In vitro Culture and Temporary Immersion Bioreactor Production of Crescentia cujete

Crescentia cujete L. is a widely distributed medicinal tree with a diverse range of phytochemicals used as medicinal compounds. Seedlings of wild-harvested C. cujete were established in vitro and used as the starting material for the establishment of axenic cultures. Shoots were proliferated from nodal segments and were maintained over a period of more than 2 years by sequential subculture on a medium containing 1.0 μmol l⁻¹ kinetin. De novo regeneration was induced on petiole sections cultured onto a medium containing thidiazuron in combination with 2,4-dichlorophenoxyacetic acid. Axenic cultures were also used to test the efficiency of three different cultivation systems for production of biomass of C. cujete. Growth of plantlets in a temporary immersion bioreactor resulted in significant increases in biomass, leaf number, shoot height and transplant efficiency. Plantlets grown in the bioreactors were acclimatized under greenhouse conditions. Together, these experiments have established optimized parameters for propagation and growth of C. cujete plantlets in a sterile controlled environment for biochemical characterization and production of high-quality medicinal products.     

SEXUAL SELECTION AND SURVIVAL SELECTION ON WING COLORATION AND BODY SIZE IN THE RUBYSPOT DAMSELFLY HETAERINA AMERICANA

I review methodological problems that can lead to false evidence for selection on secondary sexual characters and present a study of selection in rubyspot damselflies (Hetaerina americana) that avoids these pitfalls. Male rubyspots have a large red spot on each wing that grows to a terminal size after sexual maturity. Selection gradient analyses revealed evidence for positive sexual and survival selection on both terminal wing spot size and body size. Phenotype manipulations confirmed that wing spot size was subject to direct sexual selection, but showed that the positive slope of survival on wing spot size was an indirect effect of selection on unmeasured traits. This study provides the strongest evidence yet for sexual selection on coloration in Odonata, but also provides clear examples of why phenotypic selection statistics must be calculated and interpreted cautiously.     

Carotenoid scarcity, synthetic pteridine pigments and the evolution of sexual coloration in guppies (Poecilia reticulata).

Carotenoid-based sexual coloration is the classic example of an honest signal of mate quality. Animals cannot synthesize carotenoid pigments and ultimately depend on dietary sources. Thus, in carotenoid-poor environments, carotenoid coloration may be a direct indicator of foraging ability and an indirect indicator of health and vigour. Carotenoid coloration may also be affected, more directly, by parasites in some species. Carotenoids are not, however, the only conspicuous pigments available to animals. Pteridine pigments, with similar spectral properties, are displayed in the exoskeletons and wings of insects, the irides of birds and the skins of fishes, lizards and amphibians. Unlike carotenoids, pteridines are synthesized de novo by animals. We report that the orange spots that male guppies (Poecilia reticulata) display to females contain red pteridine pigments (drosopterins) in addition to carotenoids. We also examined the relationship between drosopterin production by males and carotenoid availability in the field. The results contrasted sharply with the hypothesis that males use drosopterins to compensate for carotenoid scarcity: males used more, not less, drosopterins in streams with higher carotenoid availability. The positive association between drosopterin use and carotenoid availability could reflect the costs of drosopterin synthesis or it could be a consequence of females preferring a particular pigment ratio or hue. Male guppies appear to use drosopterin pigments in a manner that dilutes, but does not eliminate, the indicator value of carotenoid coloration.     

Intraepithelial lymphocyte immunophenotype: a useful tool in the diagnosis of celiac disease

According to new ESPGHAN guidelines, gluten challenge is considered necessary when there is doubt about the initial diagnosis of celiac disease (CD). The main aim of this study was to quantify intraepithelial lymphocyte (IEL) immunophenotype on celiac patients on gluten-containing diet (GCD) compared to those on gluten-free diet (GFD). Another aim was to evaluate the clinical utility of IELs in the CD diagnosis, especially in selected patients on GFD where diagnostic uncertainty remains. IEL immunophenotype (TCRγδ and NK-like IELs) were studied by flow cytometry in 111 children with CD (81 children with CD on GCD and 30 celiac patients on GFD) and a control group (10 children). Duration of GFD was 5.4 ± 1.6 years. TCRγδ IELs in celiac patients receiving a GCD or GFD were significantly higher (p < 0.001) than in the control group. NK-like IELs in patients receiving a GCD or GFD were significantly lower than in the control group (p < 0.001). We observed a permanent decrease of NK-like IELs and an increment of TCRγδ IELs after following an adequate establishment and compliance of a long-term GFD in celiac patients. Recognition of IELs changes in the intestinal mucosa on celiac patients after long-term establishment of a GFD could constitute a useful tool for CD diagnosis in various situations: in which there is doubt about the initial diagnosis and repeat biopsy is necessary (avoiding the need of gluten challenges), and in those patients with symptoms/signs suggestive of CD who maintain a low gluten diet.     

Experimental test of the mechanism underlying sexual segregation at communal roosts of harvestmen (Prionostemma spp.)

Closely related, ecologically similar species often roost in distinctly different habitats, and roosting patterns also vary within species in relation to sex, age and season. The causes of such variation are not well understood at either a proximate or ultimate level. We studied communal roosting in two congeneric species of Prionostemma harvestmen at a rainforest site in Nicaragua. Previous research showed that Prionostemma sp. 1 forms male‐biased communal roosts in tree‐root cavities, while Prionostemma sp. 2 forms communal roosts of variable but temporally stable sex ratios on spiny palms. Here, we investigate potential mechanisms underlying variation in roosting site choice between and within these syntopic species. First, we present the results of a field experiment designed to probe the mechanism underlying skewed roost sex ratios in Prionostemma sp. 2. Previous studies have suggested that these harvestmen use conspecific scent to locate communal roosts and that new roosts can be established via group translocation. Therefore, to test the hypothesis that skewed roost sex ratios in this species arise from sex differences in scent marks, we translocated single‐sex groups of ca. 30 individuals to each of 20 previously unoccupied spiny palms. Female release sites attracted new recruits of both sexes, while male release sites attracted almost exclusively males. We infer that Prionostemma sp. 2 females preferentially roost in sites scent‐marked by females and that this mechanism is sufficient to explain the skewed roost ratios. Further adding to knowledge of Prionostemma roosting behavior, we show that Prionostemma sp. 1 forms female‐biased communal roosts on spiny palms, that some roosts contain both species, and that the species composition is stable on a time scale of at least 2 weeks. To the best of our knowledge, this study is the first experimental test of mechanisms underlying sexual segregation at communal roosts in any taxon.     

Predicting the direction of ornament evolution in Trinidadian guppies (Poecilia reticulata)

Sexual selection is thought to be opposed by natural selection such that ornamental traits express a balance between these two antagonistic influences. Phenotypic variation among populations may indicate local shifts in this balance, or that different stable ‘solutions’ are possible, but testing these alternatives presents a major challenge. In the guppy (Poecilia reticulata), a small freshwater fish with male-limited ornamental coloration, these issues can be addressed by transplanting fish among sites of varying predation pressure, thus effectively manipulating the strength and nature of natural selection. Here, we contrast the evolutionary outcome of two such introductions conducted in the Trinidadian El Cedro and Aripo Rivers. We use sophisticated colour appraisal methods that account for full spectrum colour variation and which incorporate the very latest visual sensitivity data for guppies and their predators. Our data indicate that ornamentation evolved along different trajectories: whereas Aripo males evolved more numerous and/or larger orange, black and iridescent markings, El Cedro males only evolved more extensive and brighter iridescence. Examination of the El Cedro experiment also revealed little or no ornamental evolution at the control site over 29 years, which contrasts markedly with the rapid (approx. 2–3 years) changes reported for introduction populations. Finally, whole colour-pattern analysis suggested that the greatest visual difference between El Cedro introduction and control fish would be perceived by the two most salient viewers: guppies and the putatively dangerous predator Crenicichla alta. We discuss whether and how these evolutionary trajectories may result from founder effects, population-specific mate preferences and/or sensory drive.     

The role of interspecific interference competition in character displacement and the evolution of competitor recognition

The extent to which interspecific interference competition has contributed to character evolution is one of the most neglected problems in evolutionary biology. When formerly allopatric species come into secondary contact, aggressive interactions between the species can cause selection on traits that affect interspecific encounter rates (e.g. habitat preferences, activity schedules), competitor recognition (e.g. colouration, song), and fighting ability (e.g. weaponry, body size). We define agonistic character displacement (ACD) as the process of phenotypic evolution in a population caused by interference competition with one or more sympatric species and which results in shifts in traits that affect the rate, intensity or outcome of interspecific aggression. After clarifying the relationships between ACD and other evolutionary processes that may occur when species come into secondary contact, we develop an individual‐based, quantitative genetic model to examine how traits involved in competitor recognition would be expected to evolve under different secondary contact scenarios. Our simulation results show that both divergence and convergence are possible outcomes, depending on the intensity of interspecific exploitative competition, the costs associated with mutual versus unilateral recognition, and the extent of phenotypic differences prior to secondary contact. We then devise a set of eight criteria for evaluating putative examples of ACD and review the empirical literature to assess the strength of existing evidence and to identify promising avenues for future research. Our literature search revealed 33 putative examples of ACD across insects, fishes, bats, birds, lizards, and amphibians (15 divergence examples; 18 convergence examples). Only one example satisfies all eight criteria for demonstrating ACD, but most case studies satisfy four or more criteria. The current state of the evidence for ACD is similar to the state of the evidence for ecological character displacement just 10 years ago. We conclude by offering suggestions for further theoretical and empirical research on ACD.     

Profilin tyrosine phosphorylation in poly-L-proline-binding regions inhibits binding to phosphoinositide 3-kinase in Phaseolus vulgaris

The profilin family consists of a group of ubiquitous highly conserved 12-15 kDa eukaryotic proteins that bind actin, phosphoinositides, poly-l-proline (PLP) and proteins with proline-rich motifs. Some proteins with proline-rich motifs form complexes that have been implicated in the dynamics of the actin cytoskeleton and processes such as vesicular trafficking. A major unanswered question in the field is how profilin achieves the required specificity to bind such an array of proteins. It is now becoming clear that profilin isoforms are subject to differential regulation and that they may play distinct roles within the cell. Considerable evidence suggests that these isoforms have different functional roles in the sorting of diverse proteins with proline-rich motifs. All profilins contain highly conserved aromatic residues involved in PLP binding which are presumably implicated in the interaction with proline-rich motif proteins. We have previously shown that profilin is phosphorylated on tyrosine residues. Here, we show that profilin can bind directly to Phaseolus vulgaris phosphoinositide 3-kinase (PI3K) type III. We demonstrate that a new region around Y72 of profilin, as well as the N- and C-terminal PLP-binding domain, recognizes and binds PLP and PI3K. In vitro binding assays indicate that PI3K type III forms a complex with profilin in a manner that depends on the tyrosine phosphorylation status within the proline-rich-binding domain in profilin. Profilin-PI3K type III interaction suggests that profilin may be involved in membrane trafficking and in linking the endocytic pathway with actin reorganization dynamics.     

Structure-based design of indole propionic acids as novel PPARalpha/gamma co-agonists

In the quest for novel PPARalpha/gamma co-agonists as putative drugs for the treatment of type 2 diabetes and dyslipidemia, we have used a structure-based design approach to identify propionic acids with a 1,5-disubstituted indole scaffold as potent PPARalpha/gamma activators. Compounds 13, 24, and 28 are examples of submicromolar dual agonists with different alpha/gamma EC50 ratios that are selective against the delta-isoform. Analysis of the X-ray complex structure of PPARgamma with the indole propionic acid 13 provides a rationalization for some of the observed SAR.