Expression and characterization of hepatocyte growth factor receptor-IgG fusion proteins. Effects of mutations in the potential proteolytic cleavage site on processing and ligand binding.

The receptor for hepatocyte growth factor (HGF) is the product of the c-met proto-oncogene, a membrane-spanning tyrosine kinase receptor. To facilitate analysis of HGF and its receptor (HGFr), we expressed and purified a chimeric protein containing the extracellular domain (ECD) of the HGFr fused to the constant region of IgG heavy chain. This soluble form of the HGFr (sHGFr) bound HGF with an affinity similar to that of the authentic, membrane-associated receptor. The sHGFr also neutralized the binding of HGF to the HGFr expressed on A549 cells. Like the mature form of the HGFr, sHGFr is a heterodimer which arises by proteolytic processing within the ECD. In order to characterize the requirements for proteolytic processing of the ECD and the effects of cleavage on ligand binding, we expressed sHGFr variants containing amino acid substitutions in the putative processing site. Replacement of the P1 or P4 arginine, but not the P3 lysine, with alanine inhibited conversion to the alpha/beta heterodimer. This suggests that maturation is mediated by furin or a furin-like protease. Finally, we showed that processing of the sHGFr into the alpha/beta form is not required for high affinity binding to either pro- or mature HGF.     

Changes in Cannabinoid Receptors,Aquaporin 4 and Vimentin Expression after Traumatic Brain Injury in Adolescent Male Mice. Association with Edema and Neurological Deficit

Traumatic brain injury (TBI) incidence rises during adolescence because during this critical neurodevelopmental period some risky behaviors increase. The purpose of this study was to assess the contribution of cannabinoid receptors (CB1 and CB2), blood brain barrier proteins (AQP4) and astrogliosis markers (vimentin) to neurological deficit and brain edema formation in a TBI weight drop model in adolescent male mice. These molecules were selected since they are known to change shortly after lesion. Here we extended their study in three different timepoints after TBI, including short (24h), early mid-term (72h) and late mid-term (two weeks). Our results showed that TBI induced an increase in brain edema up to 72 h after lesion that was directly associated with neurological deficit. Neurological deficit appeared 24 h after TBI and was completely recovered two weeks after trauma. CB1 receptor expression decreased after TBI and was negatively correlated with edema formation and behavioral impairments. CB2 receptor increased after injury and was associated with high neurological deficit whereas no correlation with edema was found. AQP4 increased after TBI and was positively correlated with edema and neurological impairments as occurred with vimentin expression in the same manner. The results suggest that CB1 and CB2 differ in the mechanisms to resolve TBI and also that some of their neuroprotective effects related to the control of reactive astrogliosis may be due to the regulation of AQP4 expression on the end-feet of astrocytes.     

Contribution of estrogen receptors alpha and beta to the effects of estradiol in the brain

Clinical and experimental studies show a modulatory role of estrogens in the brain and suggest their beneficial action in mental and neurodegenerative diseases. The estrogen receptors ER and ERβ are present in the brain and their targeting could bring selectivity and reduced risk of cancer. Implication of ERs in the effect of estradiol on dopamine, opiate and glutamate neurotransmission is reviewed. The ER agonist, PPT, is shown as estradiol to modulate hippocampal NMDA receptors and AMPA receptors in cortex and striatum of ovariectomized rats whereas the ERβ agonist DPN is inactive. Striatal DPN activity suggests implication of ERβ in estradiol modulation of D2 receptors and transporters in ovariectomized rats and is supported by the lack of effect of estradiol in ERβ knockout (ERKOβ) mice. Both ER and ERβ agonists modulate striatal preproenkephalin (PPE) gene expression in ovariectomized rats. In male mice PPT protects against MPTP toxicity to striatal dopamine; this implicates Akt/GSK3β signaling and the apoptotic regulators Bcl2 and Bad. This suggests a role for ER in striatal dopamine neuroprotection. ERKO mice are more susceptible to MPTP toxicity and not protected by estradiol; differences in ERKOβ mice are subtler. These results suggest therapeutic potential for the brain of ER specific agonists.     

A new species of Heteromyoxyuris (Nematoda: Oxyuridae), parasite of Perognathus flavus (Rodentia: Heteromyidae) from Mexico

Heteromyoxyuris otomii n. sp., which inhabits the intestinal caecum of Perognathus flavus (Heteromyidae), in Zaragoza, Hidalgo, Mexico, is described. This new species differs from the 2 other congeneric species in the morphology and length of lateral alae in males. Heteromyoxyuris deserti has simple lateral alae located at both sides of the body, whereas in the new species, these structures are double at both sides; in contrast, lateral alae of Heteromyoxyuris longejector begin at the posterior half of the body, whereas they arise in the first third in the new species. Heteromyoxyuris longejector was found in 2 new host species, i.e., Perognathus amplus and Chaetodipus hispidus. This record represents the first record for the species in Mexico, increasing its geographic distribution.     

Defining the importance of landscape metrics for large branchiopod biodiversity and conservation: the case of the Iberian Peninsula and Balearic Islands

The deficiency in the distributional data of invertebrate taxa is one of the major impediments acting on the bias towards the low awareness of its conservation status. The present study sets a basic framework to understand the large branchiopods distribution in the Iberian Peninsula and Balearic Islands. Since the extensive surveys performed in the late 1980s, no more studies existed updating the information for the whole studied area. The present study fills the gap, gathering together all available information on large branchiopods distribution since 1995, and analysing the effect of human population density and several landscape characteristics on their distribution, taking into consideration different spatial scales (100 m, 1 km and 10 km). In overall, 28 large branchiopod taxa (17 anostracans, 7 notostracans and 4 spinicaudatans) are known to occur in the area. Approximately 30% of the sites hosted multiple species, with a maximum of 6 species. Significant positive co-occurring species pairs were found clustered together, forming 4 different associations of large branchiopod species. In general, species clustered in the same group showed similar responses to analysed landscape characteristics, usually showing a better fit at higher spatial scales.     

Spatial analysis improves species distribution modelling during range expansion

Species distribution models (SDMs) assume equilibrium between species' distribution and the environment. However, this assumption can be violated under restricted dispersal and spatially autocorrelated environmental conditions. Here we used a model to simulate species' ranges expansion under two non-equilibrium scenarios, evaluating the performance of SDM coupled with spatial eigenvector mapping. The highest fit is for the models that include space, although the relative importance of spatial variables during the range expansion differs in the two scenarios. Incorporating space to the models was important only under colonization-lag non-equilibrium, under the expected scenario. Thus, mechanisms that generate range cohesion and determine species' distribution under climate changes can be captured by spatial modelling, with advantages compared with other techniques and in line with recent claims that SDMs have to account for more complex dynamic scenarios.     

Characterization of reproduction-specific genes in a marine bivalve mollusc: influence of maturation stage and sex on mRNA expression

Numerous studies have investigated the reproduction mechanisms in mollusc species at a biochemical and physiological level; few have described these mechanisms at a molecular level, despite great commercial interest in several mollusc species. We investigated genes involved in gonad maturation of the marine scallop Argopecten purpuratus. A cDNA library was made from gonad tissue. After sequence analysis, 418 unique genes were characterized, of these, about 80% were of unknown function. Among the identified sequences, we analyzed the mRNA expression by real-time PCR of 7 genes involved in reproduction mechanisms, either directly: testis-specific serine/threonine-protein kinase (TSSK), vitellogenin (Vg), and spermatogenesis and centriole associated 1 (SCA) or indirectly: calcineurin A (CNA), centrin, RNA-specific adenosine deaminase (ADAR), and cytidine deaminase (CDA). The real-time PCR analyses were conducted on different tissues of mature and immature scallops (testis, ovary, immature gonad, gill, digestive gland and mantle). The genes studied, presented (1) a strong tissue-dependent expression pattern (higher expression in gonad tissues than in all other tissues) and (2) a sex- and maturation-specific expression pattern (except centrin). This is the first time that the expression of specific genes involved in reproduction mechanisms in a marine mollusc has been described at the molecular level.