Four hexadentate salicylaldimine
ligands derived from bis(3-aminopropyl)ethylenediamine (BAPEN) that showed promise in previous rat experiments were selected for this study.
Methods: Following an evaluation of myocardial blood flow with [O-15]water PET, the pigs (total n=14) underwent a dynamic 90-min PET study with one of four Ga-68-labeled BAPEN derivatives (n=3-5 per tracer) either at rest or under adenosine stress. Serial arterial blood samples were collected during the imaging selleck chemicals llc for the measurements of total radioactivity, radiometabolites, plasma protein binding and blood-to-plasma ratio for the Ga-68 chelates. Time-activity curves of the left ventricular blood pool and myocardium were derived from PET images, and metabolite-corrected arterial input function was used for kinetic
modeling. Also, ex vivo biodistribution of Ga-68 radioactivity CX-6258 was analyzed.
Results: All four Ga-68 tracers showed undesirably slow myocardial accumulation over time, but their in vivo stability, clearance from blood and the kinetics of the myocardium uptake varied. [Ga-68][Ga-(sal)(2)BAPDM EM](I+) showed the highest myocardial uptake in PET images and tissue samples (myocardium-to-blood ratio 7.63+/-1.89, myocardium-to-lung ratio 3.03+/-0.33 and myocardium-to-liver ratio 1.80+/-0.82). However, there was no correlation between the myocardial perfusion measured with [O-15]water and the net uptake rates or K-1 values of the Ga-68 chelates.
Conclusion: Our results revealed that myocardial accumulation of the Ga-68 chelates proposed for myocardial perfusion imaging with PET was slow and not determined by myocardial perfusion in a large animal model. These findings suggest that the studied tracers are not suitable for clinical imaging of myocardial perfusion. (C) 2012 Elsevier Inc. All rights NU7026 reserved.”
“The authors present the context maintenance and retrieval (CMR) model of memory search, a generalized version of the temporal context model of M. W. Howard and M. J. Kahana (2002a), which
proposes that memory search is driven by,in internally maintained context representation composed of stimulus-related and source-related features. In the CMR model, organizational effects (the tendency for related items to cluster during the recall sequence) arise as a consequence of associations between active context elements and features of the studied material. Semantic clustering is due to longstanding context-to-item associations. whereas temporal clustering and source clustering are both due to associations formed during the study episode. A behavioral investigation of the three forms of organization provides data to constrain the CMR model, revealing interactions between the organizational factors. Finally, the authors discuss the implications of CMR for their understanding of a broad class of episodic memory phenomena and Suggest ways in which this theory may guide exploration of the neural correlates of memory search.