11-Dehydro-thromboxane B2, a stable thromboxane metabolite, is a full agonist of chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2) in human eosinophils and basophils

Thromboxane (TX) A(2), a cyclooxygenase-derived mediator involved in allergic responses, is rapidly converted in vivo to a stable metabolite, 11-dehydro-TXB(2), which is considered to be biologically inactive. In this study, we found that 11-dehydro-TXB(2), but not the TXA(2) analogue U46,619 or TXB(2), activated eosinophils and basophils, as assayed by flow cytometric shape change. 11-Dehydro-TXB(2) was also chemotactic for eosinophils but did not induce, nor inhibit, platelet aggregation. Chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2) is an important chemoattractant receptor expressed by eosinophils, basophils, and TH2 lymphocytes, and prostaglandin (PG)D(2) has been shown to be its principal ligand. 11-Dehydro-TXB(2) induced calcium flux mainly from intracellular stores in eosinophils, and this response was desensitized after stimulation with PGD(2) but not other eosinophil chemoattractants. Shape change responses of eosinophils and basophils to 11-dehydro-TXB(2) were inhibited by the thromboxane (TP)/CRTH2 receptor antagonist ramatroban, but not the selective TP antagonist SQ29,548, and were insensitive to pertussis toxin. The phospholipase C inhibitor U73,122 attenuated both 11-dehydro-TXB(2)- and PGD(2)-induced shape change. 11-Dehydro-TXB(2) also induced the chemotaxis of BaF/3 cells transfected with hCRTH2 but not naive BaF/3 cells. At a threshold concentration, 11-dehydro-TXB(2) had no antagonistic effect on CRTH2-mediated responses as induced by PGD2. These data show that 11-dehydro-TXB(2) is a full agonist of the CRTH2 receptor and hence might cause CRTH2 activation in cellular contexts where PGD-synthase is not present. Given its production in the allergic lung, antagonism of the 11-dehydro-TXB(2)/CRTH2axis may be of therapeutic relevance.     

Sex chromosomes evolved from independent ancestral linkage groups in winged insects

The evolution of a pair of chromosomes that differ in appearance between males and females (heteromorphic sex chromosomes) has occurred repeatedly across plants and animals. Recent work has shown that the male heterogametic (XY) and female heterogametic (ZW) sex chromosomes evolved independently from different pairs of homomorphic autosomes in the common ancestor of birds and mammals but also that X and Z chromosomes share many convergent molecular features. However, little is known about how often heteromorphic sex chromosomes have either evolved convergently from different autosomes or in parallel from the same pair of autosomes and how universal patterns of molecular evolution on sex chromosomes really are. Among winged insects with sequenced genomes, there are male heterogametic species in both the Diptera (e.g., Drosophila melanogaster) and the Coleoptera (Tribolium castaneum), female heterogametic species in the Lepidoptera (Bombyx mori), and haplodiploid species in the Hymenoptera (e.g., Nasonia vitripennis). By determining orthologous relationships among genes on the X and Z chromosomes of insects with sequenced genomes, we are able to show that these chromosomes are not homologous to one another but are homologous to autosomes in each of the other species. These results strongly imply that heteromorphic sex chromosomes have evolved independently from different pairs of ancestral chromosomes in each of the insect orders studied. We also find that the convergently evolved X chromosomes of Diptera and Coleoptera share genomic features with each other and with vertebrate X chromosomes, including excess gene movement from the X to the autosomes. However, other patterns of molecular evolution--such as increased codon bias, decreased gene density, and the paucity of male-biased genes on the X--differ among the insect X and Z chromosomes. Our results provide evidence for both differences and nearly universal similarities in patterns of evolution among independently derived sex chromosomes.     

A novel artificial habitat collection device for studying resettlement patterns in anguillid glass eels

The number of glass eels Anguilla australis and A. reinhardtii caught in artificial habitat collectors, made from a PVC base and polyethylene split rope fibres, was related to the number of rope fibre tufts attached to each collector rather than collector area directly. Ageing of collectors in situ to promote algal growth enhanced the catch of glass eels. Glass eels entered the collectors at night primarily during the flood tide, and did not move into the collectors during daylight hours. Glass eel abundance increased with increasing distance from the freshwater drain located in the causeway. The artificial habitat collectors are effective for assessing relative numbers of resettling glass eels and may be useful for studying recruitment and settlement patterns of other anguillid eel species, as well as identifying areas and habitats within a catchment that provide important shelter for glass eels. Sampling glass eels can be carried out with maximum effect and minimum effort using compact, aged artificial habitat collectors on the night time flood tide when low tide coincides with dusk.     

Discovery of selective hydroxamic acid inhibitors of tumor necrosis factor-alpha converting enzyme.

Modification of the P(1)' substituent of macrocyclic matrix metalloproteinase (MMP) inhibitors provided compounds that are selective for inhibition of tumor necrosis factor-alpha converting enzyme (TACE) over MMP-1 and MMP-2. Several analogues potently inhibited the release of TNF-alpha in a THP-1 cellular assay. Compounds containing a trimethoxyphenyl group in the P(1)' substituent demonstrated TACE selectivity across several series of hydroxamate-based inhibitors.     

Sexual dimorphism and gonadal development of the Australian longfinned river eel

The sex and stage of gonadal development of longfinned river eels Anguilla reinhardtii , captured from nine river catchments in New South Wales, Australia, between 1999 and 2001, were determined macroscopically. Sex was verified by histology. Histology was also necessary, however, to accurately define stages of gonadal development, particularly in individuals <600 mm in total body length. Anguilla reinhardtii displayed asynchronous gamete development. The most advanced cells present in migrating male and female A. reinhardtii were spermatocytes and pre-vitellogenic oocytes, respectively. Gonadal development stages were positively correlated with body size in both sexes. Females, however, were significantly larger than males and their gonads matured over a broader size range. Size at sexual differentiation (42–60 cm for males and 50–76 cm for females) was much larger than for most other anguillids that have been studied, with the exception of the New Zealand longfinned eel Anguilla dieffenbachii . Corresponding with its large range in size at sexual differentiation was a relatively large range in size at migration for both males (44–62 cm) and females (74–142 cm).     

Feeding ecology and ecomorphology of cichlid assemblages in a large Mesoamerican river delta

Fish assemblages in tropical lowland rivers are characterized by a high richness of species that feed on a diverse array of food resources. Although closely related species often have similar feeding ecology, species within the family Cichlidae display a broad spectrum of trophic niches, and resource partitioning has been inferred from studies conducted in Neotropical rivers. We investigated interspecific variation in food resource use and its relationship to morphological variation among cichlid fishes within the Pantanos de Centla Biosphere Reserve, a coastal area encompassing the delta of the Grijalva-Usumacinta River in Tabasco, Mexico. Most species consumed benthic crustaceans, aquatic insect larvae, and detritus, but some were more herbivorous, and one species was a specialized piscivore. Dietary niche overlap among species was higher than expected for one assemblage, and similar to random expectations for another, suggesting a lesser role for resource partitioning than has been shown for some cichlid assemblages, perhaps due to availability of abundant resources, even in low-water conditions. Canonical correspondence analysis revealed that greatest morphological differences am7ong species involved functional traits directly associated with resource use. Relationships between feeding ecology and morphology were similar to those described for other riverine cichlids. Strong ecomorphological relationships facilitate inferences about the ecology of cichlid species, including species that currently lack data from field studies. Knowledge of ecological relationships will be important for conservation in the Pantanos de Centla, an ecosystem of global significance for biodiversity and ecosystem services.     

Variability in growth of longfinned eels among coastal catchments of south‐eastern Australia

Longfinned eels Anguilla reinhardtii were captured by both fishery‐dependent and independent sampling methods from three rivers in New South Wales, south‐eastern Australia. Growth rates were examined in two zones (fresh water and tidal) in the Hacking, Hawkesbury and Clarence Rivers. Mean annual growth increments of sampled longfinned eels ranged from 30 to 60 mm year⁻¹ using age‐length analyses and up to 167 mm year⁻¹ based on tag‐recapture model estimates (GROTAG), with both methods showing high intra‐ and inter‐population variability. Growth was significantly faster in younger (5–15 years) fish than older (>15 years) fish, with females growing an average 10 mm year⁻¹ faster than males of similar age and capture location. Longfinned eels found in tidal areas grew significantly faster than those in non‐tidal freshwater areas as a result of longer growing seasons in the highly productive estuarine habitats. Other possible factors influencing variability in growth rates for this species include habitat preference, density and fishing pressure.