Correlation between leukotriene D4-induced contraction and cytosolic calcium elevation: a quantitative and simultaneous evaluation in smooth muscle

The role of Ca++ as an intracellular messenger in leukotriene (LT)D4-induced muscle contraction was investigated by measuring force development and elevation in cytosolic Ca++ concentration simultaneously in strips of guinea pig ileal longitudinal muscle loaded with the fluorescent calcium indicator Fura 2. Upon addition of LTD4, a simultaneous increase in tension and cytosolic calcium concentration, [Ca++]i, was observed. Cumulative applications of LTD4 induced concentration-dependent increases in both muscle tension and [Ca++]i, being the half-maximal effect reached at approximately 6 to 9 nM. A statistically significant positive correlation (r = 0.993, P < .001) exists between the two parameters examined. Removal of calcium in the bathing solution, accompanied by addition of 7.5 mM EGTA, completely prevented any increase in either calcium levels or force development, thus indicating a role for Ca++ influx, rather than a release from intracellular stores. All of the LTD4 antagonists tested were able to counteract the effect of the leukotriene on both [Ca++]i and tension increase. However, although LY171883 shifted both of the LTD4 curves to the right in a parallel fashion, FPL 55712 and ICI 198,615 behaved as non-competitive antagonists in reversing the effect of LTD4 on [Ca++]i and tension. Thus, these results strongly suggest that changes in muscle tension induced by LTD4 are attributable to changes in cytosolic free Ca++ concentrations in guinea pig ileum.     

An adaptive overlay network inspired by social behaviour

Nature is a great source of inspiration for scientists, because natural systems seem to be able to find the best way to solve a given problem by using simple and robust mechanisms. Studying complex natural systems, scientists usually find that simple local dynamics lead to sophisticated macroscopic structures and behaviour. It seems that some kind of local interaction rules naturally allow the system to auto-organize itself as an efficient and robust structure, which can easily solve different tasks. Examples of such complex systems are social networks, where a small set of basic interaction rules leads to a relatively robust and efficient communication structure. In this paper, we present PROSA, a semantic peer-to-peer (P2P) overlay network inspired by social dynamics. The way queries are forwarded and links among peers are established in PROSA resemble the way people ask other people for collaboration, help or information. Behaving as a social network of peers, PROSA naturally evolves to a small world, where all peers can be reached in a fast and efficient way. The underlying algorithm used for query forwarding, based only on local choices, is both reliable and effective: peers sharing similar resources are eventually connected with each other, allowing queries to be successfully answered in a really small amount of time. The resulting emergent structure can guarantee fast responses and good query recall.     

Chemical deactivation of V2O5/WO3–TiO2 SCR catalysts by additives and impurities from fuels, lubrication oils and urea solution: Part II. Characterization study of the effect of alkali and alkaline earth metals

A characterization study on a practice-oriented V₂O₅/WO₃–TiO₂ SCR catalyst deactivated by Ca and K, respectively, was carried out using NH₃-TPD, DRIFT spectroscopy, and XPS as well as theoretical DFT calculations. It was found from NH₃-TPD experiments that strongly basic elements like K or Ca drastically affect the acidity of the catalysts. Detailed DRIFT spectroscopy experiments revealed that these poisoning agents mostly interact with the Brønsted acid sites of the V₂O₅ active phase, thus affecting the NH₃ adsorption. Moreover, these experiments also indicated that the V⁵⁺ = O sites are much less reactive on the poisoned catalysts. XPS investigations of the O 1s binding energies showed that the oxygen atoms of the V⁵⁺ = O sites are affected by the presence of the poisoning agents. Based on these results and on DFT calculations with model clusters of the vanadia surface, the poisoning mechanism is explained by the stabilization of the non atomic holes of the (0 1 0) V₂O₅ phase as a result of the deactivation element. Consequently, V–OH Brønsted acid sites and V⁵⁺ = O sites are inhibited, which are both of crucial importance in the SCR process. The deactivation model also gives an explanation to the very low concentrations of potassium needed to deactivate the SCR catalyst, since one metal atom sitting on such a non-atomic hole site deactivates up to four active vanadium centers.     

Hamiltonian-type Lyapunov functions

A flexible and systematic way for the construction of Lyapunov functions which lends itself to the use of nonlinear programming techniques is presented. The class of Lyapunov functions obtained is shown to be energy functions (Hamiltonians) for an equivalent system.     

AKT2, a member of the protein kinase B family, is activated by growth factors, v-Ha-ras, and v-src through phosphatidylinositol 3-kinase in human ovarian epithelial cancer cells

Three members have been identified in the protein kinase B (PKB) family, i.e., Akt/PKB alpha, AKT2/PKB beta, and AKT3/PKB gamma. Previous studies have demonstrated that only AKT2 is predominantly involved in human malignancies and has oncogenic activity. However, the mechanism of transforming activity of AKT2 is still not well understood. Here, we demonstrate the activation of AKT2 with several growth factors, including epidermal growth factor, insulin-like growth factor 1, insulin-like growth factor II, basic fibroblast growth factor, platelet-derived growth factor, and insulin, in human ovarian epithelial cancer cells. The kinase activity and the phosphorylation of AKT2 were induced by the growth factors and blocked by the phosphatidylinositol (PI) 3-kinase inhibitor, wortmannin, and dominant-negative Ras (N17Ras). Moreover, the activated Ras and v-Src, two proteins that transduce growth factor-generated signals, also activated AKT2, and this activation was not significantly enhanced by growth factor stimulation but was abrogated by wortmannin. These results indicate that AKT2 is a downstream target of PI 3-kinase and that Ras and Src function upstream of PI 3-kinase and mediate the activation of AKT2 by growth factors. The findings also provide further evidence that AKT2, in cooperation with Ras and Src, is important in the development of some human malignancies.     

Local recurrence of breast cancer after cytological evaluation of lumpectomy margins

Successful breast conservation therapy with optimal cosmesis requires adequate tumor excision and negative tumor margins. Therefore, more sensitive techniques are being developed to identify lumpectomy margins intraoperatively with greater accuracy. Unidentified microscopic disease is seemingly responsible for a local recurrence rate of up to 25 per cent 3 to 5 years after lumpectomy and radiotherapy for breast cancer patients. As a result, Moffitt Cancer Center has routinely used an intraoperative touch preparation cytology (TPC) protocol to evaluate the entire resected surface of all lumpectomies. In addition, resection margins were also evaluated by gross examination and by standard histology. In rare instances frozen sections were used to evaluate tumor margins. In this study 701 consecutive lumpectomy specimens were evaluated by TPC during the period of 9 years with a mean follow-up of 3.5 years. Local cancer recurrence was 2.7 per cent (mean recurrence, 2.53 years), in women whose lumpectomy margins were evaluated by TPC. Of interest, a local recurrence rate of 14.6 per cent was observed in patients who had referral lumpectomies evaluated by conventional histopathology. This study suggests that accurate margin assessment with TPC plays an important role in the control of local recurrence after breast conservation therapy. Therefore, we conclude the routine use of intraoperative TPC provides rapid, reliable, topographically accurate identification of residual microscopic disease at lumpectomy margins.     

Generalized Constructive Model of Hysteresis

We describe a generalized constructive model of rate independent scalar hysteresis. It consists of an algorithm that uses a set of experimental hysteresis minor loop vertical chords. The introduced model requires new, less constraining properties than the congruency and equal vertical chords properties required by the classical and the generalized Preisach models. Our model allows for fitting transition curves of order greater than two, despite its simple mathematical notation. Further, we describe interesting performance of the model in numerical evaluation and inversion     

Influence of a corpus luteum tissue extract on rabbit ovarian mesothelial cells

This study investigates rabbit ovarian mesothelial (OM) cells exposed in vitro to a crude corpus luteum extract (CLE; 60 micrograms/ml). The growth of OM cells was evaluated by measuring the change in cell number (mean % +/- standard error of mean, SEM), the number of cell population doublings (CPD +/- SEM), and the cell population doubling time in hours (CPDT +/- SEM) after 7.5 days of culture in a serum-poor medium. Quantitative estimates of surface morphology changes were obtained by analyzing the total number (mean no. +/- SEM), density (mean no./100 microns 2 +/- SEM), and length-to-diameter ratio (mean L/D +/- SEM) of microvilli. OM cells in control medium formed loosely cohesive monolayers, and grew 152.53 +/- 11.01% with a CPD of 0.59 +/- 0.08 and a CPDT of 117.29 +/- 6.43 hours. The exposed surface area of these cells was over 8,000 microns 2 and was covered in its epinuclear region by long and slender microvilli with a L/D of 6.01 +/- 0.29. The total number of microvilli in each control cell was 1977.52 +/- 120.49 with a density of 0.58 +/- 0.03/100 microns 2 in the epinuclear region and of 0.05 +/- 0.003/150 microns 2 in the remaining surface area (5,161.62 +/- 354.43 microns 2). In contrast, CLE-rich cells cultures grew 329.57 +/- 16.65%, with a CPD of 1.71 +/- 0.07 and a CPDT of 53.43 +/- 2.93 hours.(ABSTRACT TRUNCATED AT 250 WORDS)     

Myoepithelial-epithelial carcinoma of the parotid: cyto-histological description of a case

We report a case of epithelial-myoepithelial carcinoma of the parotid gland arised in a 72 years-old woman, in which the diagnosis was suspected on fine-needle aspiration and confirmed on surgical specimen. Immunohistochemical evidence for the dual differentiation (glandular and myoepithelial) of the tumour was obtained both on surgical specimen and cytological inclusion. Morphological features and proliferating index (MIB1) analysis suggest that this case is an intermediate grade malignant neoplasm. Main differential diagnosis of the epithelial-myoepithelial carcinoma with predominantly clear cell tumours of the salivary glands were discussed.