT-PCR, a combination of RT and PCR done after a single addition of reagents in a single reaction vessel was carried out following a digestion of virus with 1% Nonidet P-40. The 50ml assay reaction mixture included 50 pmol of a dengue type 2 specific primer pair amplifying a 210 base pair sequence of the envelope protein gene, 0.1 mM of the four deoxynucleoside triphosphates, 7.5U of reverse transcriptase, and 1U of thermostable Taq DNA polymerase. The reagent mixture was incubated for 15 min at 37oC for RT followed by a variable amount of cycles of two-step PCR amplification (92oC for 60 sec, 53oC for 60 sec) with slow temperature increment. The PCR products were subjected to 1.7% agarose gel electrophoresis and visualized with UV light after gel incubation in ethidium bromide solution. DNA bands were observed after 25 and 30 cycles of PCR. Virus amount as low as 102.8 TCID50/ml was detected by RT-PCR. Specific DNA amplification was observed with the three dengue type 2 strains. This assay has advantages compared to other RT-PCRs: it avoids laborious extraction of virus RNA; the combination of RT and PCR reduces assay time, facilitates the performance and reduces risk of contamination; the two-step PCR cycle produces a clear DNA amplification, saves assay time and simplifies the technique

Peripheral T-cell lymphoma with t(6;14)(p25;q11.2) translocation presenting with massive splenomegaly.

Recurrent chromosomal translocations associated to peripheral T-cell lymphomas (PTCL) are rare. Here, we report a case of PTCL, not otherwise specified (NOS) with the karyotype 46,Y,add(X)(p22),t(6;14)(p25;q11) and FISH-proved breakpoints in the IRF4 and TCRAD loci, leading to juxtaposition of both genes. A 64-year-old male patient presented with mild cytopenias and massive splenomegaly. Splenectomy showed diffuse red pulp involvement by a pleomorphic medium- to large-cell T-cell lymphoma with a CD2+ CD3+ CD5- CD7- CD4+ CD8+/- CD30- TCRbeta-F1+ immunophenotype, an activated cytotoxic profile, and strong MUM1 expression. The clinical course was marked by disease progression in the bone marrow under treatment and death at 4 months. In contrast with two t(6;14)(p25;q11.2)-positive lymphomas previously reported to be cytotoxic PTCL, NOS with bone marrow and skin involvement, this case was manifested by massive splenomegaly, expanding the clinical spectrum of PTCLs harboring t(6;14)(p25;q11.2) and supporting consideration of this translocation as a marker of biological aggressiveness.

Ultrastructure of Endogenous Stages of Eimeria ninakohlyakimovae Yakimoff & Rastegaieff, 1930 Emend. Levine, 1961 in Experimentally Infected Goat

The ultrastructure of endogenous stages of Eimeria ninakohlyakimovae was observed in epithelial cells of cecum and colon crypts from a goat experimentally infected with 2.0 x 105 oocysts/kg. The secondary meronts developed above the nucleus of the host cell. The nucleus first divides and merozoites then form on the surface of multinucleated meronts. Free merozoites in the parasitophorous vacuole present a conoid, double membrane, one pair of rhoptries, micronemes, micropore, anterior and posterior polar ring, a nucleus with a nucleolus and peripheral chromatin. The microgamonts are located below the nucleus of the host cell and contain several nuclei at the periphery of the parasite. The microgametes consist of a body, a nucleus, three flagella and mitochondria. The macrogamonts develop below the nucleus of the host cell and have a large nucleus with a prominent nucleolus. The macrogametes contain a nucleus, wall-forming bodies of type I and type II. The young oocysts present a wall containing two layers and a sporont

Habitat, breeding performance, diet and individual age in Swiss barn owls (Tyto alba)

Intensification of farming over the past 50 years has homogenised the landscape structure and contributed to the decline of bird populations in Europe. To better target the conservation of the Barn Owl Tyto alba, we assessed the influence of the landscape structure on breeding performance in western Switzerland. The analyses considered a 23-year data set of breeding parameters collected in an area dominated by intensive agriculture. Using a Geographic Information System approach, landscape characteristics were described around 194 nest sites. Our analyses showed that nest-box occupancy, laying date, clutch and brood size, egg volume and probability of producing a second annual clutch were not significantly associated with any of the eight principal landscape variables (agricultural land, woodland, urban area, hedgerows, cereals, sugar beet, maize and meadow). Nevertheless, the probability that a breeding pair occupied a nest-box decreased the more roads there were surrounding the nest-box. The absence of strong associations between habitat features and breeding parameters suggests that prey availability may be relatively similar between the different breeding sites. In our study area Barn Owls can always find suitable foraging habitats around most nest-boxes.

Proceedings of the Schistosome Genome Project

"The host-parasite relationship" is a vast and diverse research field which, despite huge human and financial input over many years, remains largely shrouded in mystery. Clearly, the adaptation of parasites to their different host species, and to the different environmental stresses that they represent, depends on interactions with, and responses to, various molecules of host and/or parasite origin. The schistosome genome project is a primary strategy to reach the goal; this systematic research project has successfully developed novel technologies for qualitative and quantitative characterization of schistosome genes and genome organization by extensive international collaboration between top quality laboratories. Schistosomes are a family of parasitic blood flukes (Phylum Platyhelminthes), which have seven pairs of autosomal chromosomes and one pair of sex chromosomes (ZZ for a male worm and ZW for a female), of a haploid genome size of 2.7x108 base pairs (Simpson et al. 1982). Schistosomes are ideal model organisms for the development of genome mapping strategies since they have a small genome size comparable to that of well-characterized model organisms such as Caenorhabditis elegans (100 Mb) and Drosophila (165 Mb), and contain functional genes with a high level of homology to the host mammalian genes. Here we summarize the current progress in the schistosome genome project, the information of 3,047 transcribed genes (Expressed Sequence Tags; EST), complete sets of cDNA and genomic DNA libraries (including YAC and cosmid libraries) with a mapping technique to the well defined schistosome chromosomes. The schistosome genome project will further identify and characterize the key molecules that are responsible for host-parasite adaptation, i.e., successful growth, development, maturation and reproduction of the parasite within its host in the near future

Evolution, maintenance and ecological consequences of genetic caste determination in " Pogonomyrmex " harvester ants

Summary Division of labor between reproducers (queens) and helpers (workers) is the main characteristic of social insect societies and at the root of their ecological success. Kin selection models predict that phenotypic differences between queens and workers should result from environmental rather than from genetic differences. However, genetic effects on queen and worker differentiation were found in two populations-of Pogonomyrmex harvester ants. Each of the two populations is composed of two genetically distinct lineages. Queens (which can be of either lineage) generally mate with males of their own and of the alternate lineage and produce two types of female offspring, those fertilized by males of the queens' lineage which develop into queens and those fertilized by males of the alternate lineage which develop into workers. All four lineages were further suggested to be themselves of hybrid origin between-the species P: barbatus and P. rugosus, in which queens and workers do not differ genetically. In a first set of experiments, we tested if female caste determination (the differentiation into queens and workers) in the lineages was genetically hardwired and if it was associated with costs in terms of the ability to optimally allocate resources to the production of queens and workers. To this end we first mated queens of-two lineages to a single male. Queens mated to a male of the alternate lineage successfully raised worker offspring whereas queens mated to a male of their own lineage almost always failed to produce workers. This reveals that pure-lineage individuals have lost the ability to develop into workers. Second, we analyzed offspring produced by naturally mated queens. During the stage of colony founding when only workers are produced, naturally mated queens laid a high proportion of pure-lineage eggs but the large majority of these eggs failed to develop. As a consequence, the number of offspring produced by incipient colonies decreased linearly with the proportion of pure-lineage eggs laid by queens. Moreover, queens of the lineage most commonly represented in a given population produced more pure-lineage eggs, in line with the view that they mate randomly with the two types of males and indiscriminately use their sperm. Altogether these results predict frequency-dependent founding success for pairs of lineages because queens of the more common lineage will produce more pure-lineage eggs and their colonies be less successful during the stage of colony founding. To describe the distribution of populations characterized with genetic caste determination relative to the populations with environmental caste determination we genotyped queens and workers collected during a large survey of -additional populations. Genetic caste determination associated with pairs of interbreeding lineages was frequent and widespread in the studied range and we identified four additional lineages displaying genetic caste determination. Overall, there were thus eight highly differentiated lineages with genetic caste determination. These lineages always co-occurred in the same complementary lineage pairs. Three of the four lineage pairs appeared to have a common origin, while their relationship with the forth could not be resolved. The genetic survey also revealed that, in addition to being genetically isolated from one another, all eight lineages were genetically distinct from P. rugosus and P. barbatus, even when colonies of interbreeding lineages co-occurred with colonies of either putative parent at the same site. This raised the question of the mechanisms involved in the reproductive isolation between the lineages and the parental species and between the two lineages of a lineage pair. At a site where one lineage pair co-occurred with P. rugosus, we identified two pre-zygotic mechanisms (differences in timing for mating flights between P. rugosus and the lineage pair and assortative mating) and one post-zygotic mechanism (high levels of hybrid unviablility) which in combination may largely account for the reproductive isolation between the lineages and their parental species. The mechanisms accounting for the reproductive isolation between the two lineages of a lineage pair varied across lineage pairs. In one lineage pair, inter-lineage individuals exclusively occurred in the sterile worker caste, raising the possibility that inter-lineage eggs have completely lost the ability to develop into queens in this lineage pair and that there is thus no opportunity for gene flow. In each of the three remaining lineage pairs, inter-lineage queens were produced by a minority of colonies. In these lineage pairs, colonies headed by inter-lineage queens failed to grow sufficiently to produce reproductive individuals which may account for the reproductive isolation between co-occurring lineages in three lineage pairs. In conclusion, the results of this thesis show that genetic caste determination is costly but widespread in Pogonomyrmex harvester ants. Reproductive isolation among the lineages and between the lineages and the parental species as well as frequency-dependent founding success for co-occurring lineages may contribute to the persistence of this extraordinary system. Résumé La division du travail entre individus reproducteurs (les reines) et individus non-reproducteurs (ouvrières) représente la caractéristique principale des sociétés d'insectes et est à la base de leur succès écologique. Des modèles de sélection de parentèle prédisent que les différences phénotypiques entre reines et ouvrières devraient provenir d'effets environnementaux plutôt que de différences génétiques. Malgré ce fait, des effets génétiques sur la différentiation entre reines et ouvrières ont été montrés dans deux populations de fourmis moissonneuses du genre Pogonomyrmex. Chacune des deux populations est composée de deux lignées génétiquement distinctes. Les reines de chaque lignée s'accouplent en général avec des mâles de leur propre lignée ainsi qu'avec des mâles de l'autre lignée et produisent deux types d'oeufs, ceux qui sont fécondés par les mâles de leur propre lignée qui se développent en nouvelles reines et ceux qui sont fécondés par les mâles de l'autre lignée qui se développent en ouvrières. Il a été suggéré que les lignées sont elles-mêmes des hybrides entre les deux espèces P. barbatus et P. rugosus. Dans ces deux espèces, les reines et ouvrières ne sont pas génétiquement distinctes. Dans une première série d'expériences, nous avons testé si la détermination de la caste femelle (le développement en reine ou en ouvrière) est génétiquement rigide et si elle est associée à des coûts en terme de capacité à allouer de façon optimale les ressources pour la production de reines et d'ouvrières. Pour cela nous avons accouplé des reines de deux lignées avec un seul mâle. Les reines accouplées avec un mâle de l'autre lignée ont élevé de nouvelles ouvrières avec succès alors que les reines accouplées avec un mâle de leur propre lignée ont presque toujours échoué à produire des ouvrières. Ceci montre que les individus de lignée pure ont perdu la capacité de se développer en ouvrière. Deuxièmement, nous avons analysé la descendance de reines qui se sont accouplées naturellement. Durant le stade de fondation de la colonie, où seules des ouvrières sont élevées, les reines accouplées naturellement ont pondu une grande proportion d'oeufs de lignée pure mais la majorité de ces derniers ne se sont pas développés. En conséquence, le nombre de descendants produits par des colonies fondatrices diminuait linéairement avec la proportion des oeufs de lignée pure pondus par la reine en accord avec l'hypothèse que les reines s'accouplent au hasard avec les deux types de mâles et utilisent leur sperme aléatoirement. Dans l'ensemble; ces résultats prédisent un succès de fondation fréquence-dépendant pour les deux lignées, car les reines de la lignée la plus fréquente produiront .plus d'oeufs de lignée pure et leurs colonies auront moins de succès lors de la fondation de colonies par rapport aux colonies de la lignée la moins fréquente. Pour décrire la distribution des-populations caractérisées par une détermination génétique des castes par rapport aux populations caractérisées par une détermination environnementale des castes, nous avons génotypé des reines et des ouvrières qui ont été collectées lors d'une analyse de populations supplémentaires. La détermination génétique des castes associée à des croisements entre lignées est fréquente et largement répartie dans l'aire étudiée. Nous avons identifié quatre lignées supplémentaires, ayant une détermination génétique des castes, pour un total de huit lignées. Ces huit lignées forment quatre paires de lignées et on ne trouve jamais deux lignées de paires différentes, dans une population. Trois des quatre paires de lignées s'avèrent avoir une origine commune alors que leur relation avec la quatrième paire de lignées n'a pas pu être résolue. L'analyse génétique de populations supplémentaires a également révélé qu'en plus d'être génétiquement isolées les unes des autres, les huit lignées sont génétiquement distinctes de P. rugosus et P. barbatus même si les colonies d'une paire de lignées se trouvent en sympatrie avec l'une ou l'autre des espèces parentales. Ceci relève la question des mécanismes impliqués dans l'isolation reproductive entre les lignées et les espèces parentales ainsi qu'entre les deux lignées d'une paire. En étudiant un site où une paire de lignées se trouve en sympatrie avec P. rugosus, nous avons identifié deux mécanismes pré-zygotiques (des différences dans le timing du vol nuptial entre P. rugosus et les lignées et des accouplements assortis) ainsi qu'un mécanisme post-zygotique (un niveau élevé de non-viabilité des hybrides). En combinaison, ces mécanismes peuvent largement expliquer l'isolement reproductif entre les lignées et leurs espèces parentales. Les mécanismes contribuant à l'isolement reproductif entre les deux lignées d'une paire variaient entre paires de lignées. Dans une paire, les individus de génotype inter-lignée se trouvent uniquement dans la caste stérile des ouvrières, suggérant qu'il n'y a pas d'opportunité pour avoir du flux de gènes entre les deux lignées ce cette paire. Dans chacune des trois autres paires de lignées des nouvelles reines de génotype inter-lignée sont produites par une minorité de colonies. Par contre, les colonies avec une reine mère de génotype inter-lignée ne se développent pas suffisamment pour produire des individus reproducteurs. Ceci peut donc expliquer pourquoi il n'y a pas de flux de gènes entre les deux lignées de trois paires. En conclusion, les résultats de cette thèse montrent que la détermination génétique de la caste est coûteuse mais très répandue chez les fourmis. moissonneuses du genre Pogonomyrmex. L'isolement reproductif des lignées entre elles et avec les espèces parentales, ainsi qu'un succès de fondation fréquence-dépendant contribuent à la persistance de ce système extraordinaire.

Giardia agilis: Ultrastructure of the Trophozoites in the Frog Intestine

Intestine samples of Bufo sp. tadpoles with parasitism confirmed for Giardia agilis were studied by transmission electron microscopy. The G. agilis trophozoites were long and thin. The plasma membrane was sometimes undulated and the cytoplasm, adjacent to the dorsal and ventral regions, showed numerous vacuoles. The two nuclei presented prominent nucleoli. The cytoplasm was electron-dense with free ribosomes, glycogen and rough endoplasmic reticulum-like structures. Polyhedral inclusions were observed in the cytoplasm and outside the protozoan; some of these inclusions exhibited membrane disruption. The flagella ultrastructure is typical, with the caudal pair accompanied by the funis. Next to the anterior pair, osmiophilic material was noticed. The ventro-lateral flange was short and thick, supported by the marginal plates that penetrated into its distal extremity; only its distal portion had adjacent osmiophilic filament. The G. agilis trophozoites showed the general subcellular feature of the genus. However, the ventro-lateral flange ultrastructure was an intermediate type between G. muris and G. duodenalis.