No abstract

We examine the expiration of the IPO quiet period, which occurs after the 25th calendar day following the offering.

Alzheimer's disease (AD) is widely held to be a disorder associated with oxidative stress due, in part, to the membrane action of amyloid~3-peptide (A/3). A~-associated free radicals cause lipid peroxidation, a major product of which is 4-hydroxy-2-trans-nonenal (HNE). We determined whether HNE would alter the conformation of synaptosomal membrane proteins, which might be related to the known neurotoxicity of A~3and HNE. Electron paramagnetic resonance spectroscopy, using a protein-specific spin label, MAL-6 (2,2 ,6,6-tetramethyl-4-maleimidopiperidin-1-oxyl), was used to probe conformational changes in gerbil cortical synaptosomal membrane proteins, and a lipid-specific stearic acid label, 5-nitroxide stearate, was used to probe for HNE-induced alterations in the fluidity of the bilayer domain of these membranes. Synaptosomal membranes, incubated with low concentrations of HNE, exhibited changes in protein conformation and bilayer order and motion (fluidity). The changes in protein conformation were found to be concentration-and time-dependent. Significant protein conformational changes were observed at physiologically relevant concentrations of 1-10 p~MHNE, reminiscent of similar changes in synaptosomal membrane proteins from senile plaque-and A/3-rich AD hippocampal and inferior parietal brain regions. HNE-induced modifications in the physical state of gerbil synaptosomal membrane proteins were prevented completely by using excess glutathione ethyl ester, known to protect neurons from HNEcaused neurotoxicity. Membrane fluidity was found to increase at higher concentrations of HNE (50 /2M). The results obtained are discussed with relevance to the hypothesis of A/3-induced free radical-mediated lipid peroxidation, leading to subsequent HNE-induced alterations in the structure and function of key membrane proteins with consequent neurotoxicity in AD brain.

Most initial public offerings (IPOs) feature "lockup" agreements, which bar insiders from selling the stock for a set period following the IPO, usually 180 days. We examine stock price behavior in the period surrounding lockup expiration for a sample of 2,529 firms from 1988 to 1997. We find that lockup expirations are, on average, associated with significant and negative abnormal returns, but the losses are concentrated in firms with venture capital backing. For the venture-capital-backed group, the largest losses occur for high-tech firms and firms with the greatest post-IPO stock price increases, the largest relative trading volume in the period surrounding expiration, and the highest quality underwriters.

Duffie (1996) examines the theoretical impact of repo “specials” on the prices of Treasury securities and concludes that, all else the same, an issue on special will carry a higher price than an otherwise identical issue. We examine this hypothesis and find strong evidence in support of it. We also examine whether the liquidity premium associated with “on‐the‐run” issues is due to repo specialness and find evidence of a distinct effect. Finally, we investigate whether auction tightness and percentage awarded to dealers are related to subsequent specialness and find that both variables àre generally significant.