Studies on survival, biological activities and behavior of Biomphalaria glabrata, the host snail of Schistosomiasis, submitted to increased hydrostatic pressure: a technique

To study changes in survival, in biological activities and behavior of planorbids submitted to increased hydrostatic pressure, we developed a technique using two transparent chambers and a hydraulic piston. The apparatus permitted renewal of the liquid medium without substantial variations in pressure, thus eliminating excretion products and maintaining the desired O2 level and thereby permitting us to evaluate the effects of pressure independently of the occurrence of anoxia. Pressure was maintained without any contact of the liquid medium with compressed air, a situation which reproduced with relative fidelity what occurs in nature and assured the presence of the same amounts of gases in the two observation chambers (Control and Experimental). Biomphalaria glabrata was found to be able to survive at least 48 hours when submitted to 49.02 x 10**4 Pa (equivalent to a water depth of 48.8 m), continuing to day egg masses and showing few behavioral changes when compared with the control group.

Biological aspects of the DM28C clone of Trypanosoma cruzi after metacylogenesis in chemically defined media

The biological characterization of the Trypanosoma cruzi clone Dm 28c in terms of its growth in LIT medium, cell-cycle, infectivity to mice and interaction with professional and non-professional phagocytic cells shows that it behaves as a bona fide T. cruzi representant. The biological properties of this myotropic clone do not change according to the origin of the trypomastigote forms (i. e., from triatomines, infected mice, cell-culture or from the chemically defined TAUP and TAU3AAG media). In addition Dm 28c metacyclic trypomastigotes from TAU3AAG medium display a high infectivity level to fibroblasts and muscle cells. Experiments on binding of cationized ferritin to trypomastigotes surface show the existence of cap-like structures of ferritin in regions near the kinetoplast. However the nature and role of these anionic sites remain to be determined. The results indicate that metacyclic trypomastigotes from Dm 28c clone obtained under chemically defined conditions reproduce the biological behaviour of T. cruzi, rendering this system very suitable for the study of cell-parasite interactions and for the isolation of trypanosome relevant macromolecules.

Plasmodium falciparum merozoite surface protein 2: epitope mapping and biological activity analysis of specific antibodies

Background: Plasmodium falciparum(P. falciparum) merozoite surfaceprotein 2 (MSP-2) is one of bloodstage proteins that are associated withprotection from malaria. MSP-2 consistsof a highly polymorphic centralrepeat region flanked by a dimorphicregion that defines the two allelicfamilies, 3D7 and FC27; N- and Cterminalregions are conserved domains.Long synthetic peptides (LSP)representing the two allelic familiesof MSP-2 and constant regions arerecognized by sera from donors livingin endemic areas; and specific antibodies(Abs) are associated with protectionand active in antibody dependentcellular inhibition (ADCI) in vitro.However, the fine specificity ofAb response to the two allelic familiesof MSP-2 is unknown. Methods: Peptidesrepresenting dimorphic regionof 3D7 and FC27 families and theirC-terminal (common fragment to thetwo families) termed 3D7-D (88 aa),FC27-D (48 aa) and C (40 aa) respectivelywere synthesized. Overlapping20 mer peptides covering dimorphicand constant regions of two familieswere also synthesized for epitopemapping. Human sera were obtainedfrom donors living in malaria endemicareas. SpecificDand CregionsAbs were purified from single or poolhuman sera. Sera from mice were obtainedafter immunization with thetwo families LSP mixture in three differentadjuvants: alhydrogel (Alum),Glucopyranosyl Lipid Adjuvant-Stableoil-in-water Emulsion (GLA-SE)and Virosome. For ADCI, P. falciparum(strain 3D7) parasite wasmaintained in culture at 0.5% parasitemiaand 4% hematocrit in air tightbox at love oxygen (2%) and 37 ºC.Results: We identified several epitopesfrom the dimorphic and constantregions of both families of MSP-2, inmice and humans (adults and children).In human, most recognizedepitopes were the same in differentendemic regions for each domain ofthe two families of MSP-2. In mice,the differential recognition of epitopewas depending on the strain of mouseand interestingly on the adjuvantused. GLA-SE and alum as adjuvantswere more often associated with therecognition of multiple epitopes thanvirosomes. Epitope-specific Abs recognizednative merozoites of P.falciparum and were active in ADCIto block development of parasite.Conclusion: The delineation of a limitednumber of epitopes could be exploitedto develop MSP-2 vaccinesactive on both allelic families ofMSP-2.

Volumetric MRI changes, cognition and personality traits in old age depression.

BACKGROUND: The presence of cognitive and structural deficits in euthymic elderly depressed patients remains a matter of debate. Integrative aetiological models assessing concomitantly these parameters as well as markers of psychological vulnerability such as persistent personality traits, are still lacking for this age group. METHODS: Cross-sectional comparisons of 38 elderly remitted patients with early-onset depression (EOD) and 62 healthy controls included detailed neuropsychological assessment, estimates of brain volumes in limbic areas and white matter hyperintensities, as well as evaluation of the Five-Factor personality dimensions. RESULTS: Both cognitive performances and brain volumes were preserved in euthymic EOD patients. No significant group differences were observed in white matter hyperintensity scores between the two groups. In contrast, EOD was associated with significant increase of Neuroticism and decrease of Extraversion facet scores. LIMITATIONS: Results concern the restricted portion of EOD patients without psychiatric and physical comorbidities. Future longitudinal studies are necessary to determine the temporal relationship between the occurrence of depression and personality dimensions. CONCLUSIONS: After remission from acute depressive symptoms, cognitive performances remain intact in elderly patients with EOD. In contrast to previous observations, these patients display neither significant brain volume loss in limbic areas nor increased vascular burden compared to healthy controls. Further clinical investigations on EOD patterns of vulnerability in old age will gain from focusing on psychological features such as personality traits rather than neurocognitive clues.

The origins of C4 grasslands: integrating evolutionary and ecosystem science.

The evolution of grasses using C4 photosynthesis and their sudden rise to ecological dominance 3 to 8 million years ago is among the most dramatic examples of biome assembly in the geological record. A growing body of work suggests that the patterns and drivers of C4 grassland expansion were considerably more complex than originally assumed. Previous research has benefited substantially from dialog between geologists and ecologists, but current research must now integrate fully with phylogenetics. A synthesis of grass evolutionary biology with grassland ecosystem science will further our knowledge of the evolution of traits that promote dominance in grassland systems and will provide a new context in which to evaluate the relative importance of C4 photosynthesis in transforming ecosystems across large regions of Earth.

Implicit attitudes and self-concepts towards transgression and aggression: Differences between male community and offender adolescents, and associations with psychopathic traits.

Research suggests that implicit attitudes play a key role in the occurrence of antisocial behaviours. This study assessed implicit attitudes and self-concepts related to aggression and transgression in community and offender adolescents, using a new set of Implicit Association Tests (IATs), and examined their association with of psychopathic traits. Thirty-six offenders and 66 community adolescents performed 4 IATs assessing 1) implicit attitudes about a) aggression and b) transgression as good, and 2) implicit self-concepts about a) aggression and b) transgression as self-descriptive. They filled in self-report questionnaires: the Youth Psychopathic Traits Inventory, the Child Behaviour Checklist, and explicit measures of their attitudes and self-concepts towards transgression and aggression. Results showed few differences between community and offender adolescents on implicit attitudes and self-concepts, and unexpected negative associations between some implicit attitudes and psychopathic traits, while the association was positive for the corresponding explicit attitudes. Possible explanations of these findings are discussed.

Genetics of decayed sexual traits in a parasitoid wasp with endosymbiont-induced asexuality.

Trait decay may occur when selective pressures shift, owing to changes in environment or life style, rendering formerly adaptive traits non-functional or even maladaptive. It remains largely unknown if such decay would stem from multiple mutations with small effects or rather involve few loci with major phenotypic effects. Here, we investigate the decay of female sexual traits, and the genetic causes thereof, in a transition from haplodiploid sexual reproduction to endosymbiont-induced asexual reproduction in the parasitoid wasp Asobara japonica. We take advantage of the fact that asexual females cured of their endosymbionts produce sons instead of daughters, and that these sons can be crossed with sexual females. By combining behavioral experiments with crosses designed to introgress alleles from the asexual into the sexual genome, we found that sexual attractiveness, mating, egg fertilization and plastic adjustment of offspring sex ratio (in response to variation in local mate competition) are decayed in asexual A. japonica females. Furthermore, introgression experiments revealed that the propensity for cured asexual females to produce only sons (because of decayed sexual attractiveness, mating behavior and/or egg fertilization) is likely caused by recessive genetic effects at a single locus. Recessive effects were also found to cause decay of plastic sex-ratio adjustment under variable levels of local mate competition. Our results suggest that few recessive mutations drive decay of female sexual traits, at least in asexual species deriving from haplodiploid sexual ancestors.

Biological control of Biomphalaria tenagophila (Mollusca, Planorbidae), a schistosomiasis vector, using the fish Geophagus brasiliensis (Pisces, Cichlidae) in the laboratory or in a seminatural environment

In order to investigate a possible method of biological control of schistosomiasis, we used the fish Geophagus brasiliensis (Quoy & Gaimard, 1824) which is widely distributed throughout Brazil, to interrupt the life cycle of the snail Biomphalaria tenagophila (Orbigny, 1835), an intermediate host of Schistosoma mansoni. In the laboratory, predation eliminated 97.6% of the smaller snails (3-8 mm shell diameter) and 9.2% of the larger ones (12-14 mm shell diameter). Very promising results were also obtained in a seminatural environment. Studies of this fish in natural snail habitats should be further encouraged.

Combinatorial Synthesis and Biological Evaluation of Inhibitors of D-Ala-D-Ala-Ligase

Report for the scientific sojourn carried out at the Max Planck Institut of Molecular Phisiology, Germany, from 2006 to 2008.The work carried out during this postdoctoral stage was focused on two different projects. Firstly, identification of D-Ala D-Ala Inhibitors and the development of new synthethic approaches to obtain lipidated peptides and proteins and the use of these lipidated proteins in biological and biophysical studies. In the first project, new D-Ala D-Ala inhibitors were identified by using structural alignments of the ATP binding sites of the bacterial ligase DDl and protein and lipid kinases in complex with ATP analogs. We tested a series of commercially available kinase inhibitors and found LFM-A13 and Tyrphostine derivatives to inhibit DDl enzyme activity. Based on the initial screening results we synthesized a series of malononitrilamide and salicylamide derivatives and were able to confirm the validity of these scaffolds as inhibitors of DDl. From this investigation we gained a better understanding of the structural requirements and limitations necessary for the preparation of ATP competitive DDl inhibitors. The compounds in this study may serve as starting points for the development of bi-substrate inhibitors that incorporate both, an ATP competitive and a substrate competitive moiety. Bisubstrate inhibitors that block the ATP and D-Ala binding sites should exhibit enhanced selectivity and potency profiles by preferentially inhibiting DDl over kinases. In the second project, an optimized synthesis for tha alkylation of cysteins using the thiol ene reaction was establisehd. This new protocol allowed us to obtain large amounts of hexadecylated cysteine that was required for the synthesis of differently lipidated peptides. Afterwards the synthesis of various N-ras peptides bearing different lipid anchors was performed and the peptides were ligated to a truncated N-ras protein. The influence of this differently lipidated N-ras proteins on the partioning and association of N-Ras in model membrane subdomains was studied using Atomic Force Microscopy.

Personality traits and behavioural and psychological symptoms in patients with mild cognitive impairment.

BACKGROUND AND AIMS: Both personality changes and behavioural and psychological symptoms (BPS) may be associated with mild cognitive impairment (MCI) in later life and help identify incipient dementia. We wished to investigate the links between personality and BPS in MCI. METHOD: We studied premorbid personality traits as estimated 5 years back and their changes in 83 control subjects and 52 MCI patients using the revised NEO Personality Inventory for the Five-Factor Model completed by a proxy. Information on BPS was obtained using the Neuropsychiatric Inventory (NPI). Analyses were controlled for current depression and anxiety. RESULTS: Premorbid neuroticism and openness to experience were associated with the total NPI score. The changes in neuroticism, extraversion, openness to experiences, and conscientiousness were associated with apathy and affective symptoms. CONCLUSIONS: Personality changes and BPS occur in MCI. The occurrence of affective BPS and apathy is associated with both premorbid personality traits and their changes.

Two Studies on the Interplay between Social Preferences and Individual Biological Features

Biological features and social preferences have been studied separately as factors influencing human strategic behaviour. We run two studies in order to explore the interplay between these two sets of factors. In the first study, we investigate to what extent social preferences may have some biological underpinnings. We use simple one-shot distribution experiments to attribute subjects one out of four types of social preferences: Self-interested (SI), Competitive (C), Inequality averse (IA) and Efficiency-seeking (ES). We then investigate whether these four groups display differences in their levels of facial Fluctuating Asymmetry (FA) and in proxies for exposure to testosterone during phoetal development and puberty. We observe that development-related biological features and social preferences are relatively independent. In the second study, we compare the relative weight of these two set of factors by studying how they affect subjects’ behaviour in the Ultimatum Game (UG). We find differences in offers made and rejection rates across the four social preference groups. The effect of social preferences is stronger than the effect of biological features even though the latter is significant. We also report a novel link between facial masculinity (a proxy for exposure to testosterone during puberty) and rejection rates in the UG. Our results suggest that biological features influence behaviour both directly and through their relation with the type of social preferences that individuals hold.