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  • Connectionism  (1)
  • Glutathione  (1)
  • learning  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of nuclear medicine 23 (1996), S. 568-570 
    ISSN: 1619-7089
    Keywords: Technetium-99m sestamibi ; Multidrug resistance ; P-glycoprotein ; Glutathione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract An in vitro study was designed to evaluate the uptake of sestamibi (MIBI) in P-glycoprotein (Pgp) and glutathione-associated (GSH) multidrug-resistant (MDR) cell lines. MIBI uptake was studied in various human breast carcinoma cell lines, i.e. in wild-type (MCF7/wt) cells, in adriamycin-resistant (MCF7/adr) cells which express Pgp and in melphalan-resistant (MCF7/mph) cells with increased levels of GSH. The effects of buthiomine sulphoximine (BSO) and verapamil on MIBI uptake were also studied in the MCF7/mph and MCF7/adr cells respectively. The cells were incubated for 1 h with a dose of 0.1 MBq thallium-201 and technetium-99m MIBI. Both MIBI and201Tl uptakes were higher for MCF7/mph cells than for the other cells studied. The mean MIBI uptake in MCF7/adr cells was significantly lower than that in MCF7/wt cells (1.9%±0.5% vs 3.1%.0.6%;P 〈0.01). Verapamil treatment increased the MIBI uptake in MCF7/adr cells (to 2.6%.0.3%;P 〈0.05). Treatment of MCF7/mph cells with BSO resulted in a significant reduction in GSH content (from 243.2±81.1 nmoUmg protein to 17.6±4.4 nmol/mg protein;P 〈0.001). However, MIBI uptake in BSO-treated and untreated MCF7/mph cells was similar (4.43%±0.5% and 5.93%±1.7%, respectively;P 〉0.1). This study suggests that the uptake of MIBI is not diminished by glutathione-associated drug resistance and that MIBI uptake in a tumour sample does not necessarily indicate that a cancer is sensitive to drugs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Minds and machines 7 (1997), S. 1-37 
    ISSN: 1572-8641
    Keywords: Connectionism ; systematicity ; learning ; language ; semantics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Philosophy
    Notes: Abstract Fodor's and Pylyshyn's stand on systematicity in thought and language has been debated and criticized. Van Gelder and Niklasson, among others, have argued that Fodor and Pylyshyn offer no precise definition of systematicity. However, our concern here is with a learning based formulation of that concept. In particular, Hadley has proposed that a network exhibits strong semantic systematicity when, as a result of training, it can assign appropriate meaning representations to novel sentences (both simple and embedded) which contain words in syntactic positions they did not occupy during training. The experience of researchers indicates that strong systematicity in any form is difficult to achieve in connectionist systems. Herein we describe a network which displays strong semantic systematicity in response to Hebbian, connectionist training. During training, two-thirds of all nouns are presented only in a single syntactic position (either as grammatical subject or object). Yet, during testing, the network correctly interprets thousands of sentences containing those nouns in novel positions. In addition, the network generalizes to novel levels of embedding. Successful training requires a, corpus of about 1000 sentences, and network training is quite rapid. The architecture and learning algorithms are purely connectionist, but ‘classical’ insights are discernible in one respect, viz, that complex semantic representations spatially contain their semantic constituents. However, in other important respects, the architecture is distinctly non-classical.
    Type of Medium: Electronic Resource
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