Resilience of Zostera marina habitats and response of the macroinvertebrate community to physical disturbance caused by clam harvesting

The consequences of physical disturbances to seagrasses depend on disturbance frequency relative to the capacity for recolonization and recovery following fragmentation. In a subtidal seagrass meadow of Zostera marina L., following a season of clam harvesting, we compared the temporal change of shoot density and biomass of this seagrass together with the community structure of the associated macroinvertebrates, at two sites differing in the intensity of the physical disturbance. The impacted site showed significantly lower shoot density and total biomass than the non-impacted site initially. The increase in above-ground biomass over four months (May to September) of this species was significantly higher (46%) at the impacted site than in the area not affected by the disturbance. Four months after cessation of the extraction activity, the biomass and density values of Z. marina reached similar values to those measured in the non-impacted site. The sexual reproductive effort of the seagrass population affected by the disturbance (4%) was significantly lower than at the non-impacted site (10%), which could influence genetic diversity and the seed bank. The community structure of molluscs showed 54% similarity between sites at the beginning of the study. Four months later, mollusc communities increased to a similarity of 74%. The current closure season (four months annually) established for the recovery of the exploited stocks of bivalves allowed the recovery of Z. marina density and biomass. Nevertheless, other population properties, such as those related to reproductive patterns, remained altered by the disturbance.     

Adenosine A<Subscript>2A</Subscript> receptor regulates expression of vascular endothelial growth factor in feto-placental endothelium from normal and late-onset pre-eclamptic pregnancies

We aim to investigate whether A_2A/nitric oxide-mediated regulation of vascular endothelial growth factor (VEGF) expression is impaired in feto-placental endothelial cells from late-onset pre-eclampsia. Cultures of human umbilical vein endothelial cells (HUVECs) and human placental microvascular endothelial cells (hPMECs) from normal and pre-eclamptic pregnancies were used. Assays by using small interference RNA (siRNA) for A_2A were performed, and transfected cells were used for estimation of messenger RNA (mRNA) levels of VEGF, as well as for cell proliferation and angiogenesis in vitro. CGS-21680 (A_2A agonist, 24 h) increases HUVEC and hPMEC proliferation in a dose response manner. Furthermore, similar to CGS-21680, the nitric oxide donor, S-nitroso-N-acetyl-penicillamine oxide (SNAP), increased cell proliferation in a dose response manner (logEC₅₀ 10^?9.2 M). In hPMEC, CGS-21680 increased VEGF protein levels in both normal (～1.5-fold) and pre-eclamptic pregnancies (～1.2-fold), an effect blocked by the A_2A antagonist, ZM-241385 (10^?5 M) and the inhibitor of NO synthase, N _ω-nitro-L-arginine methyl ester hydrochloride (L-NAME). Subsequently, SNAP partially recovered cell proliferation and in vitro angiogenesis capacity of cells from normal pregnancies exposed to siRNA for A_2A. CGS-21680 also increased (～1.5-fold) the level of VEGF mRNA in HUVEC from normal pregnancies, but not in pre-eclampsia. Additionally, transfection with siRNA for A_2A decrease (～30 %) the level of mRNA for VEGF in normal pregnancy compared to untransfected cells, an effect partially reversed by co-incubation with SNAP. The A_2A-NO-VEGF pathway is present in endothelium from microcirculation and macrocirculation in both normal and pre-eclamptic pregnancies. However, NO signaling pathway seems to be impaired in HUVEC from pre-eclampsia.     

Lesch-Nyhan disease in two families from Chiloé Island with mutations in the HPRT1 gene

Lesch-Nyhan disease (LND) is a rare X-linked inherited neurogenetic disorder of purine metabolism in which the enzyme, hypoxanthine-guanine phosphoribosyltransferase (HGprt) is defective. The authors report two independent point mutations leading to splicing errors: IVS 2 +1G>A, c.134 +1G>A, and IVS 3 +1G>A, c.318 +1G>A in the hypoxanthine-phosphoribosyltransferase1 (HPRT1) gene which result in exclusion of exon 2 and exon 3 respectively, in the HGprt enzyme protein from different members of two Chiloé Island families. Molecular analysis has revealed the heterogeneity of genetic mutation of the HPRT1 gene responsible for the HGprt deficiency. It allows fast, accurate carrier detection and genetic counseling.     

Analysis of Moraxella catarrhalis outer membrane antigens cross-reactive with Neisseria meningitidis and Neisseria lactamica

Mouse sera against outer membrane proteins from Moraxella catarrhalis, Neisseria meningitidis and Neisseria lactamica, and human sera from both healthy individuals and patients convalescing from meningococcal meningitis were used to identify cross-reactive antigens. Mouse anti-N. meningitidis and anti-N. lactamica sera recognized 77, 62 and 32 kDa outer membrane antigens in M. catarrhalis strains; on the contrary, the meningococcal porin PorB (38-42 kDa) was recognized by one of the two anti-M. catarrhalis sera. Human sera from both healthy individuals and patients convalescing from meningococcal meningitis also showed cross-reactive antibodies against these proteins. The existence of cross-reactive antigens in M. catarrhalis and N. meningitidis (as well as in N. lactamica) could favor the development of natural immunization against both pathogens.     

Alteration in mitochondrial Ca<Superscript>2+</Superscript> uptake disrupts insulin signaling in hypertrophic cardiomyocytes

Background

Cardiac hypertrophy is characterized by alterations in both cardiac bioenergetics and insulin sensitivity. Insulin promotes glucose uptake by cardiomyocytes and its use as a substrate for glycolysis and mitochondrial oxidation in order to maintain the high cardiac energy demands. Insulin stimulates Ca²⁺ release from the endoplasmic reticulum, however, how this translates to changes in mitochondrial metabolism in either healthy or hypertrophic cardiomyocytes is not fully understood.

Results

In the present study we investigated insulin-dependent mitochondrial Ca²⁺ signaling in normal and norepinephrine or insulin like growth factor-1-induced hypertrophic cardiomyocytes. Using mitochondrion-selective Ca²⁺-fluorescent probes we showed that insulin increases mitochondrial Ca²⁺ levels. This signal was inhibited by the pharmacological blockade of either the inositol 1,4,5-triphosphate receptor or the mitochondrial Ca²⁺ uniporter, as well as by siRNA-dependent mitochondrial Ca²⁺ uniporter knockdown. Norepinephrine-stimulated cardiomyocytes showed a significant decrease in endoplasmic reticulum-mitochondrial contacts compared to either control or insulin like growth factor-1-stimulated cells. This resulted in a reduction in mitochondrial Ca²⁺ uptake, Akt activation, glucose uptake and oxygen consumption in response to insulin. Blocking mitochondrial Ca²⁺ uptake was sufficient to mimic the effect of norepinephrine-induced cardiomyocyte hypertrophy on insulin signaling.

Conclusions

Mitochondrial Ca²⁺ uptake is a key event in insulin signaling and metabolism in cardiomyocytes.

     

Effects of copper on the fitness of the Chilean scallop Argopecten purpuratus (Mollusca: Bivalvia)

Exposure to high concentrations of metals can affect populations and individuals at morphological, physiological, biochemical or genetic levels. Metal pollution is a source of environmental stress that can have deleterious effects on organisms and generate selective pressure upon populations. This work attempts to establish whether concentrations of copper, above physiological requirements, can affect the genetic structure of a cohort of Chilean scallop Argopecten purpuratus. Following the determination of LC₅₀ for 96 h experiments, other acute toxicity tests were carried out, exposing the juveniles to solutions of 150 ppb copper for 120 h. Dead, surviving and control individuals from these bioassays were genetically characterized for five polymorphic loci, Isocitrate dehydrogenase (Idh), Octopine dehydrogenase (Ocdh), Phosphogluconate dehydrogenase (Pgd), Leucine aminopeptidase (Lap) and Phosphoglucose isomerase (Pgi). Results showed no significant differences in allele and genotypic frequencies between surviving and dead individuals, although for the same groups significant differences were found in estimated mean heterozygosity. Pgi and Ocdh showed significantly different heterozygosity values for dead and surviving individuals. A positive relationship between multilocus heterozygosity and survival was found for young A. purpuratus exposed to high copper concentrations; thus, we found evidence of a differential response to exposure to high copper concentrations, related to degree of heterozygosity.     

Processing and characterization of porous structures from chitosan and starch for tissue engineering scaffolds

Natural biodegradable polymers were processed by different techniques for the production of porous structures for tissue engineering scaffolds. Potato, corn, and sweet potato starches and chitosan, as well as blends of these, were characterized and used in the experiments. The techniques used to produce the porous structures included a novel solvent-exchange phase separation technique and the well-established thermally induced phase separation method. Characterization of the open pore structures was performed by measuring pore size distribution, density, and porosity of the samples. A wide range of pore structures ranging from 1 to 400 microm were obtained. The mechanisms of pore formation are discussed for starch and chitosan scaffolds. Pore morphology in starch scaffolds seemed to be determined by the initial freezing temperature/freezing rate, whereas in chitosan scaffolds the shape and size of pores may have been determined by the processing route used. The mechanical properties of the scaffolds were assessed by indentation tests, showing that the indentation collapse strength depends on the pore geometry and the material type. Bioactivity and degradation of the potential scaffolds were assessed by immersion in simulated body fluid.     

Temporal dynamics of gastropod fauna on subtidal sandy sediments of the Ensenada de Baiona (NW Iberian Peninsula)

The temporal variation of the gastropod fauna inhabiting sandy sediments of the Ensenada de Baiona (Galicia, Spain) was studied at three subtidal sites from February 1996 to February 1997 by means of quantitative sampling. A total of 5,463 individuals representing 51 gastropod species and 22 families were found. The family Pyramidellidae was the most diverse in number of species (11 species), followed by Rissoidae and Trochidae (4 species each). The dogwhelk, Nassarius reticulatus, and the rissoid snail, Rissoa parva, were the numerically dominant species at the three studied sites; those and other abundant species showed their greatest densities by the end of summer and the beginning of autumn. In general, univariate measures of the assemblage (number of species, abundance, diversity and evenness) showed variations through time; greater values were recorded between summer and autumn depending on the site. Multivariate analyses done on abundance data showed certain seasonality in the evolution of the assemblage as expected for shallow subtidal sandy sediments at temperate latitudes; those seasonal changes were mostly related to variations in abundance of numerically dominant species. Although the measured sedimentary variables did not show significant correlations with faunal univariate parameters, sediment heterogeneity due to the presence of mats of Zostera marina L. and shells of dead bivalves might explain the differences in composition of the gastropod assemblage among sampling sites.