Adenylate cyclase from sea urchin eggs is positively and negatively regulated by D-1 and D-2 dopamine receptors

The adenylate cyclase present in membranes prepared from sea urchin eggs is sensitive to dopamine stimulation. The receptor sites coupled to sea urchin adenylate cyclase were characterized by means of specific agonists and antagonists. The D-1 dopamine agonist SKF-38393 was able to stimulate enzyme activity, while the two D-1 dopamine antagonists, SCH-23390 and SKF-83566, suppressed the stimulatory effect of dopamine. In addition, the D-2 dopamine agonists, PPHT and metergoline, brought about a dose-dependent inhibition of dopamine-stimulated adenylate cyclase activity. These data show that: (i) in sea urchin eggs adenylate cyclase is regulated by dopamine receptors; (ii) these receptors share characteristics with D-1 and D-2 dopamine receptors present in the mammalian brain.     

In vitro stimulation of C3H/HeJ spleen cells and macrophages by a lipid A precursor molecule derived from Salmonella typhimurium

C3H/HeJ mice possess a genetic lesion that renders them significantly less responsive to the biologic effects of protein-free lipopolysaccharide (LPS) preparations, and more specifically, to the lipid A region of the LPS molecule. The in vivo manifestations of this mutation are also reflected in vitro in that cells derived from this mouse strain fail to respond to LPS when compared with cells derived from fully endotoxin-responsive mouse strains. The precise nature of this gene defect has not yet been established. In this study, we have examined in vitro the biologic activities of a structurally less complex "lipid A precursor" molecule, produced by a conditionally lethal, temperature-sensitive mutant of Salmonella typhimurium. In contrast to the intact LPS or wild-type lipid A extracted from the parental strain of Salmonella typhimurium, the lipid A precursor induced a highly significant, polymyxin B-inhibitable mitogenic response in splenic cultures derived from LPS-hyporesponsive C3H/HeJ and C57BL/10ScN (nu/nu) mice. In addition, the lipid A precursor was found to stimulate cultures of C3H/HeJ macrophages to produce significant levels of both interleukin 1 (IL 1, previously referred to as "lymphocyte activating factor" or "LAF") and prostaglandins of the E series (PGE). These findings suggest the possibility that the defect in endotoxin responsiveness exhibited by C3H/HeJ mice may be related to a defect in the processing of wild-type lipid A or LPS to a suitably stimulatory form that is structurally related to the lipid A precursor molecule.     

Cytoprotection by the NO-Donor SNAP Against Ischemia/Reoxygenation Injury in Mouse Embryonic Stem Cell-Derived Cardiomyocytes

Embryonic stem cell (ESC)-derived cardiomyocytes are a promising cell source for the screening for potential cytoprotective molecules against ischemia/reperfusion injury, however, little is known on their behavior in hypoxia/reoxygenation conditions. Here we tested the cytoprotective effect of the NO-donor SNAP and its downstream cellular pathway. Mouse ESC-derived cardiomyocytes were subjected to 150-min simulated ischemia (SI) followed by 120-min reoxygenation or corresponding non-ischemic conditions. The following treatments were applied during SI or normoxia: the NO-donor S-Nitroso-N-acetyl-d,l-penicillamine (SNAP), the protein kinase G (PKG) inhibitor, the K_ATP channel blocker glibenclamide, the particulate guanylate cyclase activator brain type natriuretic peptide (BNP), and a non-specific NO synthase inhibitor (N-Nitro-l-arginine, l-NNA) alone or in different combinations. Viability of cells was assayed by propidium iodide staining. SNAP attenuated SI-induced cell death in a concentration-dependent manner, and this protection was attenuated by inhibition of either PKG or K_ATP channels. However, SI-induced cell death was not affected by BNP or by l-NNA. We conclude that SNAP protects mESC-derived cardiomyocytes against SI/R injury and that soluble guanylate-cyclase, PKG, and K_ATP channels play a role in the downstream pathway of SNAP-induced cytoprotection. The present mESC-derived cardiomyocyte-based screening platform is a useful tool for discovery of cytoprotective molecules.     

Mechanisms driving the specificity of a myrmecophyte–ant association

In the understory of pristine Guianese forests, the myrmecophyte Hirtella physophora almost exclusively shelters colonies of the plant-ant Allomerus decemarticulatus in its leaf pouches. We experimentally tested three non-mutually exclusive hypotheses concerning phenomena that can determine the species specificity of this association throughout the foundation stage of the colonies: (1) interspecific competition results in the overwhelming presence of A. decemarticulatus queens or incipient colonies; (2) exclusion filters prevent other ant species from entering the leaf pouches; and (3) host-recognition influences the choice of founding queens, especially A. decemarticulatus . Neither interspecific competition, nor the purported exclusion filters that we examined play a major role in maintaining the specificity of this association. Unexpectedly, the plant trichomes lining the domatia appear to serve as construction material during claustral foundation rather than as a filter. Finally, A. decemarticulatus queens are able to identify their host plant from a distance through chemical and/or visual cues, which is rarely demonstrated in studies on obligatory ant–plant associations. We discuss the possibility that this specific host-recognition ability could participate in shaping a compartmentalized plant-ant community where direct competition between ant symbionts is limited.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 90–97.     

The Iberian Peninsula: ancient history of a hot spot of mite harvestmen (Arachnida: Opiliones: Cyphophthalmi: Sironidae) diversity

The Iberian Peninsula represents a hot spot of cyphophthalmid (mite harvestman) disparity, with four of the eight genera currently recognized in the family Sironidae represented in the region – a generic diversity and morphological disparity not found in any other region of the World so far. From these, two genera (Iberosiro and Odontosiro) are monotypic, and are restricted to the western side of the peninsula. Parasiro is restricted to the north‐east region, from the Catalonian Coastal Ranges and both sides of the Eastern Pyrenees, in areas where the annual rainfall surpasses 1000 mm, and mostly restricted to areas with Paleozoic and Variscan rocks, with other species of the genus extending to Corsica, Sardinia, and the Italian Peninsula. A second species of the genus Paramiopsalis, Paramiopsalis eduardoi sp. nov. from Fragas do Eume, is described here along with a re‐diagnosis of the genus. Paramiopsalis species, together with Odontosiro, inhabit the north‐west corner of the Iberian Peninsula, an area with some of the highest recorded annual rainfall, and with Paleozoic rocks from the Iberian Massif or Variscan granitoid rocks. A phylogenetic analysis of the members of the family Sironidae using four molecular markers, despite not including all of the Iberian genera, clearly shows the non‐monophyly of the Iberian Cyphophthalmi, indicating that the Iberian Peninsula is home to multiple ancient lineages of mite harvestmen. The two Paramiopsalis species form a sister clade to the Balkan genus Cyphophthalmus, whereas Parasiro constitutes the first lineage of the sironids represented.     

Patterns of Below- and Aboveground Biomass in Eucalyptus populnea Woodland Communities of Northeast Australia along a Rainfall Gradient

In vegetated terrestrial ecosystems, carbon in below- and aboveground biomass (BGB, AGB) often constitutes a significant component of total-ecosystem carbon stock. Because carbon in the BGB is difficult to measure, it is often estimated using BGB to AGB ratios. However, this ratio can change markedly along resource gradients, such as water availability, which can lead to substantial errors in BGB estimates. In this study, BGB and AGB sampling was carried out in Eucalyptus populnea-dominated woodland communities of northeast Australia to examine patterns of BGB to AGB ratio and vertical root distribution at three sites along a rainfall gradient (367, 602, and 1,101 mm). At each site, a vegetation inventory was undertaken on five transects (100 × 4 m), and trees representing the E. populnea vegetation structure were harvested and excavated to measure aboveground and coarse-root (diameter of at least 15 mm) biomass. Biomass of fine and small roots (diameter less than 15 mm) at each site was estimated from 40 cores sampled to 1 m depth. The BGB to AGB ratio of E. populnea-dominated woodland plant communities declined from 0.58 at the xeric end to 0.36 at the mesic end of the rainfall gradient. This was due to a marked decline in AGB with increased aridity whereas the BGB was relatively stable. The vertical distribution of fine roots in the top 1 m of soil varied along the rainfall gradient. The mesic sites had more fine-root biomass (FRB) in the upper soil profile and less at depth than the xeric site. Accordingly, at the xeric site, a much larger proportion of FRB was found at depth compared to the mesic sites. The vertical distribution patterns of small roots of the E. populnea woodland plant communities were consistently )-shaped, with the highest biomass occurring at 15–30-cm depth. The potential significance of such a rooting pattern for grass–tree and shrub–tree co-existence in these ecosystems is discussed. Overall, our results revealed marked changes in BGB to AGB ratio of E. populnea woodland communities along a rainfall gradient. Because E. populnea woodlands cover a large area (96 M ha), their contribution to continental-scale carbon sequestration and greenhouse gas emission can be substantial. Use of the rainfall-zone-specific ratios found in this study, in lieu of a single generic ratio for the entire region, will significantly improve estimates of BGB carbon stocks in these woodlands. In the absence of more specific data, our results will also be relevant in other regions with similar vegetation and rainfall gradients (that is, arid and semiarid woodland ecosystems).     

Developing a realistic sexual network model of chlamydia transmission in Britain

Background  

A national chlamydia screening programme is currently being rolled out in the UK and other countries. However, much of the epidemiology remains poorly understood. In this paper we present a stochastic, individual based, dynamic sexual network model of chlamydia transmission and its parameterisation. Mathematical models provide a theoretical framework for understanding the key epidemiological features of chlamydia: sexual behaviour, health care seeking and transmission dynamics.     

Archaeological mitogenomes illuminate the historical ecology of sea otters (Enhydra lutris) and the viability of reintroduction

Genetic analyses are an important contribution to wildlife reintroductions, particularly in the modern context of extirpations and ecological destruction. To address the complex historical ecology of the sea otter (Enhydra lutris) and its failed 1970s reintroduction to coastal Oregon, we compared mitochondrial genomes of pre-extirpation Oregon sea otters to extant and historical populations across the range. We sequenced, to our knowledge, the first complete ancient mitogenomes from archaeological Oregon sea otter dentine and historical sea otter dental calculus. Archaeological Oregon sea otters (n = 20) represent 10 haplotypes, which cluster with haplotypes from Alaska, Washington and British Columbia, and exhibit a clear division from California haplotypes. Our results suggest that extant northern populations are appropriate for future reintroduction efforts. This project demonstrates the feasibility of mitogenome capture and sequencing from non-human dental calculus and the diverse applications of ancient DNA analyses to pressing ecological and conservation topics and the management of at-risk/extirpated species.