1,720,966 research outputs found
Mutagenicity of low-filtered 30 kVp X-rays, mammography X-rays and conventional X-rays in cultured mammalian cells
No full textPurpose. To measure the mutagenic effectiveness of low-filtered 30 kVp X-rays, mammography X-rays and conventional (200 kVp) X-rays in mammalian cells. Materials and methods Two different cell lines and mutation assays were used. Exponentially growing SV40-transformed human fibroblasts were exposed to graded doses of mammography (29 kVp, tungsten anode, 50 mum Rh filter) or conventional X-rays and the frequency of 6-thioguanine-resistent HPRT-deficient mutants was determined. Exponentially, growing hamster A(l) cells, which contain a single human chromosome 11 conferring the expression of the human surface protein CD59, were subjected to magnetic cell separation (MACS) in order to remove spontaneous mutants before irradiation with low-filtered 30 kVp (tungsten anode, 0.5 mm Al filter) or conventional X-rays. Fractions of radiation-induced CD59(-) mutants were quantified by flow-cytometry after immunofluorescence labelling of CD59 proteins Results: Mammography X-rays were more effective than conventional X-rays at inducing killing of human fibroblasts, whereas 30 kVp X-rays and conventional X-rays were about equally effective at killing A(1), cells. Mutant frequencies were linearly related to dose in both mutation assays. An RBE=2.7 was calculated for the yield of HPRT mutants in human fibroblasts exposed to mammography relative to conventional X-rays and an RBE=2.4 was obtained for the CD59 mutant frequency in A(L) cells irradiated with low-filtered 30 kVp relative to conventional X-rays. Conclusions: Both low-filtered 30 kVp and mammography X-rays are mutagenic in mammalian cells in vitro. It is unknown if and bow the enhanced mutagenicity mammography X-rays measured in human cells in vitro translates into breast cancer risk for predisposed women with an enhanced inherited risk for breast cancer. Although the ICRP guidelines attribute the same relative biological effectiveness to all radiations of low LET, including X- and y-radiations of all energies for radiobiological protection purposes including the assessment of risks in general terms, they also state that for the estimation of the likely consequences of an exposure of a known population, it will sometimes be better to use absorbed dose and specific data relating to the relative biological effectiveness of the radiations concerned and the probability coefficients relating to the exposed population' (ICRP 1991: 32). This latter statement may apply for the population of familial predisposed women. We hope that the presented data on the enhanced mutagenicity of mammography X-rays may stimulate a re-evaluation of the risk assessment of mammography for familial predisposed women. In the meantime, one should be cautious and avoid early and frequent mammography exposure of predisposed women. Alternative examination methods should be applied for these women with an inherited increased risk for breast cancer
A new anthracycline regimen for prolymphocytic leukemia? Study of a case report with flow cytometric implications.
No full textA case of prolymphocytic leukemia (PL) is reported, which showed a good response to a new antiblastic schedule (4-epidoxorubicin-asparaginase-dexamethasone) in spite of the resistance to other chemotherapy regimens. However during the course of the disease it was possible to observe the terminal appearance of a small aneuploid cell population in the peripheral blood of the patient and, in the same time, the clinical condition deteriorated considerably. The significance of this neoplastic progression and the pros and cons of aggressive chemotherapy regimens remain to be carefully evaluated in PL and related disorders.
PMID
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
In vitro proliferation and in vivo malignancy of cell lines simultaneously derived from a chemically-induced heterogeneous rat mammary tumor
No full textIdentification of clones in primary tumors responsible for proliferation, invasion, and metastasis was carried out. Four different aneuploid established cell lines derived from a ductal infiltrating mammary rat tumor induced by 7,12-dimethylbenz[a]anthracene were studied for proliferative and growth features in vitro and for tumorigenic and metastatic potential in vivo in nude mice. Clones, named RM1, RM2, RM3, and RM4, were characterized by different proliferative activity. Clone RM1 showed the highest proliferative activity by both tritiated thymidine incorporation and S-phase flow cytometry, followed by clone RM4. Conversely, clones RM2 and RM3 showed a lower proliferation rate. Growth-promoting activity, tested on 3T3 Swiss cells, was high in all clones, although RM1 showed significantly lower growth factors - releasing activity. Nude mice tumorigenesis demonstrated a strong tumor induction of line RM1 (100% of the mice after 47 ± 7 d) and a slightly lower tumor induction of line RM4 (70% of the mice after 69 ± 9 d). Line RM3 showed tumor induction in 40% of the mice after 186 ± 16 d. Lines RM2 showed no tumor induction. Metastasis occurred in mice treated with line RM1 only. Therefore, tumorigenesis and metastasis correlate with proliferation but not with the release of growth factors. In conclusion, flow cytometry monitoring of clones from heterogeneous primary tumors proved to be a suitable model for the study of in vivo malignancy and in vitro proliferation
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Static magnetic fields affect calcium fluxes and inhibit stress-induced apoptosis in human glioblastoma cells
No full textBackground: Epidemiologic data revealed increased brain tumor incidence in workers exposed to magnetic fields (MFs), raising concerns about the possible link between MF exposure and cancer. However, MFs seem to be neither mutagenic nor tumorigenic. The mechanism of their tumorigenic effect has not been elucidated. Methods: To evaluate the interference of MFs with physical (heat shock, HS) and chemical (etoposide, VP16) induced apoptoses, respectively, we exposed a human glioblastoma primary culture to 6 mT static MF. We investigated cytosolic Ca2+ ([Ca2+]i) fluxes and extent of apoptosis as key endpoints. The effect of MFs on HS- and VP16-induced apoptoses in primary glioblastoma cultures from four patients was also tested. Results: Static MFs increased the [Ca2+]i from a basal value of 124 ± 4 nM to 233 ± 43 nM (P < 0.05). MF exposure dramatically reduced the extent of HS- and VP16-induced apoptoses in all four glioblastoma primary cultures analyzed by 56% (range, 28-87%) and 44% (range, 38-48%), respectively. However, MF alone did not exert any apoptogenic activity. Differences were observed across the four cultures with regard to apoptotic induction by HS and VP16 and to MF apoptotic reduction, with an individual variability with regard to apoptotic sensitivity. Conclusion: The ability of static MFs to reduce the extent of damage-induced apoptosis in glioblastoma cells might allow the survival of damaged and possibly mutated cells. © 2002 Wiley-Liss, Inc
Increased number of cancer cells in bronchial washing fluid detected by combining conventional cytology and high-resolution flow cytometry
No full textDispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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