Taste and Physiological Responses to Glucosinolates: Seed Predator versus Seed Disperser

In contrast to most other plant tissues, fleshy fruits are meant to be eaten in order to facilitate seed dispersal. Although fleshy fruits attract consumers, they may also contain toxic secondary metabolites. However, studies that link the effect of fruit toxins with seed dispersal and predation are scarce. Glucosinolates (GLSs) are a family of bitter-tasting compounds. The fleshy fruit pulp of Ochradenus baccatus was previously found to harbor high concentrations of GLSs, whereas the myrosinase enzyme, which breaks down GLSs to produce foul tasting chemicals, was found only in the seeds. Here we show the differential behavioral and physiological responses of three rodent species to high dose (80%) Ochradenus’ fruits diets. Acomys russatus, a predator of Ochradenus’ seeds, was the least sensitive to the taste of the fruit and the only rodent to exhibit taste-related physiological adaptations to deal with the fruits’ toxins. In contrast, Acomys cahirinus, an Ochradenus seed disperser, was more sensitive to a diet containing the hydrolyzed products of the GLSs. A third rodent (Mus musculus) was deterred from Ochradenus fruits consumption by the GLSs and their hydrolyzed products. We were able to alter M. musculus avoidance of whole fruit consumption by soaking Ochradenus fruits in a water solution containing 1% adenosine monophosphate, which blocks the bitter taste receptor in mice. The observed differential responses of these three rodent species may be due to evolutionary pressures that have enhanced or reduced their sensitivity to the taste of GLSs.     

Tuberculosis Treatment in HIV Infected Ugandans with CD4 Counts >350 Cells/mm3 Reduces Immune Activation with No Effect on HIV Load or CD4 Count

Background

Both HIV and TB cause a state of heightened immune activation. Immune activation in HIV is associated with progression to AIDS. Prior studies, focusing on persons with advanced HIV, have shown no decline in markers of cellular activation in response to TB therapy alone.

Methodology

This prospective cohort study, composed of participants within a larger phase 3 open-label randomized controlled clinical trial, measured the impact of TB treatment on immune activation in persons with non-advanced HIV infection (CD4>350 cells/mm³) and pulmonary TB. HIV load, CD4 count, and markers of immune activation (CD38 and HLA-DR on CD4 and CD8 T cells) were measured prior to starting, during, and for 6 months after completion of standard 6 month anti-tuberculosis (TB) therapy in 38 HIV infected Ugandans with smear and culture confirmed pulmonary TB.

Results

Expression of CD38, and co-expression of CD38 and HLA-DR, on CD8 cells declined significantly within 3 months of starting standard TB therapy in the absence of anti-retroviral therapy, and remained suppressed for 6 months after completion of therapy. In contrast, HIV load and CD4 count remained unchanged throughout the study period.

Conclusion

TB therapy leads to measurable decreases in immune activation in persons with HIV/TB co-infection and CD4 counts >350 cells/mm³.     

Application of DNA amplification fingerprinting (DAF) to mixed culture bioreactors

Summary The use of DNA amplification fingerprinting (DAF) as a tool for monitoring mixed microbial populations in bioreactors was evaluated. Short (8-mer or 10-mer) oligonucleotides were used to prime DNA extracts from various biological reactors during polymerase chain reaction (PCR) amplification. The reactors examined in this study included two sets of anaerobic stirred tank continuous flow bioreactors. One set of anaerobic reactors was operated under methanogenic conditions and one set was operated under sulfate-reducing conditions. The anaerobic reactor communities in the methanol-fed reactors showed extensive DAF homology. DAF was also applied to a fixed-film azo dye degrading reactor to examine the degree of uniformity of colonization of the substratum in representative regions of the reactor. This method is a quick and relatively inexpensive means of monitoring microbial community structure during biological processes. Since no cultivation of the sample is involved, the genetic profile of the community is not biased by outgrowth conditions. DAF profiles may be useful for comparisons of population changes over time or of bench-scale vs pilot-scale reactors but not adequate for assessing community diversity.     

Potent inhibitors of malarial P. Falciparum protein kinase G: Improving the cell activity of a series of imidazopyridines

Development of a class of bicyclic inhibitors of the Plasmodium falciparum cyclic GMP-dependent protein kinase (PfPKG), starting from known compounds with activity against a related parasite PKG orthologue, is reported. Examination of key sub-structural elements led to new compounds with good levels of inhibitory activity against the recombinant kinase and in vitro activity against the parasite. Key examples were shown to possess encouraging in vitro ADME properties, and computational analysis provided valuable insight into the origins of the observed activity profiles.     

A Replicative Plasmid Vector Allows Efficient Complementation of Pathogenic Leptospira Strains

Leptospirosis, an emerging zoonotic disease, remains poorly understood because of a lack of genetic manipulation tools available for pathogenic leptospires. Current genetic manipulation techniques include insertion of DNA by random transposon mutagenesis and homologous recombination via suicide vectors. This study describes the construction of a shuttle vector, pMaORI, that replicates within saprophytic, intermediate, and pathogenic leptospires. The shuttle vector was constructed by the insertion of a 2.9-kb DNA segment including the parA, parB, and rep genes into pMAT, a plasmid that cannot replicate in Leptospira spp. and contains a backbone consisting of an aadA cassette, ori R6K, and oriT RK2/RP4. The inserted DNA segment was isolated from a 52-kb region within Leptospira mayottensis strain 200901116 that is not found in the closely related strain L. mayottensis 200901122. Because of the size of this region and the presence of bacteriophage-like proteins, it is possible that this region is a result of a phage-related genomic island. The stability of the pMaORI plasmid within pathogenic strains was tested by passaging cultures 10 times without selection and confirming the presence of pMaORI. Concordantly, we report the use of trans complementation in the pathogen Leptospira interrogans. Transformation of a pMaORI vector carrying a functional copy of the perR gene in a null mutant background restores the expression of PerR and susceptibility to hydrogen peroxide comparable to that of wild-type cells. In conclusion, we demonstrate the replication of a stable plasmid vector in a large panel of Leptospira strains, including pathogens. The shuttle vector described will expand our ability to perform genetic manipulation of Leptospira spp.     

Adaptive significance of facultative paedomorphosis in Triturus alpestris (Amphibia, Caudata): resource partitioning in an alpine lake

1. Facultative paedomorphosis is a polymorphism that has important evolutionary implications in promoting morphological differentiation and variation in habitat use. It occurs in several urodele species throughout the world. Several hypotheses based on life-history theory have been proposed to explain the wide range of habitats in which facultative paedomorphosis occurs, suggesting multifactorial causes.
2. In harsh habitats, such as mountain lakes, paedomorphosis might promote niche partitioning between morphs. This hypothesis was tested by comparing micro-habitat use and diet of two coexisting morphs in an alpine lake.
3. Paedomorphs occupied all microhabitats in the lake while metamorphs occurred only along the shoreline or at the water surface. Paedomorphic newts were frequent in deep water, where they foraged mainly on plankton. Plankton was poorly exploited by metamorphic newts, which fed mainly on terrestrial insects. Difference between morphs in microhabitat use, and consequently in the diet, were consistent in both sexes and in juveniles.
4. In adults, the mass and energy value of stomach contents did not differ between morphs, suggesting a similar food availability in the habitats occupied.
5. This study indicates habitat partitioning between morphs involving dietary differences. Specific benefits and costs of each ontogenetic pathway may allow their coexistence in this deep and fishless lake. Paedomorphosis benefits individual newts by making new food resources available and presumably reducing competition at the shore of the lake. However, the proximate causes of such an ontogenetic switch remain unclear.     

Evidence for distinct polygenic regulation of antibody responses to some unrelated antigens in lines of mice selected for high or low antibody responses to somatic antigen of Salmonella

The effect of the selective breeding of mice for high or low antibody production to complex immunogens is largely nonspecific, since it modifies the responsiveness of high (H) and low (L) lines to many antigens unrelated to the selection antigen. However, the nonspecific effect of the polygenic control operating in these lines is not a general feature. For example, the group of genes in selection IV, carried out for responsiveness to somatic antigen of Salmonella, does not modify the responses to sheep erythrocytes (SE). Despite equivalent responses in H and L mice of selection IV, a large variability was found in individual responses of F₂ interline hybrids, which demonstrates the presence of alleles with high or low effect on responses to SE. A selective breeding (Selection IV-A) was therefore initiated from this F₂ population for responsiveness to SE. A progressive interline divergence occurred during the first seven generations of selection; the interline separation was due to polygenic regulation (about four independent loci from a preliminary estimate).Equivalent responses to the s antigen of Salmonella are observed in the two lines. This constitutes additional evidence for distinct polygenic regulation of responses to SE and to somatic antigen. Moreover, the pattern of responses to several unrelated antigens (nonspecific effect) also differs between Selections IV and IV-A.Abbreviations H high responder lines - L low responder lines - s somatic antigen of Salmonella - f flagellar antigen of Salmonella - R response to selection - S selection differential - F₀ foundation population - h² heritability (realized) - RGG rabbit gamma globulin - CE chicken erythrocyte - HE human erythrocyte - PE pigeon erythrocyte - SE sheep erythrocyte