On the computation of nearly singular integrals in 3D BEM collocation

In this paper, we propose an efficient strategy to compute nearly singular integrals over planar triangles in R ³ arising in boundary element method collocation. The strategy is based on a proper use of various non‐linear transformations, which smooth or move away or quite eliminate all the singularities close to the domain of integration. We will deal with near singularities of the form 1/r, 1/r² and 1/r³, r=∥ x ? y ∥ being the distance between a fixed near observation point x and a generic point y of a triangular element. Extensive numerical tests and comparisons with some already existing methods show that the approach proposed here is highly efficient and competitive. Copyright © 2007 John Wiley & Sons, Ltd.     

Angiotensin-converting enzyme activity in stools of healthy subjects and patients with celiac disease

Angiotensin-converting enzyme (ACE) is a dipeptidylcarboxypeptidase that occurs in three types of cells: endothelial, epithelial, and neuroepithelial. ACE activity is present in plasma, urine, and vascular endothelium. High levels of ACE are found in the brush border of human small bowel. The aim of this study was to evaluate ACE activity in human stools and to find a correlation with the intestinal loss of epithelial cells. Fifteen healthy subjects (HS) (8 males, 7 females; age range 6-56 years), 20 patients with celiac disease (CD) (11 males, 9 females; age range 15-53 years), and 18 patients with CD in remission after a gluten-free diet (CD-GFD) (8 males, 10 females; age range 14-54 years) were enrolled in the study. The fecal ACE activity was measured in all groups. Fecal samples were kept at -20 degrees C for a subsequent test. In HS, fecal ACE activity was 21.03 +/- 16.17 nmol/min/100 g (mean +/- SD). In patients with CD with subtotal mucosa atrophy, ACE activity was significantly higher (113 +/- 88.94) than in HS and CD on GFD (36.65 +/- 23.9). We have demonstrated ACE activity in human stools. ACE activity in stools seems to derive from the microvilli of the intestinal mucosa, thus suggesting the potential usefulness of ACE determination as an index of enterocyte damage.     

Adrenomedullin, a new vasoactive peptide, is increased in preeclampsia

Adrenomedullin is a novel peptide that elicits a long-lasting vasorelaxant activity. Recently, we found high concentrations of adrenomedullin in maternal and umbilical cord plasma and in amniotic fluid in full-term human pregnancy, indicating a role of this peptide during gestation. To investigate the possibility that adrenomedullin is involved in the pathophysiology of preeclampsia, we measured its concentration in maternal and fetoplacental compartments. We studied 12 normotensive nonpregnant women, 13 hypertensive nonpregnant subjects, 29 patients with preeclampsia, and 30 normotensive pregnant women. In all patients, plasma was collected from the cubital vein, and amniotic fluid samples were obtained by transabdominal amniocentesis or at elective cesarean section. Plasma samples from umbilical vein and placental tissues were collected at delivery. Adrenomedullin was assayed on plasma and amniotic fluid samples using a specific radioimmunoassay, and its localization and distribution on placental sections was determined by immunohistochemistry. Adrenomedullin concentrations were higher in hypertensive than in normotensive nonpregnant patients. Pregnant women had higher adrenomedullin levels than nonpregnant subjects, although maternal plasma adrenomedullin concentrations did not differ between normal pregnant and preeclamptic women. Preeclamptic patients showed higher concentrations (P<0.01) than normotensive pregnant women of adrenomedullin in amniotic fluid (252+/-29 versus 112+/-10 fmol/ micromol creatinine) and umbilical vein plasma (18.1+/-2.1 versus 8. 5+/-1.1 fmol/mL). Increased local production of adrenomedullin is associated with preeclampsia. The fetus seems to be responsible for the higher levels of this hormone. Increased adrenomedullin concentrations may be necessary to maintain placental vascular resistance and/or fetal circulation at a physiological level.     

Electroosmotic flow through an $$\alpha$$-hemolysin nanopore

Nanopores are emerging as powerful tools for biosensing at a single molecule level, and their characterization under different working conditions is crucial for applications. In this perspective, we studied the ionic and electroosmotic flows across an \(\alpha\)-hemolysin nanopore using an extensive set of molecular dynamics simulations. Results show that the alteration in the solution pH has a dramatic effect on both electroosmotic flow and nanopore selectivity. Upon lowering the pH, the internal pore surface becomes globally more positively charged and, consequently, the transport of positive ions is hindered leading to a strong unbalance of positive and negative ionic fluxes. This unbalance gives rise to an intense electroosmotic flow that in certain regimes can overwhelm the ionic flux. Finally, we compared our data with continuum prediction for ideal electroosmotic flows, showing that, although the \(\alpha\)-hemolysin case is quite far from the ideality, the continuum theory is able to capture the magnitude of the electroosmotic mechanism.     

Systemically Induced Plant Volatiles Emitted at the Time of “Danger”

Feeding by Pieris brassicae caterpillars on the lower leaves of Brussels sprouts (Brassica oleracea var. gemmifera) plants triggers the release of volatiles from upper leaves. The volatiles are attractive for a natural antagonist of the herbivore, the parasitoid Cotesia glomerata. Parasitoids are attracted only if additional damage is inflicted on the systemically induced upper leaves and only after at least three days of herbivore feeding on the lower leaves. Upon termination of caterpillar feeding, the systemic signal is emitted for a maximum of one more day. Systemic induction did not occur at low levels of herbivore infestation. Systemically induced leaves emitted green leaf volatiles, cyclic monoterpenoids, and sesquiterpenes. GC-MS profiles of systemically induced and herbivore-infested leaves did not differ for most compounds, although herbivore infested plants did emit higher amounts of green leaf volatiles. Emission of systemically induced volatiles in Brussels sprouts might function as an induced defense that is activated only when needed, i.e., at the time of caterpillar attack. This way, plants may adopt a flexible management of inducible defensive resources to minimize costs of defense and to maximize fitness in response to unpredictable herbivore attack.     

Derivatives of benzimidazol-2-ylquinoline and benzimidazol-2-ylisoquinoline as selective A1 adenosine receptor antagonists with stimulant activity on human colon motility

A number of quinolines and isoquinolines connected in various ways to a substituted benzimidazol-2-yl system were synthesized and evaluated as novel antagonists of adenosine receptors (ARs) by competition experiments using human A(1), A(2A), and A(3) ARs. The new compounds were designed based on derivatives of 2-(benzimidazol-2-yl)quinoxaline, previously reported as potent and selective antagonists of A(1) and A(3) ARs. Among these, 3-[4-(ethylthio)-1H-benzimidazol-2-yl]isoquinoline 4b exhibited the best combination of potency toward the A(1) AR (K(i) =1.4 nM) and selectivity against the A(2A) (K(i) >10 μM), A(2B) (K(i)>10 μM), and A(3) ARs (K(i)>1 μM). Functional experiments in circular smooth muscle preparations of isolated human colon showed that 4b behaves as a potent and selective antagonist of the A(1) AR in the neuromuscular compartment of this intestinal region. Biological and pharmacological data suggest that 4b is a suitable starting point for the development of novel agents endowed with stimulant properties on colonic activity.     

Ambient PM exposure and DNA methylation in tumor suppressor genes: a cross-sectional study

Exposure to ambient air particles matter (PM) has been associated with increased risk of lung cancer. Aberrant tumor suppressor gene promoter methylation has emerged as a promising biomarker for cancers, including lung cancer. Whether exposure to PM is associated with peripheral blood leukocyte (PBL) DNA methylation in tumor suppressor genes has not been evaluated. In 63 male healthy steel workers with well-characterized exposure to metal-rich particles nearby Brescia, Italy, we evaluated whether exposure to PM and metal components was associated with PBL DNA methylation in 4 tumor suppressor genes (i.e., APC, p16, p53 and RASSF1A). Blood samples were obtained on the 1^st (baseline) and 4^th day (post-exposure) of the same work week and DNA methylation was measured using pyrosequencing. A linear mixed model was used to examine the correlations of the exposure with promoter methylation levels. Mean promoter DNA methylation levels of APC or p16 were significantly higher in post-exposure samples compared to that in baseline samples (p-values = 0.005 for APC, and p-value = 0.006 for p16). By contrast, the mean levels of p53 or RASSF1A promoter methylation was decreased in post-exposure samples compared to that in baseline samples (p-value = 0.015 for p53; and p-value < 0.001 for RASSF1A). In post-exposure samples, APC methylation was positively associated with PM₁₀ (β = 0.27, 95% CI: 0.13-0.40), and PM₁ (β = 0.23, 95% CI: 0.09-0.38). In summary, ambient PM exposure was associated with PBL DNA methylation levels of tumor suppressor genes of APC, p16, p53 and RASSF1A, suggesting that such methylation alterations may reflect processes related to PM-induced lung carcinogenesis.     

Engineering detonation nanodiamond - Polyaniline composites by electrochemical routes: Structural features and functional characterizations

Novel detonation nanodiamond (DND) - polyaniline (PANI) composite systems have been prepared by electrochemical polymerization techniques. Thanks to the use of two different electrochemical methods, i.e. cyclic voltammetry and chronoamperometry, it has been possible to emphasize the influence of DND particles on the nucleation mechanism of the conducting polymer. In particular, the presence of DND into the reaction environment has proven to modulate the organization of the aniline oligomers into π-stacked aggregates and to induce the production of one-dimensional nanostructures. Scanning and transmission electron microscopy was used to investigate the morphology of the final composites. The protonated conducting form of the PANI matrix has been evidenced by Raman spectroscopy and the ionic/electronic transport of the PANI-DND systems was tested by means of electrocatalysis measurements toward the iodine/iodide redox couple. Based on the present experimental data, the use of nanodiamond as filler for conducting polymer based nanocomposite represents not only a fascinating challenge for the production of advanced technological applications but it can also be exploited for the controlled growth of polymeric units and for the fabrication of tailored polymeric architectures.