Obstructive apneas induce early activation of mesenchymal stem cells and enhancement of endothelial wound healing

Background

The aim was to test the hypothesis that the blood serum of rats subjected to recurrent airway obstructions mimicking obstructive sleep apnea (OSA) induces early activation of bone marrow-derived mesenchymal stem cells (MSC) and enhancement of endothelial wound healing.

Methods

We studied 30 control rats and 30 rats subjected to recurrent obstructive apneas (60 per hour, lasting 15 s each, for 5 h). The migration induced in MSC by apneic serum was measured by transwell assays. MSC-endothelial adhesion induced by apneic serum was assessed by incubating fluorescent-labelled MSC on monolayers of cultured endothelial cells from rat aorta. A wound healing assay was used to investigate the effect of apneic serum on endothelial repair.

Results

Apneic serum showed significant increase in chemotaxis in MSC when compared with control serum: the normalized chemotaxis indices were 2.20 ± 0.58 (m ± SE) and 1.00 ± 0.26, respectively (p < 0.05). MSC adhesion to endothelial cells was greater (1.75 ± 0.14 -fold; p < 0.01) in apneic serum than in control serum. When compared with control serum, apneic serum significantly increased endothelial wound healing (2.01 ± 0.24 -fold; p < 0.05).

Conclusions

The early increases induced by recurrent obstructive apneas in MSC migration, adhesion and endothelial repair suggest that these mechanisms play a role in the physiological response to the challenges associated to OSA.

     

Random Texts Do Not Exhibit the Real Zipf's Law-Like Rank Distribution

Background

Zipf''s law states that the relationship between the frequency of a word in a text and its rank (the most frequent word has rank , the 2nd most frequent word has rank ,…) is approximately linear when plotted on a double logarithmic scale. It has been argued that the law is not a relevant or useful property of language because simple random texts - constructed by concatenating random characters including blanks behaving as word delimiters - exhibit a Zipf''s law-like word rank distribution.

Methodology/Principal Findings

In this article, we examine the flaws of such putative good fits of random texts. We demonstrate - by means of three different statistical tests - that ranks derived from random texts and ranks derived from real texts are statistically inconsistent with the parameters employed to argue for such a good fit, even when the parameters are inferred from the target real text. Our findings are valid for both the simplest random texts composed of equally likely characters as well as more elaborate and realistic versions where character probabilities are borrowed from a real text.

Conclusions/Significance

The good fit of random texts to real Zipf''s law-like rank distributions has not yet been established. Therefore, we suggest that Zipf''s law might in fact be a fundamental law in natural languages.     

Transposable elements in Coffea (Gentianales: Rubiacea) transcripts and their role in the origin of protein diversity in flowering plants

Transposable elements are major components of plant genomes and they influence their evolution, acting as recombination hot spots, acquiring specific cell functions or becoming part of protein-coding regions. The latter is the subject of the present analysis. This study is a report on the annotation of transposable elements (TEs) in expressed sequences of Coffea arabica, Coffea canephora and Coffea racemosa, showing the occurrence of 383 ESTs and 142 unigenes with TE fragments in these three Coffea species. Based on selected unigenes, it was possible to suggest 26 putative proteins with TE-cassette insertions, demonstrating a likely contribution to protein variability. The genes for two of those proteins, the fertility restorer (FR) and the pyrophosphate-dependent phosphofructokinase (PPi-PFKs) genes, were selected for evaluating the impact of TE-cassettes on host gene evolution of other plant genomes (Arabidopsis thaliana, Oryza sativa and Populus trichocarpa). This survey allowed identifying a FR gene in O. sativa harboring multiple insertions of LTR retrotransposons that originated new exons, which however does not necessarily mean a case of molecular domestication. A possible transduction event of a fragment of the PPi-PFK beta-subunit gene mediated by Helitron ATREPX1 in Arabidopsis thaliana was also highlighted.     

Differential regulation of dendrite complexity by AMPA receptor subunits GluR1 and GluR2 in motor neurons

Activity-dependent developmental mechanisms in many regions of the central nervous system are thought to be responsible for shaping dendritic architecture and connectivity, although the molecular mechanisms underlying these events remain obscure. Since AMPA glutamate receptors are developmentally regulated in spinal motor neurons, we have investigated the role of activation of AMPA receptors in dendritic outgrowth of spinal motor neurons by overexpression of two subunits, GluR1 and GluR2, and find that dendrite outgrowth is differentially controlled by expression of these subunits. Overexpression of GluR1 was associated with greater numbers of filopodia, and an increase in the length and complexity of dendritic arbor. In contrast, GluR2 expression did not alter dendritic complexity, but was associated with a moderate increase in length of arbor, and decreased numbers of filopodia. Neither GluR1 nor GluR2 had any effect on the motility of filopodia. In addition, GluR1 but not GluR2 expression increased the density of dendritic puncta incorporating a GFP-labeled PSD95, suggesting that GluR1 may mediate its effect in part by augmenting the number of excitatory synapses within motor neuron dendrites. Together these results suggest that in spinal motor neurons, AMPA receptors composed of GluR1 subunits may facilitate neurotrophic mechanisms in these neurons, permitting sustained dendrite outgrowth and synaptogenesis, whereas expression of AMPA receptors containing GluR2 acts to preserve existing dendritic arbor. Thus, the observed downregulation of GluR1 in motor neurons during postnatal development may limit the formation of new dendrite segments and synapses, promoting stabilized synaptic connectivity.     

Solid-phase peptide synthesis using Nα-trityl-amino acids

Summary The preparation of N^α-trityl-amino acids is described. Several derivatives of trifunctional amino acids carrying acid-and base-labile side-chain protecting groups and the trityl group at the N^α position are prepared for first time. The incorporation of N^α-trityl-amino acids into peptide sequences using solid-phase protocols was achieved. The use of the trityl group for the protection of the α-amino group in conjunction with base-labile side-chain protecting groups constitutes a new method for the assembly of peptides in mild conditions.     

Application of Denaturing Gradient Gel Electrophoresis (DGGE) To Study the Diversity of Marine Picoeukaryotic Assemblages and Comparison of DGGE with Other Molecular Techniques

We used denaturing gradient gel electrophoresis (DGGE) to study the diversity of picoeukaryotes in natural marine assemblages. Two eukaryote-specific primer sets targeting different regions of the 18S rRNA gene were tested. Both primer sets gave a single band when used with algal cultures and complex fingerprints when used with natural assemblages. The reproducibility of the fingerprints was estimated by quantifying the intensities of the same bands obtained in independent PCR and DGGE analyses, and the standard error of these estimates was less than 2% on average. DGGE fingerprints were then used to compare the picoeukaryotic diversity in samples obtained at different depths and on different dates from a station in the southwest Mediterranean Sea. Both primer sets revealed significant differences along the vertical profile, whereas temporal differences at the same depths were less marked. The phylogenetic composition of picoeukaryotes from one surface sample was investigated by excising and sequencing DGGE bands. The results were compared with an analysis of a clone library and a terminal restriction fragment length polymorphism fingerprint obtained from the same sample. The three PCR-based methods, performed with three different primer sets, revealed very similar assemblage compositions; the same main phylogenetic groups were present at similar relative levels. Thus, the prasinophyte group appeared to be the most abundant group in the surface Mediterranean samples as determined by our molecular analyses. DGGE bands corresponding to prasinophytes were always found in surface samples but were not present in deep samples. Other groups detected were prymnesiophytes, novel stramenopiles (distantly related to hyphochytrids or labyrinthulids), cryptophytes, dinophytes, and pelagophytes. In conclusion, the DGGE method described here provided a reasonably detailed view of marine picoeukaryotic assemblages and allowed tentative phylogenetic identification of the dominant members.     

Study of the interaction between the G-quadruplex-forming thrombin-binding aptamer and the porphyrin 5,10,15,20-tetrakis-(N-methyl-4-pyridyl)-21,23H-porphyrin tetratosylate

The G-quadruplex DNA structure has been suggested to be a potential target for anticancer therapies. Therefore, there is increasing interest in the development of drugs that could modulate the stability of G-quadruplex structures. In the current work, the interaction between the thrombin-binding aptamer (TBA, 5′-GGT TGG TGT GGT TGG-3′), which can form an intramolecular G-quadruplex structure, and the porphyrin 5,10,15,20-tetrakis-(N-methyl-4-pyridyl)-21,23H-porphyrin tetratosylate (TmPyP4) was studied. The application of a high-performance liquid chromatography-photodiode array (HPLC-PDA) detector-based method to study this kind of interaction was tested. Molecular absorption data recorded along the chromatographic runs were analyzed by means of multivariate data analysis methods. Moreover, biospecific interaction analysis (BIA) by surface plasmon resonance (SPR) and melting and mole ratio experiments monitored by UV-visible molecular absorption and circular dichroism spectroscopies, were applied to confirm and expand the chromatographic studies. The results showed the formation of an interaction complex with a stoichiometry 1:1 (TmPyP4/TBA) and logarithm of the equilibrium constant equal to 5.7 ± 0.2. Melting and circular dichroism data reflected that the initial G-quadruplex structure of TBA is stabilized in the interaction complex, being slightly distorted by the presence of the ligand.