Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

A Novel Flow Cytometric Hemozoin Detection Assay for Real-Time Sensitivity Testing of Plasmodium falciparum

Resistance of Plasmodium falciparum to almost all antimalarial drugs, including the first-line treatment with artemisinins, has been described, representing an obvious threat to malaria control. In vitro antimalarial sensitivity testing is crucial to detect and monitor drug resistance. Current assays have been successfully used to detect drug effects on parasites. However, they have some limitations, such as the use of radioactive or expensive reagents or long incubation times. Here we describe a novel assay to detect antimalarial drug effects, based on flow cytometric detection of hemozoin (Hz), which is rapid and does not require any additional reagents. Hz is an optimal parasite maturation indicator since its amount increases as the parasite matures. Due to its physical property of birefringence, Hz depolarizes light, hence it can be detected using optical methods such as flow cytometry. A common flow cytometer was adapted to detect light depolarization caused by Hz. Synchronized in vitro cultures of P. falciparum were incubated for 48 hours with several antimalarial drugs. Analysis of depolarizing events, corresponding to parasitized red blood cells containing Hz, allowed the detection of parasite maturation. Moreover, chloroquine resistance and the inhibitory effect of all antimalarial drugs tested, except for pyrimethamine, could be determined as early as 18 to 24 hours of incubation. At 24 hours incubation, 50% inhibitory concentrations (IC50) were comparable to previously reported values. These results indicate that the reagent-free, real-time Hz detection assay could become a novel assay for the detection of drug effects on Plasmodium falciparum.     

A Spatially Explicit Model of Synchronization in Fiddler Crab Waving Displays

Fiddler crabs (Uca spp., Decapoda: Ocypodidae) are commonly found forming large aggregations in intertidal zones, where they perform rhythmic waving displays with their greatly enlarged claws. While performing these displays, fiddler crabs often synchronize their behavior with neighboring males, forming the only known synchronized visual courtship displays involving reflected light and moving body parts. Despite being one of the most conspicuous aspects of fiddler crab behavior, little is known about the mechanisms underlying synchronization of male displays. In this study we develop a spatially explicit model of fiddler crab waving displays using coupled logistic map equations. We explored two alternative models in which males either direct their attention at random angles or preferentially toward neighbors. Our results indicate that synchronization is possible over a fairly large region of parameter space. Moreover, our model was capable of generating local synchronization neighborhoods, as commonly observed in fiddler crabs under natural conditions.     

Semen cryopreservation in golden‐headed lion tamarin,Leontopithecus chrysomelas

Wild animal genetic resource banking (GRB) represents a valuable tool in conservation breeding programs, particularly in cases involving endangered species such as the golden‐headed lion tamarin (Leontopithecus chrysomelas). Thus, we aimed to assess a sperm freezing protocol for golden‐headed lion tamarins using two different exenders: BotuBOV® (BB) and Test Yolk Buffer® (TYB). Ejaculates were collected by penile vibrostimulation from animals housed at São Paulo Zoological Park Foundation, São Paulo, Brazil, and after immediate analysis, two aliquots were diluted in BB and TYB. Postthawing samples were evaluated for total and progressive motility, plasma membrane and acrosome integrities, mitochondrial activity, susceptibility to oxidative stress, and sperm–egg‐binding. No differences between BB and TYB were found for most seminal parameters, except for acrosome integrity and susceptibility to oxidative stress (in both cases BB showed higher values). However, in spite of these differences and regardless of the extender used, postthaw sperm motility and viability with the described protocol were encouraging (on average >50% and >80%, respectively), indicating that sperm cryopreservation may be a short‐term measure for the conservation of golden‐headed lion tamarins.     

Paracoccidioides brasiliensis Interferes on Dendritic Cells Maturation by Inhibiting PGE2 Production

Paracoccidioidomycosis (PCM) is a systemic mycosis, endemic in most Latin American countries, especially in Brazil, whose etiologic agent is the thermodimorphic fungus of the genus Paracoccidioides, comprising cryptic species of Paracoccidioides brasiliensis, S1, PS2, PS3 and Paracoccidioides lutzii. The mechanisms involved in the initial interaction of the fungus with cells of the innate immune response, as dendritic cells (DCs), deserve to be studied. Prostaglandins (PGs) are eicosanoids that play an important role in modulating functions of immune cells including DCs. Here we found that human immature DCs derived from the differentiation of monocytes cultured with GM-CSF and IL-4 release substantial concentrations of PGE₂, which, however, were significantly inhibited after challenge with P. brasiliensis. In vitro blocking of pattern recognition receptors (PRRs) by monoclonal antibodies showed the involvement of mannose receptor (MR) in PGE₂ inhibition by the fungus. In addition, phenotyping assays showed that after challenge with the fungus, DCs do not change their phenotype of immature cells to mature ones, as well as do not produce IL-12 p70 or adequate concentrations of TNF-α. Assays using exogenous PGE₂ confirmed an association between PGE₂ inhibition and failure of cells to phenotypically mature in response to P. brasiliensis. We conclude that a P. brasiliensis evasion mechanism exists associated to a dysregulation on DC maturation. These findings may provide novel information for the understanding of the complex interplay between the host and this fungus.     

A para-nitrophenol phosphonate probe labels distinct serine hydrolases of Arabidopsis

Activity-based protein profiling represents a powerful methodology to probe the activity state of enzymes under various physiological conditions. Here we present the development of a para-nitrophenol phosphonate activity-based probe with structural similarities to the potent agrochemical paraoxon. We demonstrate that this probes labels distinct serine hydrolases with the carboxylesterase CXE12 as the predominant target in Arabidopsis thaliana. The designed probe features a distinct labeling pattern and therefore represents a promising chemical tool to investigate physiological roles of selected serine hydrolases such as CXE12 in plant biology.     

Male-Driven Differences in Chimpanzee (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) Population Genetic Structure Across Three Habitats in Cameroon and Nigeria

Complex ecological pressures affect the social dynamics of many primate species, but it is unclear how they affect primate speciation. Molecular tools are often used to answer questions about the evolutionary histories and social systems of primates. Mitochondrial DNA (mtDNA), in particular, is frequently used to answer many of these questions, but because it is passed from mothers to offspring it reveals only the histories of females. In many species, including chimpanzees, females generally disperse from their natal groups while males are philopatric, and thus differences in dispersal patterns likely leave different signatures in the genome. We previously analyzed samples from 187 unrelated male and female chimpanzees in Nigeria and Cameroon using 21 autosomal microsatellites and mtDNA sequences. Here, we examine the contributions of males and females in shaping the genetic history of these chimpanzees by genotyping a subset of 56 males at 12 Y-chromosome microsatellites. We found that Y-chromosome population structure differed from the results of analysis of mtDNA haplotypes. The results also revealed that males in rainforest habitats (Guinean and Congolian rainforests) are more closely related to one another than those inhabiting the savanna-woodland mosaic ecotone in central Cameroon. In contrast, the pattern of female relatedness did not differ across habitats. We hypothesize that these differences in population structure and patterns of relatedness among males in different habitat types may be due to differences in the community dynamics of chimpanzees in the ecotone vs. rainforests, and that these factors contribute to making Cameroon an engine of diversification for chimpanzees. Broadly, these results demonstrate the importance of habitat variation in shaping social systems, population genetics, and primate speciation.