mTOR Inhibition Prevents Epithelial Stem Cell Senescence and Protects from Radiation-Induced Mucositis

The integrity of the epidermis and mucosal epithelia is highly dependent on resident self-renewing stem cells, which makes them vulnerable to physical and chemical insults compromising the repopulating capacity of the epithelial stem cell compartment. This is frequently the case in cancer patients receiving radiation or chemotherapy, many of whom develop mucositis, a debilitating condition involving painful and deep mucosal ulcerations. Here, we show that inhibiting the mammalian target of rapamycin (mTOR) with rapamycin increases the clonogenic capacity of primary human oral keratinocytes and their resident self-renewing cells by preventing stem cell senescence. This protective effect of rapamycin is mediated by the increase in expression of?mitochondrial superoxide dismutase (MnSOD), and the consequent inhibition of ROS formation and oxidative stress. mTOR inhibition also protects from the loss of proliferative basal epithelial stem cells upon ionizing radiation in?vivo, thereby preserving the integrity of the oral mucosa and protecting from radiation-induced mucositis.     

Correlation between trochlear groove depth and patellar position during open and closed kinetic chain exercises in subjects with anterior knee pain

The purpose of this study was to correlate the trochlear shape and patellar tilt angle and lateral patellar displacement at rest and maximal voluntary isometric contraction (MVIC) exercises during open (OKC) and closed kinetic chain (CKC) in subjects with and without anterior knee pain. Subjects were all women, 20 who were clinically healthy and 19 diagnosed with anterior knee pain. All subjects were evaluated and subjected to magnetic resonance exams during OKC and CKC exercise with the knee placed at 15, 30, and 45 degrees of flexion. The parameters evaluated were sulcus angle, patellar tilt angle and patellar displacement using bisect offset. Pearson's r coefficient was used, with p < .05. Our results revealed in knee pain group during CKC and OKC at 15 degrees that the increase in the sulcus angle is associated with a tilt increase and patellar lateral displacement. Comparing sulcus angle, patellar tilt angle and bisect offset values between MVIC in OKC and CKC in the knee pain group, it was observed that patellar tilt angle increased in OKC only with the knee flexed at 30 degrees. Based on our results, we conclude that reduced trochlear depth is correlated with increased lateral patellar tilt and displacement during OKC and CKC at 15 degrees of flexion in people with anterior knee pain. By contrast, 30 degrees of knee flexion in CKC is more recommended in rehabilitation protocols because the patella was more stable than in other positions.     

Phylogenetic Patterns of Geographical and Ecological Diversification in the Subgenus Drosophila

Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. Members of the subgenus Drosophila are distributed across the globe and show a large diversity of ecological niches. Furthermore, taxonomic classification of Drosophila includes the rank radiation, which refers to closely related species groups. Nevertheless, it has never been tested if these taxonomic radiations correspond to evolutionary radiations. Here we present a study of the patterns of diversification of Drosophila to test for increased diversification rates in relation to the geographic and ecological diversification processes. For this, we have estimated and dated a phylogeny of 218 species belonging to the major species groups of the subgenus. The obtained phylogenies are largely consistent with previous studies and indicate that the major groups appeared during the Oligocene/Miocene transition or early Miocene, characterized by a trend of climate warming with brief periods of glaciation. Ancestral reconstruction of geographic ranges and ecological resource use suggest at least two dispersals to the Neotropics from the ancestral Asiatic tropical disribution, and several transitions to specialized ecological resource use (mycophagous and cactophilic). Colonisation of new geographic regions and/or of new ecological resources can result in rapid species diversification into the new ecological niches available. However, diversification analyses show no significant support for adaptive radiations as a result of geographic dispersal or ecological resource shift. Also, cactophily has not resulted in an increase in the diversification rate of the repleta and related groups. It is thus concluded that the taxonomic radiations do not correspond to adaptive radiations.     

Structure-anti-leukemic activity relationship study of ortho-dihydroxycoumarins in U-937 cells: Key role of the δ-lactone ring in determining differentiation-inducing potency and selective pro-apoptotic action

Previous studies indicated the need of at least one phenolic hydroxyl group in the coumarin core for induction of cytotoxicity in different cell lines. Herein, we present an exhaustive structure-activity relationship study including ortho-dihydroxycoumarins (o-DHC) derivatives, cinnamic acid derivatives (as open-chain coumarin analogues) and 1,2-pyrones (representative of the δ-lactone ring of the coumarin core), carried out to further identify the structural features of o-DHC required to induce leukemic cell differentiation and apoptosis in U-937 cells. Our results show for the first time that the δ-lactone ring positively influences the aforementioned biological effects, by conferring greater potency to compounds with an intact coumarin nucleus. Most tellingly, we reveal herein the crucial role of this molecular portion in determining the selective toxicity that o-DHC show for leukemic cells over normal blood cells. From a pharmacological perspective, our findings point out that o-DHC may be useful prototypes for the development of novel chemotherapeutic agents.     

Diversity patterns and activity of uncultured marine heterotrophic flagellates unveiled with pyrosequencing

Flagellated heterotrophic microeukaryotes have key roles for the functioning of marine ecosystems as they channel large amounts of organic carbon to the upper trophic levels and control the population sizes of bacteria and archaea. Still, we know very little on the diversity patterns of most groups constituting this evolutionary heterogeneous assemblage. Here, we investigate 11 groups of uncultured flagellates known as MArine STramenopiles (MASTs). MASTs are ecologically very important and branch at the base of stramenopiles. We explored the diversity patterns of MASTs using pyrosequencing (18S rDNA) in coastal European waters. We found that MAST groups range from highly to lowly diversified. Pyrosequencing (hereafter ‘454'') allowed us to approach to the limits of taxonomic diversity for all MAST groups, which varied in one order of magnitude (tens to hundreds) in terms of operational taxonomic units (98% similarity). We did not evidence large differences in activity, as indicated by ratios of DNA:RNA-reads. Most groups were strictly planktonic, although we found some groups that were active in sediments and even in anoxic waters. The proportion of reads per size fraction indicated that most groups were composed of very small cells (∼2–5 μm). In addition, phylogenetically different assemblages appeared to be present in different size fractions, depths and geographic zones. Thus, MAST diversity seems to be highly partitioned in spatial scales. Altogether, our results shed light on these ecologically very important but poorly known groups of uncultured marine flagellates.     

C. elegans telomeres contain G-strand and C-strand overhangs that are bound by distinct proteins

Single-strand extensions of the G strand of telomeres are known to be critical for chromosome-end protection and length regulation. Here, we report that in C. elegans, chromosome termini possess 3' G-strand overhangs as well as 5' C-strand overhangs. C tails are as abundant as G tails and are generated by a well-regulated process. These two classes of overhangs are bound by two single-stranded DNA binding proteins, CeOB1 and CeOB2, which exhibit specificity for G-rich or C-rich telomeric DNA. Strains of worms deleted for CeOB1 have elongated telomeres as well as extended G tails, whereas CeOB2 deficiency leads to telomere-length heterogeneity. Both CeOB1 and CeOB2 contain OB (oligo-saccharide/oligo-nucleotide binding) folds, which exhibit structural similarity to the second and first OB folds of the mammalian telomere binding protein hPOT1, respectively. Our results suggest that C. elegans telomere homeostasis relies on a novel mechanism that involves 5' and 3' single-stranded termini.     

Nicotinic acetylcholine receptor is internalized via a Rac-dependent, dynamin-independent endocytic pathway

Endocytosis of the nicotinic acetylcholine receptor (AChR) is a proposed major mechanism of neuromodulation at neuromuscular junctions and in the pathology of synapses in the central nervous system. We show that binding of the competitive antagonist alpha-bungarotoxin (alphaBTX) or antibody-mediated cross-linking induces the internalization of cell surface AChR to late endosomes when expressed heterologously in Chinese hamster ovary cells or endogenously in C2C12 myocytes. Internalization occurs via sequestration of AChR-alphaBTX complexes in narrow, tubular, surface-connected compartments, which are indicated by differential surface accessibility of fluorescently tagged alphaBTX-AChR complexes to small and large molecules and real-time total internal reflection fluorescence imaging. Internalization occurs in the absence of clathrin, caveolin, or dynamin but requires actin polymerization. alphaBTX binding triggers c-Src phosphorylation and subsequently activates the Rho guanosine triphosphatase Rac1. Consequently, inhibition of c-Src kinase activity, Rac1 activity, or actin polymerization inhibits internalization via this unusual endocytic mechanism. This pathway may regulate AChR levels at ligand-gated synapses and in pathological conditions such as the autoimmune disease myasthenia gravis.     

Polymeric particles conjugated with a ligand to VCAM-1 exhibit selective, avid, and focal adhesion to sites of atherosclerosis

The increased expression of VCAM-1 on endothelial segments within plaque regions could be used as a target to deliver polymeric drug carriers selectively to sites of atherosclerosis. We probed the hypothesis that polymeric particles conjugated with a ligand for VCAM-1 exhibit selective and avid adhesion to sites of atherosclerosis. Particles made from polystyrene or the biodegradable polymer poly(sebacic acid)-block-polyethylene glycol (PSA-PEG) were conjugated with an antibody to VCAM-1 (alpha-VCAM-1) or IgG (negative control). The particles were injected into the jugular vein of ApoE(-/-) (a murine model of atherosclerosis) or wild type mice and their adhesion to the aorta determined. alpha-VCAM-1 particles exhibited significantly greater adhesion to ApoE(-/-) mouse aorta [32 +/- 5 (mean +/- SEM) particles/mm(2) for polystyrene particles and 31 +/- 7 particles/mm(2) for PSA-PEG particles] compared to the level of adhesion to wild type mouse aorta (18 +/- 1 particles/mm(2) for polystyrene particles and 6 +/- 1 particles/mm(2) for PSA-PEG particles). Within ApoE(-/-) mice, the alpha-VCAM-1 particles exhibited significantly greater adhesion to the aorta (32 +/- 5 particles/mm(2) for polystyrene particles and 31 +/- 7 particles/mm(2) for PSA-PEG particles) compared to the adhesion of IgG particles (1 +/- 1 particles/mm(2) for polystyrene particles and 2 +/- 1 particles/mm(2) for PSA-PEG particles). Detailed analysis of the adhesion revealed that alpha-VCAM-1 particles exhibited focal adhesion to plaque regions, in particular the periphery of the plaques, within the ApoE(-/-) mouse aorta. Combined the data demonstrate that polymeric particles conjugated with a ligand to VCAM-1 exhibit selective, avid and focal adhesion to sites of atherosclerosis providing strong evidence that VCAM-1 ligand bearing polymeric particles could be used for targeting drugs selectively to atherosclerotic tissue.     

Field performance of artificial seed-derived sugarcane plants

This study shows the behaviour of sugarcane plants cv. CP-5243 derived from artificial seed compared with traditional and isolated bud methods. Artificial seed-acclimatised plants were planted in field conditions simultaneously with two-control treatments previously germinated: macropropagated plants derived from stems of three buds and axillary buds isolated from field-grown plants. Plants from artificial seed were taller and had a smaller diameter at 8 months, but these differences disappeared at 12 months. With respect to sugar analysis and yield, no differences in all parameters evaluated were found between artificial seed-derived plants and plants derived from the two other methods.