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The small-scale impact of submerged vegetation (locally enhanced water transparency) on abiotic / biotic parameters was studied in a shallow (

In shallow aquatic ecosystems, wave-induced water motions affect the whole water column down to the sediment. To estimate the influence of these motions on short-term sedimentation rates (SR) in a shallow wind-exposed lagoon, we used plate traps (PTs) which, in contrast to cylindrical traps (CTs), allow trapped matter to become resuspended. In a series of experiments, we varied distance to the sediments, water depth, incubation time, and studied the SRs of total suspended matter and of suspended organic matter at varying conditions of wave exposure. The coefficient of variation of SRs did not change with incubation time. While SRs were similar on both trap types at very low wave exposure, they decreased with increasing wave exposure on the PTs probably due to instantaneous resuspension. In the CTs, SRs increased with increasing wave exposure. This resulted in about 55 times higher SRs in the CTs than on the PTs at high wave exposure. We conclude that CTs are not suitable to estimate natural SRs in wave-affected waters as they overestimate SRs. Our results indicate that SR obtained by PTs, which were here used for the first time in a wind-exposed, non-tidal ecosystem, are a far better estimate for natural short-term SRs.

Migration and proliferation of medial smooth muscle cells (SMC) in the arterial intima contributes to the development of atherosclerotic plaques and restenotic processes after coronary angioplasty. Prostacyclin (PGI 2 )-mediated stimulation of cyclic adenosine 3′5′-monophosphate (cAMP) signaling is believed to be important for maintaining SMC in a quiescent state. In order to identify new cellular targets of PGI 2 /cAMP action, we have used microarray screening to examine changes in the transcriptional profile in human vascular SMC in response to exposure to the stable PGI 2 mimetic iloprost. We have identified 83 genes with significantly altered expression after iloprost (100 nM) exposure for 6 hr. Fifty-one genes were upregulated, among them stanniocalcin precursor (18.8±2.7), zinc finger transcription factor (7.8±2.0), hyaluronan synthase 2 (6.8±1.8), cyclooxygenase 2 (4.7±0.8), dual specific phosphatase (3.9±0.5) and vascular endothelial growth factor (2.3±0.4). Thirty-two genes were reduced, among them cystein-rich angiogenic protein (−14.9±1.3), monocyte chemotactic protein 1 (−7.4±1.1) and plasminogen activator inhibitor PAI-1 (−4.5±0.5). By means of semi-quantitative RT-PCR, time-courses of gene expression were established. The present study identified genes not hitherto recognized to be targets of PGI 2 action, providing further insight into its cAMP-mediated effects on SMC growth, migration and matrix secretion.

Small RNAs ranging in size between 20 and 30 nucleotides are involved in different types of regulation of gene expression including mRNA degradation, translational repression, and chromatin modification. Here we describe the small RNA profile of Drosophila melanogaster as a function of development. We have cloned and sequenced over 4000 small RNAs, 560 of which have the characteristics of RNase III cleavage products. A nonredundant set of 62 miRNAs was identified. We also isolated 178 repeat-associated small interfering RNAs (rasiRNAs), which are cognate to transposable elements, satellite and microsatellite DNA, and Suppressor of Stellate repeats, suggesting that small RNAs participate in defining chromatin structure. rasiRNAs are most abundant in testes and early embryos, where regulation of transposon activity is critical and dramatic changes in heterochromatin structure occur.

Prostacyclin and its mimetics have repeatedly been shown to act antiatherogenic and to inhibit neointima formation in several animal models of vascular injury. Treatment of human vascular smooth muscle cells with the prostacyclin mimetic iloprost (100 nm) drastically reduces expression of Cyr61, encoding the growth-regulatory cystein-rich angiogenic protein, without affecting the degradation rate of Cyr61 mRNA. Thrombin-induced Cyr61 expression was inhibited completely in the presence of iloprost. It is concluded that vasoprotective actions of prostacyclin in vivo may in part be due to inhibition of expression of the growth regulatory gene Cyr61 at sites of vascular lesions.

Persistent stimulation of the Gs protein-coupled prostacyclin receptor (IP-R) causes its slow desensitization in a variety of cell types, a significant desensitization requiring several hours. To evaluate the role of the human IP-R C-terminus in desensitization and agonist-induced internalization, a C-terminally truncated hIP-receptor was generated. The C-terminal 68 amino acid residues were deleted by introduction of a stop codon for exchange of the original S319 codon (termed D318 mutant). Wild-type (WT) and truncated receptor were expressed in COS1 cells. Pretreatment of cells with the stable prostacyclin mimetic cicaprost (200 nM) desensitized cAMP production via WT and D318 receptors to similar extents. The cAMP response of WT and D318, respectively, was reduced by approximately 50% of maximal cAMP formation after 8 hr of continuous agonist stimulation, indicating significant long-term desensitization. Moreover, agonist-promoted sequestration of WT and D318 C-terminally tagged with green fluorescent protein was demonstrated, indicating that receptor internalization was not prevented by truncation of the C-terminus. These results demonstrated that long-term desensitization and sequestration of hIP-R did not depend on structures located in the hIP-R C-terminus.

Prostaglandin-endoperoxide synthase-2 (PGH-synthase) or cyclooxygenase-2 (COX-2) is inducible by a variety of stimuli, e.g. inflammatory mediators, growth factors and hormones and is believed to be responsible for the majority of inflammatory prostanoid production. Moreover, it has been demonstrated that COX-2 contributes substantially to prostacyclin-synthesis in patients with atherosclerosis. In this study, we demonstrate an up-regulation of COX-2 mRNA, protein and product formation by the prostacyclin-mimetic iloprost in human vascular smooth muscle cells (hSMC). COX-2 mRNA expression was induced transiently between 1 and 6 hr and returned to basal levels after 16 hr of iloprost stimulation. COX-2 protein was induced concomitantly between 3 and 6 hr of iloprost stimulation. This was accompanied by an increase in PGI 2 formation. Forskolin, a direct activator of adenylyl cyclase, and dibutyryl cAMP, a cell-permeable cAMP analogue-induced COX-2 mRNA, suggesting a cAMP-dependent COX-2 expression in hSMC. Iloprost-induced COX-2 protein expression and PGI 2 formation was synergistically elevated by co-stimulation with the phorbolester PMA (phorbol-12-myristate-13-acetate). It is concluded, that the observed up-regulation of COX-2 with subsequent release of newly synthesized PGI 2 and the synergistic effect of iloprost and phorbolester on PGI 2 formation provide a positive feedback of prostaglandins on their own synthesizing enzyme. This might be important for control of hSMC proliferation, migration and differentiation as well as inhibition of platelet aggregation.

Bullous pemphigoid (BP), pemphigoid (herpes) gestationis (PG), cicatricial pemphigoid (CP), and lichen planus pemphigoides (LPP) are autoimmune subepidermal bullous diseases that are characterized by circulating autoantibodies to the transmembrane hemidesmosomal protein BP180/type XVII collagen. Previous studies demonstrated that the majority of patients with BP, PG, and LPP show antibodies to an immunodominant, membrane-proximal non-collagenous domain (NC16A) on the extracellular portion of BP180. By the use of non-overlapping peptides of the NC16A domain, we previously demonstrated that autoantibodies from BP and PG patients mainly react with epitopes clustered within the N-terminus of this immunodominant site of BP180; antibodies from patients with LPP also recognized the C-terminal portion of NC16A. However, some of these results had been obtained indirectly by preadsorption studies. The aim of the present study was to analyze the fine specificity of IgG autoantibodies to NC16A in sera from patients with CP and to compare their reactivity with antibodies from BP, PG, and LPP patients using a series of new overlapping fragments covering the entire NC16A domain. We confirm that BP and PG sera mainly react with N-terminal epitopes of NC16A, whereas sera from patients with LPP also bind to C-terminal portions, of this domain. Interestingly, out of ten patients with CP, the sera of seven reacted with NC16A; within NC16A, these sera bound to both C-terminal fragments and an N-terminal epitope right next to the cell membrane. Our data demonstrate a heterogeneous binding pattern of autoantibodies to BP180 NC16A in patients with CP.

For the EP 3 subtype of prostaglandin E receptors, different C-terminal splice variants are known, which are coupled to distinct heterotrimeric GTP-binding proteins (G-proteins). To test the hypothesis that the C-terminal domain is essential for the G-protein-coupling specificity of the EP 3 receptor, we exchanged the carboxyl-terminal tail of a porcine G i -coupled EP 3 receptor isoform for the corresponding C-terminal part of a G s -coupled prostaglandin receptor. The porcine EP 3 receptor was truncated at a lysine (K 350 ) residue at the end of the seventh transmembrane region, representing the splicing site of the different EP 3 receptor isoforms. The wild-type C-terminus (37 amino acids) was substituted by the C-terminal tail (89 amino acids) of the human I-type prostaglandin receptor (hIP-R). The G-protein coupling of the resulting chimeric receptor protein was studied in transfected Chinese hamster ovary (CHO) cells. Stimulation of the chimeric receptor protein with the EP 3 receptor-specific agonist M&B 28.767 did not increase adenosine 3′,5′-cyclic monophosphate (cAMP) formation but did reduce the forskolin-stimulated cAMP formation, indicating G i coupling. Furthermore, the chimeric receptor did not show constitutive activity as demonstrated for the C-terminally truncated EP 3 receptor. Thus, coupling specificity of the EP 3 receptor is not exclusively mediated by the carboxyl-terminal tail, and constitutive activity of a C-terminally truncated EP 3 receptor can be suppressed by the hIP-R C-terminus.