Concordia University

About: Concordia University is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Context (language use) & Control theory. The organization has 13565 authors who have published 31084 publications receiving 783525 citations. The organization is also known as: Sir George Williams University & Loyola College, Montreal.

The Role of Corticotropin-Releasing Factor and Corticosterone in Stress- and Cocaine-Induced Relapse to Cocaine Seeking in Rats

Abstract: We have shown previously that footshock stress and priming injections of cocaine reinstate cocaine seeking in rats after prolonged drug-free periods (Erb et al., 1996). Here we examined the role of brain corticotropin-releasing factor (CRF) and the adrenal hormone corticosterone in stress- and cocaine-induced reinstatement of cocaine seeking in rats. The ability of footshock stress and priming injections of cocaine to induce relapse to cocaine seeking was studied after intracerebroventricular infusions of the CRF receptor antagonist D-Phe CRF12-41, after adrenalectomy, and after adrenalectomy with corticosterone replacement. Rats were allowed to self-administer cocaine (1.0 mg/kg/infusion, i.v) for 3 hr daily for 10-14 d and were then placed on an extinction schedule during which saline was substituted for cocaine. Tests for reinstatement were given after intermittent footshock (10 min; 0.5 mA) and after priming injections of saline and cocaine (20 mg/kg, i.p.). Footshock reinstated cocaine seeking in both intact animals and animals with corticosterone replacement but not in adrenalectomized animals. The CRF receptor antagonist D-Phe CRF12-41 blocked footshock-induced reinstatement at all doses tested in both intact animals and animals with corticosterone replacement. Reinstatement by priming injections of cocaine was only minimally attenuated by adrenalectomy and by pretreatment with D-Phe CRF12-41. These data suggest that brain CRF plays a critical role in stress-induced, but only a modulatory role in cocaine-induced, reinstatement of cocaine seeking. Furthermore, the data show that although reinstatement of cocaine seeking by footshock stress requires minimal, basal, levels of corticosterone, stress-induced increases in corticosterone do not play a role in this effect.

Toeholds, Bid Jumps, and Expected Payoffs in Takeovers

Abstract: We estimate sequentially outcome-probabilities and expected payoffs associated with first-, second- and final bids in a large sample of tender offer contests. Rival bids arrive quickly and produce large bid-jumps. Greater bidder toeholds (pre-bid ownership of target shares) reduce the probability of competition and target resistance and are associated with both lower bid-premiums and lower pre-bid target stock-price runups. The expected payoff to target shareholders is increasing in the bid-premium and in the probability of competition, but decreasing in the bidder's toehold. The initial bidder's expected payoff is significantly positive in the "rival-bidder-win" outcome, in part reflecting gains from the pending toehold-sale. Despite these dramatic toehold effects, only half of the initial bidders acquire toeholds.

Network Culture: Politics for the Information Age

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Mining WordNet for a Fuzzy Sentiment: Sentiment Tag Extraction from WordNet Glosses

Abstract: Many of the tasks required for semantic tagging of phrases and texts rely on a list of words annotated with some semantic features. We present a method for extracting sentiment-bearing adjectives from WordNet using the Sentiment Tag Extraction Program (STEP). We did 58 STEP runs on unique non-intersecting seed lists drawn from manually annotated list of positive and negative adjectives and evaluated the results against other manually annotated lists. The 58 runs were then collapsed into a single set of 7, 813 unique words. For each word we computed a Net Overlap Score by subtracting the total number of runs assigning this word a negative sentiment from the total of the runs that consider it positive. We demonstrate that Net Overlap Score can be used as a measure of the words degree of membership in the fuzzy category of sentiment: the core adjectives, which had the highest Net Overlap scores, were identified most accurately both by STEP and by human annotators, while the words on the periphery of the category had the lowest scores and were associated with low rates of inter-annotator agreement.