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  • 1
    Electronic Resource
    Electronic Resource
    Successful and unsuccessful approaches to imaging carcinoids: Comparison of a radiolabelled tryptophan hydroxylase inhibitor with a tracer of biogenic amine uptake and storage, and a somatostatin analogue (1996)
    Springer
    European journal of nuclear medicine 23 (1996), S. 131-140 
    Details
    ISSN: 1619-7089
    Keywords: Carcinoid ; Radionuclide imaging ; Phenylalanine ; Metaiodobenzylguanidine ; Pentetreotide ; Iodophenylalanine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A mouse mastocytoma model was used to determine the biodistribution and tumour uptake of four radiopharmaceuticals developed to target the serotonin synthetic pathway in carcinoid tumours. Three of the compounds were competitive inhibitors of the rate-limiting enzyme of serotonin synthesis, tryptophan hydroxylase. Radiolabelled iodo-dl-phenylalanine (iodine-131 PIPA) was found to have the highest uptake and tumourto-liver ratio. Four patients with known carcinoid tumours were then injected with 0.5 mCi131I-PIPA and imaged at 1, 4, 24 and 48 h post-injection. The radiopharmaceutical, however, failed to localize in the known tumour sites. This result was in contrast to the authors' experience of131I- and123I-MIBG imaging of carcinoid tumours. Seven patients with known metastatic carcinoid tumours, two patients with symptoms of recurrence following tumour resection, one patient with completely resected disease, and two patients with a flushing syndrome of uncertain aetiology were studied with131I-MIBG. Three of the seven patients with known metastatic disease had positive131I-MIBG scans. Both patients with clinical evidence of recurrent disease had negative scans, as did the patient who was considered to have had complete resection of her primary tumour. The two patients with idiopathic flushing syndrome also had negative scans. Among seven patients imaged with123I-MIBG there were four true-negative scans and one falsenegative, the latter in a patient with biochemical and CT evidence of recurrence. In a seventh patient with distant metastases there was variable uptake in some of the lesions. Four patients were studied with indium-111 penetetreodide. Two patients with metastatic carcinoid disease had positive scans, although hepatic metastases were not seen in one. Another two with idiopathic flushing syndrome had normal studies. The literature suggests that up 50% of carcinoid tumour cases are detected with131I-MIBG, compared to a sensitivity of 87% reported with somatostatin receptor imaging using111In-pentetreotide. The experience with123I-MIBG is much less extensive. The mechanisms of carcinoid tumour localization for each of the three classes of radiotracers are discussed and contrasted to their varying sensitivities. The relative success of131I-MIBG and111In-pentetreotide relative to131I-PIPA may be related to the fact that131I-MIBG is actively taken up and stored by the enterochromaffin cells of the tumours and111In-pentetreotide binds to cell surface receptors, whereas131I-PIPA binds to tryptophan hydroxylase, which may be present in quantities too small to permit tumours to be imaged.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01731835
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  • 2
    Electronic Resource
    Electronic Resource
    Plasticized single conductung polyelectrolytes based on poly (AMPS) (1996)
    Springer
    Ionics 2 (1996), S. 53-62 
    Details
    ISSN: 1862-0760
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Poly(2-acrylamido-2-methyl-propane-1-sulphonic acid), poly(AMPS), has been ion exchanged with lithium and sodium to form alkali metal ion conducting polyelectrolytes. In the pure form these materials are rigid and would thus show limited conductivity. However addition of water or dimethylsulphoxide, as plasticizers, increases the conductivity by several orders or magnitude. The thermal analysis and NMR relaxation studies of these systems suggest that the increase in conductivity is as a direct result of increased ion mobility although the FTIR evidence still suggests significant ion association consistent with weak electrolytes. Although the Tg's of the sodium form of the polymer were higher, this system displayed higher conductivities than lithium which can be explained by a greater degree of ion dissociation and hence a larger number of charge carriers in the case of sodium poly(AMPS).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02375869
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  • 3
    Electronic Resource
    Electronic Resource
    Ion conductive poly(ethylene oxide-dimethyl siloxane) copolymers (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 3465-3470 
    Details
    ISSN: 0887-624X
    Keywords: poly(ethylene oxide-dimethyl siloxane) copolymers ; ionic conductive polymers ; polymer electrolyte ; ionic conductivity ; dimethyl dimethoxy/diethoxysilane ; polyethylene glycol ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of poly(ethylene oxide-dimethyl siloxane) copolymers,  -  [SiMe2O(CH2CH2O)n]m  -  (n = 2, 3, 4, 5, 6.4, 8.7, 13.3), were synthesised by the reaction of polyethylene glycol with dimethyl dimethoxy/diethoxysilane. Corresponding ion-conductive polymers were prepared by complexing these copolymers with salts (sodium tetrafluoroborate or ammonium adipate). The highest conductivity of these systems at room temperature was 3 × 10-4 S cm-1 and 6 × 10-5 S cm-1, respectively. The glass transition temperature of these copolymers is reported and is seen to be dependent on the length of the ether units. The effects of siloxane content, salt concentration, and temperature on the conductivity are discussed. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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