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Patrick J O'Donnell

Publications and source records attributed to Patrick J O'Donnell.

5 recordsLinked to original sources
PubMed2006

Eye movements and lexical ambiguity resolution: investigating the subordinate-bias effect.

Recent debates on lexical ambiguity resolution have centered on the subordinate-bias effect, in which reading time is longer on a biased ambiguous word in a subordinate-biasing context than on a control word. The nature of the control word--namely, whether it matched the frequency of the ambiguous word's overall word form or its contextually instantiated word meaning (a higher or lower frequency word, respectively)--was examined. In addition, contexts that were singularly supportive of the ambiguous word's subordinate meaning were used. Eye movements were recorded as participants read contextually biasing passages that contained an ambiguous word target or a word-form or word-meaning control. A comparison of fixation times on the 2 control words revealed a significant effect of word frequency. Fixation times on the ambiguous word generally fell between those on the 2 controls and were significantly different than both. Results are discussed in relation to the reordered access model, in which both meaning frequency and prior context affect access procedures.

Adolescent↗
PubMed2004

Development of bladder urothelial hyperplasia and carcinoma in portacaval shunted rats is not dependent upon urolithiasis.

The pathogenesis of bladder tumors is poorly understood, possibly due to the lack of a suitable experimental model that is drug-free. The aim of the present study was to determine whether bladder tumors could be reproduced reliably in portacaval anastomosis (PCS) rats and whether induction is due to urolithiasis from the development of bladder stones. Eighteen male Sprague-Dawley rats were anaesthetised with isoflurane. Twelve were subjected to portacaval anastomosis and allowed to recover for 38 weeks and the remaining 6 underwent sham control procedures. They were then re-anaesthetised, the anastomosis checked for patency and the bladders and livers excised, fixed, block-mounted, sectioned and stained with haematoxylin and eosin staining for histological examination. None of the control rats developed bladder wall abnormalities of any recognisable nature. However, 5 (42%) of the PCS group had urothelial lesions and bladder stones present and a further 5 (42%) had urothelial lesions alone with no recognisable evidence of bladder stone formation. One PCS rat had bladder stones alone and the remaining PCS rat had an apparently normal bladder epithelium and no stones. Thus, 10 (83%) of the 12 PCS rats developed epithelial lesions and half of these did not display evidence of bladder stone formation. This represented a highly significant difference between the development of bladder stones and the occurrence of urothelial lesions in PCS rats (P > 1.0, chi(2) analysis). Urothelial lesions, therefore, can be reproduced in PCS rats. Their occurrence appears independent of bladder stone formation.

Animals↗
PubMed2003

Peptidylglycine-alpha-amidating monooxygenase and pro-atrial natriuretic peptide constitute the major membrane-associated proteins of rat atrial secretory granules.

Peptidylglycine-alpha-amidating monooxygenase (PAM) is a bi-functional enzyme known to catalyze the post-translational bioactivation of signaling peptides. Although PAM is highly concentrated within the cardiac atrium, this tissue does not produce appreciable amounts of alpha-amidated peptides and thus, the function of PAM in atrium remains largely unknown. In this study, we demonstrate that PAM co-localizes in atrial secretory granules with the storage form of atrial natriuretic peptide (pro-ANP, amino acids 1-126), a hormone involved in the maintenance of blood pressure and fluid homeostasis. ANP is not amidated by PAM, but rather is processed to its active form (amino acids 99-126) by the proteolytic cleavage of pro-ANP. We demonstrate here by subcellular fractionation and biochemical analyses that PAM co-localizes with pro-ANP in secretory granules, where together they constitute the two most abundant membrane-associated proteins, accounting for approximately 95% of the total granular membrane protein. Respectively, light and electron microscopic immunohistochemistry show intense staining for PAM in atrial cardiomyocyctes and subcellular localization of PAM to secretory granules. Additionally, we demonstrate that while pro-ANP is readily found in the soluble contents of the granule lumen, significant amounts remain tightly associated with the membranes even after vigorous washing and estimate the molar ratio of pro-ANP to PAM to be approximately 30:1 in the membrane fraction. We postulate here that the primary function of PAM in the atrium is structural rather than enzymatic. In this regard, PAM may contribute to the packaging of pro-ANP within the secretory granule and possibly function in the presentation of pro-ANP for proteolytic processing.

Animals↗
PubMed2003

Context effects in word recognition: evidence for early interactive processing.

This study investigated whether a prior context influenced lexical access as indexed by participants' electrophysiological response in the N1 from 132 to 192 ms poststimulus. Ambiguous, high-frequency (HF), and low-frequency (LF) words were presented in neutral and biasing contexts. Event-related potentials (ERPs) for ambiguous words were compared with those for unambiguous HF (word form) and LF (word meaning) control words. Word frequency effects in the N1 extended previous ERP findings. A marginal effect of context for LF words provided electrophysiological support for the context-by-frequency interaction shown in reaction time paradigms. In neutral context, responses to ambiguous words were comparable to responses to HF words, and in biasing context (where context instantiated the subordinate sense), responses to ambiguous words were comparable to responses to LF words. The results establish temporal parameters for the early operation of context in lexical access. These constraints are more consistent with an interactive than a modular account.

Adolescent↗