Enhanced proliferation of cultured human vascular smooth muscle cells linked to increased function of RNA-binding protein HuR

In dividing cells, the RNA-binding protein HuR associates with and stabilizes labile mRNAs encoding proliferative proteins, events that are linked to the increased cytoplasmic presence of HuR. Here, assessment of HuR levels in various vascular pathologies (intimal hyperplasia, atherosclerosis and neointimal proliferation, sclerosis of arterialized saphenous venous graft, and fibromuscular dysplasia) revealed a distinct increase in HuR expression and cytoplasmic abundance within the intima and neointima layers. On the basis of these observations, we postulated a role for HuR in promoting the proliferation of vascular smooth muscle cells. To test this hypothesis directly, we investigated the expression, subcellular localization, and proliferative influence of HuR in human vascular smooth muscle cells (hVSMCs). Treatment of hVSMCs with platelet-derived growth factor increased HuR levels in the cytoplasm, thereby influencing the expression of metabolic, proliferative, and structural genes. Importantly, knockdown of HuR expression by using RNA interference caused a reduction of hVSMC proliferation, both basally and following platelet-derived growth factor treatment. We propose that HuR contributes to regulating hVSMC growth and homeostasis in pathologies associated with vascular smooth muscle proliferation.     

MULTIPLE ROUTES OF SEXUALITY IN ALEXANDRIUM TAYLORI (DINOPHYCEAE) IN CULTURE1

Alexandrium taylori Balech is a cyst‐forming dinoflagellate species responsible for recurrent blooms in Mediterranean coastal waters. The nuclear development of the cells during the sexual cycle and the effect of different external nitrate and phosphate levels were studied. Nuclear fusion of gametes occurred 6–12 h after the complete cytoplasmic fusion. The U‐shaped nuclei fused through the end of one nucleus and the mid‐area of the other. The mobile and biflagellated zygote had a large, U‐shaped nucleus and may follow three different fates: direct division, short‐term encystment (ecdysal), and long‐term encystment (resting). Ecdysal cysts may divide in >24–96 h into two, four, six, or eight cells before germinating. Meiosis presumably occurred in three locations: in the planozygote, within the ecdysal cyst, and in the planomeiocyte (germling) liberated either from ecdysal or resting cysts. The effects of nutrients on these routes were studied in individually isolated sexual stages. (1) Direct divisions occurred mainly under replete conditions (L1), whereas no direct planozygote divisions were recorded in media with no phosphate added (L‐P). (2) Short‐term encystment was larger in media lacking phosphate (L‐P and L/30) than in medium with no nitrate added (L‐N) or under replete conditions (L1). (3) Long‐term encystment was only observed in medium with no nitrate added (L‐N). The long‐lived resting cyst, not previously described for this species, had a clear double wall, an irregular shape, a flat morphology, and a middle orange spot. No cysts germinated in 1–2 months, whereas 86% of the cysts germinated 2–3 months after being formed. A flow cytometry analysis showed that sexual induction and zygote formation were very fast and highly common processes, zygotes being nearly half of the population at days 3 and 5 after the induction of sexuality in the cultures.     

Expression of one sponge Iroquois homeobox gene in primmorphs from Suberites domuncula during canal formation

Sponges (Porifera) represent the evolutionary oldest multicellular animals. They are provided with the basic molecules involved in cell-cell and cell-matrix interactions. We report here the isolation and characterization of a complementary DNA from the sponge Suberites domuncula coding for the sponge homeobox gene, SUBDOIRX-a. The deduced polypeptide with a predicted Mr of 44,375 possesses the highly conserved Iroquois-homeodomain. We applied in situ hybridization to localize Iroquois in the sponge. The expression of this gene is highest in cells adjacent to the canals of the sponge in the medulla region. To study the expression of Iroquois during development, the in vitro primmorph system from S. domuncula was used. During the formation of these three-dimensional aggregates composed of proliferating cells, the expression of Iroquois depends on ferric iron and water current. An increased expression in response to water current is paralleled with the formation of canal-like pores in the primmorphs. It is suggested that Iroquois expression is involved in the formation of the aquiferous system, the canals in sponges and the canal-like structures in primmorphs.     

New Insights into the Phylogeny and Worldwide Dispersion of Two Closely Related Nematode Species,Bursaphelenchus xylophilus and Bursaphelenchus mucronatus

The pinewood nematode, Bursaphelenchus xylophilus, is one of the greatest threats to coniferous forests worldwide, causing severe ecological damage and economic loss. The biology of B. xylophilus is similar to that of its closest relative, B. mucronatus, as both species share food resources and insect vectors, and have very similar morphological characteristics, although little pathogenicity to conifers has been associated with B. mucronatus. Using both nuclear and mitochondrial DNA markers, we show that B. xylophilus and B. mucronatus form distinct phylogenetic groups with contrasting phylogeographic patterns. B. xylophilus presents lower levels of intraspecific diversity than B. mucronatus, as expected for a species that evolved relatively recently through geographical or reproductive isolation. Genetic diversity was particularly low in recently colonised areas, such as in southwestern Europe. By contrast, B. mucronatus displays high levels of genetic diversity and two well-differentiated clades in both mitochondrial and nuclear DNA phylogenies. The lack of correlation between genetic and geographic distances in B. mucronatus suggests intense gene flow among distant regions, a phenomenon that may have remained unnoticed due to the reduced pathogenicity of the species. Overall, our findings suggest that B. xylophilus and B. mucronatus have different demographic histories despite their morphological resemblance and ecological overlap. These results suggest that Bursaphelenchus species are a valuable model for understanding the dispersion of invasive species and the risks posed to native biodiversity and ecosystems.     

Variations in carotenoid content and acyl chain composition in exponential,stationary and biofilm states of Staphylococcus aureus,and their influence on membrane biophysical properties

Bacteria are often found in close association with surfaces, resulting in the formation of biofilms. In Staphylococcus aureus (S. aureus), biofilms are implicated in the resilience of chronic infections, presenting a serious clinical problem world-wide. Here, S. aureus biofilms are grown under flow within clinical catheters at 37 °C. The lipid composition and biophysical properties of lipid extracts from these biofilms are compared with those from exponential growth and stationary phase cells. Biofilms show a reduction in iso and anteiso branching compensated by an increase in saturated fatty acids compared to stationary phase. A drastic reduction in carotenoid levels is also observed during biofilm formation. Thermotropic measurements of Laurdan GP and DPH polarization, show a reduction of lipid packing at 37 °C for biofilms compared to stationary phase. We studied the effects of carotenoid content on DMPG and DPPG model membranes showing trends in thermotropic behavior consistent with those observed in bacterial isolates, indicating that carotenoids participate in modulating lipid packing. Additionally, bending elastic constant (k_c) measurements using vesicle fluctuation analysis (VFA) show that the presence of carotenoids can increase membrane bending rigidity. The antimicrobial peptide Magainin H2 was less activity on liposomes composed of stationary phase compared to biofilms or exponential growth isolates. This study contributes to an understanding of how Staphylococcus aureus modulates the composition of its membrane lipids, and how those changes affect the biophysical properties of membranes, which in turn may play a role in its virulence and its resistance to different membrane-active antimicrobial agents.     

One year of exercise training promotes distinct adaptations in right and left ventricle of female Sprague-Dawley rats

Journal of Physiology and Biochemistry - Aerobic exercise training induces a unique cardioprotective phenotype, but it is becoming clear that it does not promote the same structural, functional,...     

Influence of the geometry around the manganese ion on the peroxidase and catalase activities of Mn(III)-Schiff base complexes

The peroxidase and catalase activities of eighteen manganese-Schiff base complexes have been studied. A correlation between the structure of the complexes and their catalytic activity is discussed on the basis of the variety of systems studied. Complexes 1-18 have the general formulae [MnLⁿ(D)₂](X)(H₂O/CH₃OH)_m, where Lⁿ = L¹-L¹³; D = H₂O, CH₃OH or Cl; m = 0-2.5 and X = NO₃⁻, Cl⁻, ClO₄⁻, CH₃COO⁻, C₂H₅COO⁻ or C₅H₁₁COO⁻. The dianionic tetradentate Schiff base ligands H₂Lⁿ are the result of the condensation of different substituted (OMe-, OEt-, Br-, Cl-) hydroxybenzaldehyde with diverse diamines (1,2-diaminoethane for H₂L¹-H₂L²; 1,2-diamino-2-methylethane for H₂L³-H₂L⁴; 1,2-diamino-2,2-dimethylethane for H₂L⁵; 1,2-diphenylenediamine for H₂L⁶-H₂L⁷; 1,3-diaminopropane for H₂L⁸-H₂L¹¹; 1,3-diamino-2,2-dimethylpropane for H₂L¹²-H₂L¹³). The new Mn(III) complexes [MnL¹(H₂O)Cl](H₂O)_2.5 (2), [MnL²(H₂O)₂](NO₃)(H₂O) (4), [MnL⁶(H₂O)₂][MnL⁶(CH₃OH)(H₂O)](NO₃)₂(CH₃OH) (8), [MnL⁶(H₂O)(OAc)](H₂O) (9) and [MnL⁷(H₂O)₂](NO₃)(CH₃OH)₂ (12) were isolated and characterised by elemental analysis, magnetic susceptibility and conductivity measurements, redox studies, ESI spectrometry and UV, IR, paramagnetic ¹H NMR, and EPR spectroscopies. X-ray crystallographic studies of these complexes and of the ligand H₂L⁶ are also reported. The crystal structures of the rest of the complexes have been previously published and herein we have only revised their study by those techniques still not reported (EPR and ¹H NMR for some of these compounds) and which help to establish their structures in solution. Complexes 1-12 behave as more efficient mimics of peroxidase or catalase in contrast with 13-18. The analysis between the catalytic activity and the structure of the compounds emphasises the significance of the existence of a vacant or a labile position in the coordination sphere of the catalyst.     

Space exploration by dendritic cells requires maintenance of myosin II activity by IP3 receptor 1

Dendritic cells (DCs) patrol the interstitial space of peripheral tissues. The mechanisms that regulate their migration in such constrained environment remain unknown. We here investigated the role of calcium in immature DCs migrating in confinement. We found that they displayed calcium oscillations that were independent of extracellular calcium and more frequently observed in DCs undergoing strong speed fluctuations. In these cells, calcium spikes were associated with fast motility phases. IP₃ receptors (IP₃Rs) channels, which allow calcium release from the endoplasmic reticulum, were identified as required for immature DCs to migrate at fast speed. The IP₃R1 isoform was further shown to specifically regulate the locomotion persistence of immature DCs, that is, their capacity to maintain directional migration. This function of IP₃R1 results from its ability to control the phosphorylation levels of myosin II regulatory light chain (MLC) and the back/front polarization of the motor protein. We propose that by upholding myosin II activity, constitutive calcium release from the ER through IP₃R1 maintains DC polarity during migration in confinement, facilitating the exploration of their environment.     

Altered ATP Hydrolysis Induced by Pentylenetetrazol Kindling in Rat Brain Synaptosomes

The ectonucleotidase pathway is an important metabolic source of extracellular adenosine. Adenosine has potent anticonvulsant effects on various models of epilepsy. One of these models is pentylenetetrazol (PTZ) kindling, in which repeated administration of subconvulsive doses of this drug induces progressive intensification of seizure activity. In this study, we examine the effect of a single convulsive injection (60 mg/kg, i.p.) or 10 successive (35 mg/kg, i.p.) injections of PTZ on synaptosomal ectonucleotidases. Our results have shown that no changes in ectonucleotidase activities were seen at 0, 1, and 24 h or at 5 days after a single convulsive PTZ injection. However, after PTZ-kindling, rats which were more resistant to seizure development presented an increase in ATP hydrolysis in synaptosomes from hippocampus and cerebral cortex (44% and 28%, respectively). These results suggest that changes in nucleotide hydrolysis may represent an important mechanism in the modulation of chronic epileptic activity in this model.