Moments of Moments and Branching Random Walks.

We calculate, for a branching random walk X n ( l ) to a leaf l at depth n on a binary tree, the positive integer moments of the random variable 1 2 n ∑ l = 1 2 n e 2 ß X n ( l ) , for ß ∈ R . We obtain explicit formulae for the first few moments for finite n. In the limit n → ∞ , our expression coincides with recent conjectures and results concerning the moments of moments of characteristic polynomials of random unitary matrices, supporting the idea that these two problems, which both fall into the class of logarithmically correlated Gaussian random fields, are related to each other.

Isolation and partial characterization of an opioid-like 88 kDa hibernation-related protein.

Previous studies show that infusion of hibernating woodchuck albumin (HWA) induces hibernation in summer-active ground squirrels and results in profound behavioral and physiological depression in primates. These effects are reversed by the administration of opiate antagonists, suggesting that the putative hibernation induction trigger (HIT) may act through opioid receptors. We have demonstrated that both HIT-containing plasma and the synthetic alpha opioid D-Ala2-D-Leu5-enkephalin (DADLE), which mimics the activity of HIT in hibernators, extend tissue survival time of a multi-organ autoperfusion system by 3-fold. In this study we present the first data showing biological activity with a much more highly purified plasma fraction from hibernating woodchucks, identified as the hibernation-related factor (HRF). Both the HRF and DADLE show opiate-like contractile inhibition in the mouse vas deferens (Mvd) bioassay. We also have preliminary evidence in an isolated rabbit heart preparation indicating that the HRF and DADLE act similarly to restore left ventricular function following global myocardial ischemia. Furthermore, we have partially sequenced an alpha 1-glycoprotein-like 88 kDa hibernation-related protein (p88 HRP) present in this fraction, which may prove to be the blood-borne HIT molecule.

Hibernation-induction trigger. I. Opioid-like effects of prairie dog plasma albumin on induced contractility of guinea pig ileum.

Studies have shown that plasma albumin fractions (PAFs) from hibernating mammals can inhibit induced contractility of the guinea pig ileum similarly to morphine. This study examined PAFs from two species of prairie dogs, one that undergoes natural seasonal hibernation (white-tailed, WT) and one that does not but can be induced to hibernate (black-tailed, BT). Dose-response curves of lyophilized PAF yielded IC50 values (mg) of 20.23 for summer WT, 15.53 for hibernating WT, 15.45 for summer BT, and 13.16 for winter-active BT. Winter samples from both species have IC50s lower than samples from summer animals, indicating greater potency of winter PAFs in suppressing guinea pig ileum contractility and therefore the presence of more opioid ligands in winter prairie dog plasma. Studies to elucidate receptor selectivity of PAF continue.

Reactivation of silenced, virally transduced genes by inhibitors of histone deacetylase.

Retroviral and adeno-associated viral sequences can dramatically silence transgene expression in mice. We now report that this repression also occurs in stably infected HeLa cells when the cells are grown without selection. Expression of a transduced lacZ gene (rAAV/CMVlacZ) is silenced in greater than 90% of cells after 60 days in culture. Surprisingly, high-level expression can be reactivated by treating the cells with sodium butyrate or trichostatin A but not with 5-azacytidine. When cell clones with integrated copies of rAAV/CMVlacZ were isolated, lacZ expression was silenced in 80% of the clones; however, lacZ expression was reactivated in all of the silenced clones by treatment with butyrate or trichostatin A. The two drugs also reactivated a silenced globin gene construct (rAAV/HS2alphabetaAS3) in stably infected K562 cells. Trichostatin A is a specific inhibitor of histone deacetylase; therefore, we propose that hyperacetylation of histones after drug treatment changes the structure of chromatin on integrated viral sequences and relieves repression of transduced genes. The reactivation of silenced, transduced genes has implications for gene therapy. Efficient viral gene transfer followed by drug treatment to relieve suppression may provide a powerful combination for treatment of various genetic and infectious diseases.

Circannual variations in bear plasma albumin and its opioid-like effects on guinea pig ileum.

Previous studies suggest that hibernation is controlled by an opioid system. In this study we examined the effect of plasma albumin fractions drawn from black bears at timed intervals while in hibernation or during the awake state in fall and winter, on induced contractility of the guinea pig ileum. Four hundred nM morphine produced typical suppression of contractility and 400 or 1000 nM naloxone (an opiate antagonist) restored it. Twenty mg of lyophilized albumin fraction from the winter hibernating bear caused similar suppression, the effect being greater than that of either summer bear or winter-active bear plasma albumin. Naloxone reversed the suppression in all cases. Strong suppression of contractility was also demonstrated with 2.5 nM [D-Pen2.5]-enkephalin (DPDPE), a delta agonist, but only minor suppression with 2.5 nM dynorphin A, a kappa agonist. Results support the opioid nature of the albumin-bound hibernation-induction trigger substance, that it binds to the delta opiate receptor, and that delta agonist opioid production may increase during the hibernation season.