Radiation therapy in the treatment of metastatic renal-cell carcinoma.
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Biomedical subjects
Publications and source records attributed to E Teissier.
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Radiotherapy still represents with surgery the cornerstone in the management of pediatric brain tumors. Techniques of irradiation have benefited greatly from modern imaging, CT scan and MRI for tumor-volume delineation, as well as megavoltage equipment, mainly linear accelerators delivering both high-energy X-Rays and electrons, widely used in cranial-spinal irradiations. Furthermore, new modalities of doses and volumes have been tested in various tumors (medulloblastomas, germ cell tumors...), in studies frequently combining chemotherapy with conventional therapies. Nevertheless, local control remains a major concern in tumors such as brain stem and high grade supratentorial gliomas. Concerning iatrogenic neurological sequelae, particularly harmful in children, limited data suggest an improvement in recent years. This improvement is partly due to the reduced prophylactic doses for the treatment of medulloblastomas, but further long-term observations are necessary. For these reasons, multiple technical innovations have been investigated. Some of them concern irradiation selectivity: stereotactic pencil beams, interstitial brachytherapy, heavy charged particles, 3-dimensional treatment planning. Others aim to increase the irradiation "efficacy": multifractionation, high LET particles, radiation-sensitizers.
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An attempt was made to correlate the physiological or the dimethylbenz(a)anthracene (DMBA)-enhanced serum prolactin (PRL) surge, which occurs in the afternoon of proestrus in female Sprague-Dawley (SD) rats, with physiological or pathological changes in two biochemical estimates of the tuberoinfundibular dopaminergic (TIDA) neuron activity. Dopamine (DA) and dihydroxyphenylacetic acid (DOPAC) concentrations as well as tyrosine hydroxylase (TH) activity were measured in the median eminence (ME) of control or DMBA-pretreated SD rats throughout the estrous cycle in relation to PRL secretion. In both groups of females, while the DA content was fairly constant, the DOPAC content and TH activity in the ME fluctuated markedly throughout the estrous cycle. Thus, in control animals, the DOPAC content, DOPAC/DA ratio and TH activity which were stable on the days of diestrus and morning of proestrus were markedly decreased at noon and early afternoon when serum PRL levels began to rise. Later in the afternoon of proestrus, when serum PRL levels were maximal, there was a marked but transient increase in the DOPAC content and DOPAC/DA ratio as well as a brief surge in TH activity. In the evening of the same day, when serum PRL returned to basal levels, the DOPAC content, DOPAC/DA ratio and TH activity were low. Finally on estrus morning, the DOPAC content, DOPAC/DA ratio and TH activity increased again to reach the diestrus levels. In DMBA-pretreated females, similar fluctuations in TIDA neuronal activity occurred during the estrous cycle, but the dynamics of these changes was altered: the DOPAC/DA ratio and TH activity first showed a marked increase in the morning of proestrus day, before decreasing dramatically.(ABSTRACT TRUNCATED AT 250 WORDS)
Our previous investigation presented evidence of interaction between alpha Ni3S2 and membranous and cellular lipids of lung cells, resulting in significant increases in linoleic, linolenic and arachidonic acids. The present work was designed to follow the metabolic fate of arachidonic acid in alpha Ni3S2-exposed guinea pig alveolar macrophages (GPAM) in culture (50 microM alpha Ni3S2 for 3 days). The metabolites of arachidonic acid were assessed by HPLC coupled with UV or electrochemical detection. The concentrations of malondialdehyde (MDA), hydroxyeicosatetraenoic acid (HETE), leukotrienes (LT) and reduced glutathione (GSH) were measured. In exposed cells a significant increase of MDA, a breakdown product of lipid peroxidation, was observed. In addition, the enzymatic reduction of 5-hydroperoxyeicosatetraenoic acid (5-HPETE) by the associated oxidation of GSH to GSSG increased 5-HETE in GPAM cells and decreased GSH. 5-Hydroperoxyeicosatetraenoic acid was furthermore converted to epoxides, such as leukotriene A4, and we also quantified in exposed cells a significant increase of its subsequent catabolites LTB4, LTC4 and LTE4. Direct measurements of MDA and other metabolites of arachidonic acid clearly show that exposure of GPAM cells to alpha Ni3S2 enhances lipid peroxidation. This lipid peroxidation is an autocatalytic free-radical process and could be responsible for DNA damage. Furthermore, alpha Ni3S2 intoxication induces the release of proinflammatory products, such as leukotrienes, and the decrease of glutathione.
Resistance to antineoplastic drugs has often been associated with P-glycoprotein overexpression, this certainly being not the sole mechanism. In order to characterize resistance to doxorubicin and cisplatin, we have analysed P-glycoprotein expression, topoisomerase II activity, glutathione and related enzymes in murine leukemic cells (doxorubicin or cisplatin-resistant). The doxorubicin-resistant cells contained P-glycoprotein, showed lower activities of glutathione S-transferase well as of glutathione reductase and topoisomerase II. The modifications observed in the most cisplatin-resistant cell line were a higher activity of glutathione S-transferase isoenzyme pi and topoisomerase II. These results suggest that drug uptake, glutathione metabolism as well as topoisomerase II activity are all characteristic of multidrug resistance.