Occurrence and effects of symbiotic pedunculate barnacles on echinoid hosts

info:eu-repo/semantics/published

No evidence of host specialization in a parasitic pea-crab exploiting two echinoid hosts

The pinnotherid crab Dissodactylus primitivus lives parasitically on 2 burrowingechinoid species, Meoma ventricosa and Plagiobrissus grandis. The fecundity of female crabsvaries between hosts, and is higher when parasitizing P. grandis than M. ventricosa. Moreover, thehosts present great variations in morphology (size and density of spines). These characteristicssuggest the potential to differentiate crabs according to host species. We investigated the genetic(microsatellites) and morphometric (outline analysis) differentiation of this parasitic crab between2 host species at 1 Jamaican site (Western Lagoon, Discovery Bay), and compared it with geographicdifferentiation among 4 sites along the north coast of Jamaica. Greater genetic differencesbetween parasites of the 2 sympatric hosts than between parasites of a single host at different geographiclocations would indicate host differentiation. Genetic analyses (microsatellites) did notdetect spatial differentiation (probably due to local hydrography) or differentiation according tohost species. This lack of host differentiation could be explained by mobility of adult crabsbetween hosts. However, there was weak but significant morphological differentiation betweenfemale crabs from the 2 hosts. This morphological difference may reflect constraints due to hostmorphology.

CB1 cannabinoid receptor deficiency promotes cardiac remodeling induced by pressure overload in mice

Background: The endocannabinoid system is known to play a role in regulating myocardial contractility, but the influence of cannabinoid receptor 1 (CB1) deficiency on chronic heart failure (CHF) remains unclear. In this study we attempted to investigate the effect of CB1 deficiency on CHF induced by pressure overload and the possible mechanisms involved. Methods and results: A CHF model was created by transverse aortic constriction (TAC) in both CB1 knockout mice and wild-type mice. CB1 knockout mice showed a marked increase of mortality due to CHF from 4 to 8 weeks after TAC (p = 0.021). Five weeks after TAC, in contrast to wild-type mice, CB1 knockout mice had a higher left ventricular (LV) end-diastolic pressure, lower rate of LV pressure change (± dp/dt max), lower LV contractility index, and a larger heart weight to body weight ratio and lung weight to body weight ratio compared with wild-type mice (all p < 0.05-0.001). Phosphorylation of the epidermal growth factor receptor (EGFR) and mitogen-activated protein kinases (P38 and ERK) was higher in CB1 knockout mice than that in wild-type mice. In cultured neonatal rat cardiomyocytes, a CB1 agonist reduced cAMP production stimulated by isoproterenol or forskolin, and suppressed phosphorylation of the EGFR, P38, and ERK, while the inhibitory effect of a CB1 agonist on EGFR phosphorylation was abrogated by CB1 knockdown. Conclusion: These findings indicate that cannabinoid receptor 1 inactivation promotes cardiac remodeling by enhancing the activity of the epidermal growth factor receptor and mitogen-activated protein kinases. © 2012 Elsevier Ireland Ltd.

High number of antigen binding cells in unimmunized mice and possible occurrence of multispecific lymphocytes

A high frequency of Tobacco Mosaic virus (TMV) binding cells was found in spleen cells from unimmunized mice (about 3 to 4%). TMV binding is strongly inhibited by previous incubation with anti immunoglobulin antisera. After stripping of membrane receptors, a full recovery for antigen binding capacity can be observed after 24 hr culture. Experiments are presented to exclude artefactual fluorescent cells: interaction of TMV with some non immunoglobulin membrane components; interaction of fluorescent anti TMV antibody with the Fc receptor of B cells; the binding of TMV to cytophilic immunoglobulins. The occurrence of lymphocytes able to bind several non crossreactive antigens is suggested by three lines of evidence: the high number of antigen binding cells in unimmunized mice, presence of surface immunoglobulins on some TMV binding cells after complete capping of TMV receptors and the direct demonstration of lymphocytes binding TMV and hemocyanin at different membrane sites.