1,721,056 research outputs found
Determination of Pt in biological samples by inductively coupled plasma atomic emission spectrometry (ICP-AES) with electrothermal vaporization (ETV).
No full textAn electrothermal sample vaporization device was combined with an inductively coupled plasma spectrometer for the determination of Pt in biological samples (serum, urine, tissues). A commercial graphite furnace for atomic absorption was connected to an ICP torch using an electrically heated quartz tube. The argon gas stream was slightly modified. Sample aliquots up to 100 microL were dried at 120 degrees C, ashed at 1400 degrees C and subsequently heated to 2700 degrees C. The aerosol obtained was transported into a 2.2 kW argon ICP by means of a carrier gas flowing at 1.4 L/min. The detection limit was found to be 0.25-0.5 micrograms/L, depending upon the matrix. These values are one order of magnitude better than those obtained using conventional nebulizers. The precision (RSD) at 50 micrograms/L ranged from 0.04 to 0.07 and the accuracy (evaluated as recovery) was 103.2% to 105.3%. Because the matrix effects could not be neglected, different calibration curves were prepared for each kind of medium. The analytical capabilities of the method described were found to be suitable for the determination of Pt used in routine monitoring during chemotherapy with Cisplatin and other Pt-based compounds
Increased sensitivity to the Platelet-Derived Growth Factor (PDGF) Receptor inhibitor STI571 in chemoresistant high-grade glioma cells is associated with enhanced PDGF-BB-mediated signaling and STI571-induced Akt inactivation
No full textThe platelet-derived growth factor receptor (PDGFR) is a tyrosine kinase, implicated in the development and progression of different tumors, including gliomas. Chemoresistance is a common feature of malignant gliomas. Since receptor tyrosine kinases contribute to chemoresistance in tumors, we addressed whether PDGFR signaling might confer selective growth advantage to chemoresistant cells. The effects of the PDGFR inhibitor STI571 on proliferation and PDGFR signaling were compared in chemosensitive and cisplatin-selected, chemoresistant sublines derived from glioma and from two other PDGFR-expressing tumors (ovarian carcinoma and neuroblastoma). The chemoresistant glioma U87/Pt cells were twofold more sensitive to STI571 growth-inhibitory effects than the chemosensitive U87 cells, and two- to threefold more sensitive than five unrelated glioma cell lines. The other two paired cell lines were equally responsive. Sensitization of U87/Pt cells correlated with upregulation of the PDGF-B isoform and with PDGF-BB-induced Akt overactivation, which was prevented by STI571. STI571 specifically inhibited PDGF-BB-, but not PDGF-AA- or stem cell factor-mediated signaling. In serum-containing medium, STI571 decreased phospho-Akt in U87/Pt cells, but not in U87, while activating extracellular signal-regulated kinase (Erk) in both. STI571 antiproliferative effects were partially reverted by constitutively active Akt. Cotreatment with inhibitors of phosphatidylinositol 3'-kinase (PI3K) or mitogen-activated protein kinase kinase (MEK) resulted in enhanced growth inhibition in glioma cells. Our results suggest that increased PDGF-BB signaling may sensitize chemoresistant glioma cells to STI571, suggesting a therapeutic potential for STI571 in patients with malignant gliomas refractory to chemotherapy. Simultaneous blockade of PDGFR and PI3K or Erk pathway may enhance therapeutic targeting in glioma
Multidrug resistance gene transcript level, and P-glycoprotein expression in paediatric malignant mesenchymal tumours.
No full textAbstract: Twenty-four malignant mesenchymal tumor specimens were analysed for. human multidrug resistance (MDRI) gene transcript levels using Northern and slot blot techniques. The presence of P-glycoprotein was assessed in 12 of the 24 samples by immunohistochemistry using the monoclonal antibody (MAb) C219. Ina eased MDRI transcript levels were found in 2 (8.3%), while, using immunohistochemistry, 2 samples were positive and 3 faintly positive (41.6%). Over-all, elevated P-glycoprotein ol MDRI transcript levels were found in tumours of 6 patients, 3 of whom ale dead. The relationship to MDRI expression and subsequent resistance to chemotherapy has to be established
A pilot study of high-dose carboplatin and pulsed etoposide in the treatment of childhood solid tumors.
No full textCarboplatin was administered at 1,000 mg/m2/course in combination with etoposide at 300 mg/m2/course to 23 patients aged 5 months to 16 years. Five patients were affected by neuroblastoma, four by CNS tumors, three by Ewing's sarcoma, two by rhabdomyosarcoma, two by malignant teratoma, two by Wilms' tumor, two by head and neck carcinoma, one by hepatoblastoma, one by synovial sarcoma, and one by Langerhans-cell histiocytosis. Eleven patients were pretreated, seven of them with high-dose cisplatin. The overall response rate was 7/11 (64%) for pretreated and 10/12 (83%) for previously untreated patients. Myelosuppression was the main side effect, with anemia and thrombocytopenia more pronounced than leukopenia. Gastrointestinal toxicity and ototoxicity were very mild; nephrotoxicity and neurotoxicity other than hearing loss were not observed. In children with malignant tumors, the therapeutic activity of carboplatin at high doses, even in combination chemotherapy, deserves further studies
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
Synergistic post-transcriptional regulation of the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) by miR-101 and miR-494 specific binding.
No full textmicroRNAs (miRNAs) are a class of regulatory small non-coding molecules that control gene expression at post-transcriptional level. Deregulation of miRNA functions affects a variety of biological processes also involved in the etiology of several human mendelian and complex diseases. Recently, aberrant miRNA expression has been observed in Cystic Fibrosis (CF), an autosomal-recessive genetic disorder caused by mutations in the CFTR gene, in which a genotype-phenotype correlation is not always found. In order to determine miRNA role in CFTR post-transcriptional regulation, we searched for miR-responsive elements in the CFTR 3'-UTR. In silico analysis, performed using different computational on-line programs, identified some putative miRNAs. Both miR-101 and miR-494 synthetic mimics significantly inhibited the expression of a reporter construct containing the 3'-UTR of CFTR in luciferase assays. Interestingly, miR-101/miR-494 combination was able to markedly suppress CFTR activity by approximately 80% (p<0.001). This is one of the first in vitro studies implicating microRNAs as negative regulators of the CFTR gene expression. miRNA aberrant expression and function might explain the wide phenotypic variability observed among CF patients
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