1,720,964 research outputs found
Effect of different platelet agonists on intracellular free Ca++ concentrations in human tumor cells: possible role in tumor growth
No full textModulation of cytoplasmic Ca++ concentration is a mechanism common to signal transduction pathways regulating many cellular phenomena, including the interactions of tumors with the hemostatic system. We have investigated the pro-aggregating and pro-coagulant activities of human tumor cell lines cultured in vitro and the ability of different platelet agonists to induce Ca++ transients in these cells. Cells of a malignant mesothelioma line activated platelets by a thrombin-dependent mechanism; on the contrary, HeLa cells, derived from a uterine cervical cancer, possessed ADP-dependent pro-aggregating activity, and DND-IA melanoma cells did not stimulate platelet aggregation. All cell lines showed a tissue-factor-like procoagulant property, more pronounced in mesothelioma cells. Furthermore, ADP was able to induce a transient increase in cytoplasmic Ca++ concentration in tumor cells from all lines; collagen showed this effect in mesothelioma cells and in HeLa cells, and thrombin was effective only in mesothelioma cells. PAF never induced Ca++ fluxes in any of the cell lines investigated. Finally, the calcium-channel blocker verapamil inhibited agonist-induced Ca++ transients in tumor cells and in vitro tumor-cell growth. These data may help to identify new possible mechanisms of the 2-way interaction of tumors with the hemostatic system
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Bombesin, calcium homeostasis and tumour growth
No full textBombesin and its analogues are a family of naturally occurring neuropeptides with potent mitogenic activity. The ability of this agent to induce Ca2+ transients is likely to be relevant in this context, but it is not yet clear whether the effect of bombesin on cell growth is directly and exclusively related to its capacity to increase cytoplasmic Ca2+ levels. The present study investigates the affect of bombesin on cytoplasmic Ca2+ concentrations in human tumour cells of different origin: lung adenocarcinoma, lung adenocarcinoma with properties of alveolar epithelial cells (A549 cell line), mesothelioma and uterine carcinoma (HeLa cell line). Furthermore, the ability of bombesin to promote the in vitro growth of the same cells has been analysed. This agent was able to induce a transient rise in cytoplasmic Ca2+ levels in tumour cells from all lines. In lung adenocarcinoma cells, but not in the other tumour cells, bombesin produced Ca2+ transients followed by a moderate but sustained elevation of Ca2+ levels. The effects of bombesin on tumour cell cytoplasmic Ca2+ levels were compared to those of other agents, i.e. adenosine diphosphate (ADP), collagen or thrombin, which have been reported to induce Ca2+ transients in tumour cells. Bombesin and ADP increased cytoplasmic Ca2+ levels in all cell lines, while collagen and thrombin gave rise to higher transients, but were effective only in some tumour cells and not in others. Furthermore, bombesin was able to stimulate in vitro growth of all the tumour cells, except for the A549 cells, in which this agent induced a slightly lower increase in cytoplasmic Ca2+ concentration. These data may aid a better understanding of the complex relationship between the Ca2+ mobilizing and mitogenic activities of bombesin and may be of general interest when considering the biological effects of growth-stimulating factors
In vitro effect of bombesin-related peptides on the procoagulant activity of alveolar macrophages
No full textBombesin-related peptides (BRP) are present in the lung during foetal life and are mitogenic for normal bronchial epithelial cells, pulmonary fibroblasts, and small-cell lung carcinoma cell lines. Increased levels of BRP have been described in the adult lung of cigarette smokers and in smoking related lung diseases. BRP have also been involved in the network of neuroimmune interactions, having been shown to modulate the phagocytic function of monocytes and alveolar macrophages. BRP have recently been shown to modulate the release of procoagulant activity (PCA) by human monocytes and alveolar macrophages after a 24 h culture. The aim of this study was to evaluate the effect of bombesin on cell-associated PCA of alveolar macrophages (AMs) obtained from asymptomatic subjects. In basal conditions, AMs were found to possess a low procoagulant activity, that was not affected by their preincubation (4 h at 37 degrees C) with phorbol myristate acetate (1 microgram-mL-1). On the contrary, endotoxin (lipopolysaccharide (LPS)) induced a significant increase of procoagulant activity of macrophages when used at a concentration of 1 microgram.mL-1, in the same experimental conditions; whilst a lower (1 ng.mL-1) concentration of LPS nonsignificantly enhanced cell-associated PCA. Treatment of AMs with synthetic bombesin (BN) alone (10(-6) to 10(-10) M) did not enhance cell-associated PCA, whilst a significant effect was seen when BN was added to the lower concentration of LPS (BN 10(-6) M+LPS 1 ng.mL-1: 12.6 U.10(-6) cells; LPS alone 1 ng.mL-1: 7.8 U.10(-6) cells)
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Bombesin, calcium homeostasis and tumour growth
No full textBombesin and its analogues are a family of naturally occurring neuropeptides with potent mitogenic activity. The ability of this agent to induce Ca2+ transients is likely to be relevant in this context, but it is not yet clear whether the effect of bombesin on cell growth is directly and exclusively related to its capacity to increase cytoplasmic Ca2+ levels. The present study investigates the affect of bombesin on cytoplasmic Ca2+ concentrations in human tumour cells of different origin: lung adenocarcinoma, lung adenocarcinoma with properties of alveolar epithelial cells (A549 cell line), mesothelioma and uterine carcinoma (HeLa cell line). Furthermore, the ability of bombesin to promote the in vitro growth of the same cells has been analysed. This agent was able to induce a transient rise in cytoplasmic Ca2+ levels in tumour cells from all lines. In lung adenocarcinoma cells, but not in the other tumour cells, bombesin produced Ca2+ transients followed by a moderate but sustained elevation of Ca2+ levels. The effects of bombesin on tumour cell cytoplasmic Ca2+ levels were compared to those of other agents, i.e. adenosine diphosphate (ADP), collagen or thrombin, which have been reported to induce Ca2+ transients in tumour cells. Bombesin and ADP increased cytoplasmic Ca2+ levels in all cell lines, while collagen and thrombin gave rise to higher transients, but were effective only in some tumour cells and not in others. Furthermore, bombesin was able to stimulate in vitro growth of all the tumour cells, except for the A549 cells, in which this agent induced a slightly lower increase in cytoplasmic Ca2+ concentration. These data may aid a better understanding of the complex relationship between the Ca2+ mobilizing and mitogenic activities of bombesin and may be of general interest when considering the biological effects of growth-stimulating factors
Effect of interferon alpha, interferon gamma and tumor necrosis factor on the procoagulant activity of human cancer cells
No full textBACKGROUND: It is not known whether the different cytokines may influence the procoagulant activity of cancer cells; the purpose of this study was to investigate the effect of interferon alpha, interferon gamma and tumor necrosis factor on the procoagulation capacity of human cancer cells cultured "in vitro" or isolated from tumor tissues.
METHODS: "In vitro" cultured tumor cell lines were derived from a patient with malignant mesothelioma and a patient with lung adenocarcinoma. Cells isolated from 6 carcinomas of different origin were also investigated. The procoagulant activity of the cells before and after treatment with the cytokines was expressed as RBT U/10(5) cells or RVV U/10(5) cells.
RESULTS: Short-term incubation of tumor cells cultured "in vitro" with cytokines did not modify their procoagulant activity; after longer incubation however, interferon alpha induced a significant increase in the procoagulant activity of mesothelioma cells, while interferon gamma induced and increase in the procoagulant activity of lung adenocarcinoma cells. Furthermore, short-term incubation of cells isolated from tumor tissues with interferon gamma or tumor necrosis factor resulted in a significant increase of procoagulant activity, while interferon alpha had no effect.
CONCLUSIONS: Altogether, these data demonstrate that the cytokines may influence the expression of the different procoagulant activities of tumor cells
Verapamil inhibits to different extents agonist-induced Ca2+ transients in human tumor cells and in vitro tumor cell growth
No full textPlatelet agonists are known to contribute to the regulation of cytoplasmic Ca2+ levels in tumor cells and this property could be relevant in the stimulation of cell proliferation. In the present study we investigated the ability of ADP, collagen and thrombin to increase cytoplasmic Ca2+ levels in different human tumor cell lines (mesothelioma, DND-1A melanoma, HeLa uterine carcinoma) and we analyzed the effect of the calcium channel blocker verapamil on Ca2+ fluxes and on in vitro tumor cell growth. ADP was able to induce a transient increase in the cytoplasmic Ca2+ concentration in tumor cells from all lines; collagen showed this effect in mesothelioma cells and in HeLa cells, and thrombin was effective only in mesothelioma cells. Verapamil inhibited Ca2+ fluxes induced by the effective agonists in a dose-dependent manner. Values of IC50 for inhibition of ADP-induced Ca2+ transients were 63.5 microM in mesothelioma cells, 97.3 microM in DND-1A cells and 93.5 microM in HeLa cells, while those for inhibition of collagen-induced Ca2+ movements were slightly higher (170.2 microM in mesothelioma cells and 112.3 microM in HeLa cells) and the value of IC50 for inhibition of thrombin-induced Ca2+ fluxes (evaluated only in mesothelioma cells) was lower (22.5 microM). The drug dose-dependently also inhibited the in vitro growth of tumor cells; values of IC50 for growth inhibition were 21.8 microM in mesothelioma cells, 9.1 microM in DND-1A cells and 6.4 microM in HeLa cells, suggesting that the antiproliferative activity of verapamil was partly Ca(2+)-independent. These data may be of interest to elucidate the mechanisms of the two-way interactions of tumors with the hemostatic system and may help to identify new pharmacologic strategies for their control
- …
