Electrochemical Postpolymerization Modification and Deconstruction of Macromolecules.

Electrolysis is an emerging approach to polymer postpolymerization modification, deconstruction, and depolymerization. Electrochemical reactions are particularly appealing for macromolecular transformations because of their high selectivity, ability to be externally monitored, and intrinsic scalability. Despite these desirable features and the recent resurgent use of small-molecule electrochemical reactions, the development of macromolecular electrolysis has been limited.

Access to Functionalized Materials by Metal-Free Ring-Opening Metathesis Polymerization of Active Esters and Divergent Postpolymerization Modification.

Metal-free ring-opening metathesis polymerization (MF-ROMP) is an emerging polymerization strategy that provides access to ROMP materials by using organic initiators and photoredox catalysts. Unlike metal-mediated ROMP, MF-ROMP is not highly tolerant toward functionalized monomers. Herein, we report that pentafluorophenyl esters are polymerizable under MF-ROMP conditions to produce homopolymers, statistical copolymers, and block copolymers.

C-H Functionalization and Allylic Amination for Post-Polymerization Modification of Polynorbornenes.

Post-polymerization modification (PPM) via direct C-H functionalization is a powerful synthetic strategy to convert polymer feed-stocks into value-added products. We found that a metal-free, Se-catalyzed allylic C-H amination provided an efficient method for PPM of polynorbornenes (PNBs) produced via ring-opening metathesis polymerization. Inherent to the mechanism of the allylic amination, PPM on PNBs preserved the alkene functional groups along the polymer backbone, while also avoiding transposition of the double bonds.

An Ion-Pairing Approach to Stereoselective Metal-Free Ring-Opening Metathesis Polymerization.

Stereochemistry can have a profound impact on polymer and materials properties. Unfortunately, straightforward methods for realizing high levels of stereocontrolled polymerizations are often challenging to achieve. In a departure from traditional metal-mediated ring-opening metathesis polymerization (ROMP), we discovered a remarkably simple method for controlling alkene stereochemistry in photoredox mediated metal-free ROMP.

Virtually justifiable homicide: the effects of prosocial contexts on the link between violent video games, aggression, and prosocial and hostile cognition.

Previous work has shown that playing violent video games can stimulate aggression toward others. The current research has identified a potential exception. Participants who played a violent game in which the violence had an explicitly prosocial motive (i.

Terror management theory and self-esteem revisited: the roles of implicit and explicit self-esteem in mortality salience effects.

Three studies tested the roles of implicit and/or explicit self-esteem in reactions to mortality salience. In Study 1, writing about death versus a control topic increased worldview defense among participants low in implicit self-esteem but not among those high in implicit self-esteem. In Study 2, a manipulation to boost implicit self-esteem reduced the effect of mortality salience on worldview defense.

It's the thought that counts: The role of hostile cognition in shaping aggressive responses to social exclusion.

Prior research has confirmed a casual path between social rejection and aggression, but there has been no clear explanation of why social rejection causes aggression. A series of experiments tested the hypothesis that social exclusion increases the inclination to perceive neutral information as hostile, which has implications for aggression. Compared to accepted and control participants, socially excluded participants were more likely to rate aggressive and ambiguous words as similar (Experiment 1a), to complete word fragments with aggressive words (Experiment 1b), and to rate the ambiguous actions of another person as hostile (Experiments 2-4).

Behavioral and biochemical studies in rats following prenatal treatment with beta-adrenoceptor antagonists.

Increased motor activity and poor performance in the active avoidance test were observed in the offspring of rats treated with dl-propranolol or sotalol during pregnancy, but not with atenolol and d-propranolol. All substances were administered in drinking water from days 8-22 of gestation. A significant increase in the density of muscarinic acetylcholine receptors in the hippocampus was found for dl-propranolol and sotalol, at 35 and 20 days of age, respectively.

Different behavioral deficits are induced by anoxia/hypoxia in neonatal and senescent rats: blockade by MK-801.

Rats exposed on their first postnatal day to 100% nitrogen for 25 min developed hyperactivity and lower performance in passive avoidance task during development. Administration of MK-801 (0.5 mg/kg i.

Central catecholaminergic dysfunction and behavioural disorders following hypoxia in adult rats.

Wistar male rats, 3-4 months old, were made to breathe for 6 h a sub-lethal hypoxic atmosphere consisting of 8% oxygen and 92% nitrogen. Following this treatment, these rats were subjected to a series of behavioral and biochemical tests starting 30 days and ending at about 180 days after the hypoxic insult. an age-matched control group was subjected to the same series of tests.

Tacrine or arecoline mediates reversal of anoxia- or AF64A-induced behavioural disorders in the developing rat.

A 25 min anoxia, or an intracerebroventricular bilateral 2 nmol dose of ethylcholine aziridinium (AF-64A), administered postnatally to male rat pups, elicited on further development of these behavioural disorders, which are partly related to central cholinergic hypofunction. These included a hyperkinetic syndrome and inferior performance in the passive avoidance test. The anoxia-lesioned group but not the AF-64-A-lesioned one, showed an inferior performance in the active avoidance test.

Myocardial response to alpha-agonist (phenylephrine) in relation to age.

We studied the inotropic effect of the alpha-agonist phenylephrine on human and rat myocardium in relation to age. Strips of human atrial myocardium, discarded during cardiac surgery, were obtained from pediatric (2 to 18 months) and adult (40 to 60 yr) patients, and their electrically driven contractions were studied. The inotropic response of pediatric myocardium to phenylephrine was five times larger than that of the adult myocardium (p less than .

Benzene-derived free radical--a possible mediator of its carcinogenicity. I. Ultrastructural and functional studies on the effect of benzene on human white blood cells and its possible prevention.

The assumption that benzene exerts its leukemogenic action on cell components after being converted to a transient and relatively stable free radical is supported by the in vitro effect of benzene on the ultrastructure of human peripheral blood polymorphonuclear (PMN) cells, lymphocytes and monocytes. The effect was examined with a transmission and scanning electron microscope and was found to affect both the internal and external architecture of PMN cells and monocytes in a dose-dependent manner. No effect was observed on lymphocytes.

Enhanced electroretinogram in cats induced by exposure to mercury acetate.

The present study was undertaken in order to verify whether, and how, retinal functions are affected by subacute poisoning with organic mercury. Mercury acetate in various concentrations (0.025-0.

Behavioral differences in the developing rat following postnatal anoxia or postnatally injected AF-64A, a cholinergic neurotoxin.

Rat pups were submitted postnatally to one of two procedures: a 25-min exposure to 100% nitrogen or an i.c.v.

A novel cardiotoxic polypeptide from the venom of Atractaspis engaddensis (burrowing asp): cardiac effects in mice and isolated rat and human heart preparations.

A new cardiotoxic polypeptide isolated from the venom of the snake Atractaspis engaddensis has an LD50 of 15 micrograms/kg body weight in white mice. Intravenous administration in mice of lethal doses of the toxin causes, within seconds, marked changes in the ECG, consisting primarily of a transient slope elevation of the S-T segment, a temporary diminution of the S-wave and an increase in the amplitudes of the R- and T-waves. Concomitantly, and apparently unrelated to these changes, a severe A-V block develops and leads to complete cardiac arrest within a few min.

Nonopiate effect of naloxone on cardiac muscle contractility.

To test the hypothesis that naloxone exerts a direct positive inotropic effect on the cardiac muscle, we employed two in vitro models. In one set of experiments we demonstrated that injection of 1 mg naloxone into an isolated perfused rat heart produced a significant increase in the amplitude of contraction. In another set of experiments we exposed an isolated and spontaneously contracting rat right atrium in a tissue bath to naloxone, and demonstrated that the amplitude of contraction increased significantly within a few minutes of naloxone administration.

Positive inotropic response to alpha-adrenergic stimulation in an electrically driven rat left atrium: the role of extracellular calcium.

We studied the positive inotropic response induced by alpha-adrenergic receptor stimulation in an electrically driven rat left atrium. alpha-Adrenergic stimulation resulted in a prolonged positive inotropic response that reached its maximum within 5-7 min. The kinetics of the onset of the positive inotropic response were different for pure alpha-adrenergic, pure beta-adrenergic, and mixed adrenergic stimulation.

Split immunosuppression of contact cell-mediated and of IgE hypersensitivity responses to dinitrofluorobenzene in mice.

Contact sensitivity (CS), anti-DNP (dinitrophenyl) IgG and IgE type antibodies were induced by skin applications of the contact sensitizer dinitrofluorobenzene. CS response was suppressed by treatment with the monovalent hapten dinitrobenzene sulfonate (DNBS) but was not affected by treatment with the DNP-conjugates (DNP22-Ficoll, DNP17-polyethylene glycol and DNP2-polyvinylpyrrolidone). On the other hand, IgE type response was depressed by treatment with the various DNP conjugates but was not affected by DNBS.

Phenytoin pharmacokinetics in catamenial epilepsy.

It is not known why the frequency of seizures sometimes increases in the perimenstrual period (catamenial epilepsy). We have examined the possibility that changes in anticonvulsant pharmacokinetics may be responsible. Seventeen women with seizures who were taking phenytoin (DPH) and whose seizures were more frequent perimenstrually were examined twice each, once on the first or second menstrual day and again after 2 weeks.

Hyperactivity in rats following postnatal anoxia.

A model of hyperactive rats was produced by exposing pups to severe anoxia within 24 h following birth. These rats demonstrated augmented motor activity in ambulation, sniffing and rearing activities in an open field. Activity was significantly increased at 10 days of age, maximal at 20-25 days and returned to normal values around 6 weeks of age.