Cytoskeletal remodeling in vascular smooth muscle cells in response to angiotensin II-induced activation of the SHP-2 tyrosine phosphatase

Angiotensin II is an octapeptide that regulates diverse cellular responses including the actin cytoskeletal organization. In this study, stable cell lines overexpressing wild-type or catalytically inactive SHP-2 were employed to elucidate the signaling pathway utilized by the SHP-2 tyrosine phosphatase that mediates an angiotensin II-induced reorganization of the actin cytoskeleton in vascular smooth muscle cells (VSMC). The expression of wild-type SHP-2 prevented an angiotensin II dependent increase in stress fiber formation. In contrast, the catalytically inactive mutant SHP-2 increased stress fiber formation. Additional observations further established that SHP-2 regulates the reorganization of the actin cytoskeleton through RhoA- and Vav2-dependent signaling pathways. The expression of wild-type SHP-2 caused a dephosphorylation of several focal adhesion associated proteins including paxillin, p130Cas, and tensin in VSMC. This dephosphorylation of focal adhesion associated proteins was accompanied by significantly decreased numbers of focal adhesions within cells. These results demonstrate a unique role for SHP-2 in the regulation of the cellular architecture of VSMC, suggesting the possibility that this phosphatase might be instrumental in vascular remodeling.     

The tortoise and the hare II: relative utility of 21 noncoding chloroplast DNA sequences for phylogenetic analysis

Chloroplast DNA sequences are a primary source of data for plant molecular systematic studies. A few key papers have provided the molecular systematics community with universal primer pairs for noncoding regions that have dominated the field, namely trnL-trnF and trnK/matK. These two regions have provided adequate information to resolve species relationships in some taxa, but often provide little resolution at low taxonomic levels. To obtain better phylogenetic resolution, sequence data from these regions are often coupled with other sequence data. Choosing an appropriate cpDNA region for phylogenetic investigation is difficult because of the scarcity of information about the tempo of evolutionary rates among different noncoding cpDNA regions. The focus of this investigation was to determine whether there is any predictable rate heterogeneity among 21 noncoding cpDNA regions identified as phylogenetically useful at low levels. To test for rate heterogeneity among the different cpDNA regions, we used three species from each of 10 groups representing eight major phylogenetic lineages of phanerogams. The results of this study clearly show that a survey using as few as three representative taxa can be predictive of the amount of phylogenetic information offered by a cpDNA region and that rate heterogeneity exists among noncoding cpDNA regions.     

Searching for biomarkers of heart failure in the mass spectra of blood plasma

We have developed a technique for analysing blood plasma using MALDI-MS with subsequent data analysis to identify significant and specific differences between heart failure (HF) patients and healthy individuals. A training dataset comprising 100 HF patients and 100 healthy individuals was used to search for biomarkers (m/z range 1000-10,000). EWP cartridges when used in tandem with microcon centrifugal filters were found to give the best results. A data management chain including event binning, background subtraction and feature extraction was developed to reduce the data, and statistical analysis was used to map feature intensities on to a common scale. Various mathematical approaches including a simple cumulative score, support vector machines (SVM) and genetic algorithms (GAs) were then used to combine the results from individual features and provide a robust classification algorithm. The SVM gave the most promising results (accuracy 95%, receiver operating characteristic (ROC) score of 0.997 using 18 selected features). Finally, a test dataset comprising a further 32 HF patients and 20 controls was used to verify that the 18 putative biomarkers and classification algorithms gave reliable predictions (accuracy 88.5%, ROC score 0.998).     

Intra‐floral resource partitioning between endemic and invasive flower visitors: consequences for pollinator effectiveness

1. Sympatric flower visitor species often partition nectar and pollen and thus affect each other's foraging pattern. Consequently, their pollination service may also be influenced by the presence of other flower visiting species. Ants are solely interested in nectar and frequent flower visitors of some plant species but usually provide no pollination service. Obligate flower visitors such as bees depend on both nectar and pollen and are often more effective pollinators. 2. In Hawaii, we studied the complex interactions between flowers of the endemic tree Metrosideros polymorpha (Myrtaceae) and both, endemic and introduced flower‐visiting insects. The former main‐pollinators of M. polymorpha were birds, which, however, became rare. We evaluated the pollinator effectiveness of endemic and invasive bees and whether it is affected by the type of resource collected and the presence of ants on flowers. 3. Ants were dominant nectar‐consumers that mostly depleted the nectar of visited inflorescences. Accordingly, the visitation frequency, duration, and consequently the pollinator effectiveness of nectar‐foraging honeybees (Apis mellifera) strongly decreased on ant‐visited flowers, whereas pollen‐collecting bees remained largely unaffected by ants. Overall, endemic bees (Hylaeus spp.) were ineffective pollinators. 4. The average net effect of ants on pollination of M. polymorpha was neutral, corresponding to a similar fruit set of ant‐visited and ant‐free inflorescences. 5. Our results suggest that invasive social hymenopterans that often have negative impacts on the Hawaiian flora and fauna may occasionally provide neutral (ants) or even beneficial net effects (honeybees), especially in the absence of native birds.     

Simvastatin did not prevent nor restore ovariectomy-induced bone loss in adult rats

Current published results on whether statins have beneficial effects on bone metabolism have been conflicting so far. In order to further investigate if statins were promising candidates for the treatment for osteoporosis, we conducted a study in which rats were ovariectomized (OVX) at 6 months of age, allowed to lose bone for 60 days and followed by oral administration of simvastatin at the dose levels of 0.3-10 mg/kg/d for 60 days. PGE2 (6 mg/kg) was used as a positive control. Study endpoints included bone histomorphometry on the proximal tibial metaphysis (PTM) and the tibial diaphysis (TX), dual-energy X-ray absorptiometry on the right femur and micro computed tomography (ICT) on the 5th lumbar vertebra (LV). After 120 days of OVX, cancellous bone lost by 80% in the PTM and 18% in the LV accompanied by increased bone formation and resorption. Simvastatin at all dose levels did not affect bone volume, bone formation rate and bone erosion surface when compared to 120 day ovariectomized animals at all bone sites studied. By contrast, PGE2 restored cancellous and cortical bone area to sham control levels. In conclusion, this study demonstrated that unlike PGE2, oral administration of simvastatin did not have effects on cancellous or cortical bone formation and resorption; and consequently was not able to prevent further bone loss or restore bone mass in the osteopenic, OVX rats.     

Early Cambrian food webs on a trophic knife‐edge? A hypothesis and preliminary data from a modern stromatolite‐based ecosystem

Here we use the theory of ecological stoichiometry to propose and provide a preliminary test of a novel hypothesis that the Cambrian 'explosion' may have been triggered by changes in circulating P availability in the biosphere. We exposed living stromatolites from a spring-fed stream in Mexico to a gradient of P enrichment to examine subsequent effects on stromatolite C : P ratio and on the primary grazer, an endemic snail. Consistent with a previously hypothesized stoichiometric 'knife-edge', snail performance was maximal at intermediate P-enrichment, indicating in situ stoichiometric constraints because of high stromatolite C : P ratio along with high sensitivity to excessive P intake. These results are consistent with the idea that stoichiometric constraints may have delayed the evolutionary proliferation of animals in ancient stromatolite-dominated ecosystems and also suggest that high food P content can significantly impair consumers. We propose that ecosystem P availability may have impacted both the expansion and decline of animal taxa in the history of life.     

Adipose tissue inflammation and cancer cachexia: possible role of nuclear transcription factors

Cancer cachexia is a multifaceted syndrome whose aetiology is extremely complex and is directly related to poor patient prognosis and survival. Changes in lipid metabolism in cancer cachexia result in marked reduction of total fat mass, increased lipolysis, total oxidation of fatty acids, hyperlipidaemia, hypertriglyceridaemia, and hypercholesterolaemia. These changes are believed to be induced by inflammatory mediators, such as tumour necrosis factor-α (TNF-α) and other factors.Attention has recently been drawn to the current theory that cachexia is a chronic inflammatory state, mainly caused by the host’s reaction to the tumour. Changes in expression of numerous inflammatory mediators, notably in white adipose tissue (WAT), may trigger several changes in WAT homeostasis. The inhibition of adipocyte differentiation by PPARγ is paralleled by the appearance of smaller adipocytes, which may partially account for the inhibitory effect of PPARγ on inflammatory gene expression. Furthermore, inflammatory modulation and/or inhibition seems to be dependent on the IKK/NF-κB pathway, suggesting that a possible interaction between NF-κB and PPARγ is required to modulate WAT inflammation induced by cancer cachexia.In this article, current literature on the possible mechanisms of NF-κB and PPARγ regulation of WAT cells during cancer cachexia are discussed. This review aims to assess the role of a possible interaction between NF-κB and PPARγ in the setting of cancer cachexia as well as its significant role as a potential modulator of chronic inflammation that could be explored therapeutically.     

Sequence and structural analyses of nuclear export signals in the NESdb database

We compiled >200 nuclear export signal (NES)-containing CRM1 cargoes in a database named NESdb. We analyzed the sequences and three-dimensional structures of natural, experimentally identified NESs and of false-positive NESs that were generated from the database in order to identify properties that might distinguish the two groups of sequences. Analyses of amino acid frequencies, sequence logos, and agreement with existing NES consensus sequences revealed strong preferences for the Φ1-X(3)-Φ2-X(2)-Φ3-X-Φ4 pattern and for negatively charged amino acids in the nonhydrophobic positions of experimentally identified NESs but not of false positives. Strong preferences against certain hydrophobic amino acids in the hydrophobic positions were also revealed. These findings led to a new and more precise NES consensus. More important, three-dimensional structures are now available for 68 NESs within 56 different cargo proteins. Analyses of these structures showed that experimentally identified NESs are more likely than the false positives to adopt α-helical conformations that transition to loops at their C-termini and more likely to be surface accessible within their protein domains or be present in disordered or unobserved parts of the structures. Such distinguishing features for real NESs might be useful in future NES prediction efforts. Finally, we also tested CRM1-binding of 40 NESs that were found in the 56 structures. We found that 16 of the NES peptides did not bind CRM1, hence illustrating how NESs are easily misidentified.