University of Vermont

About: University of Vermont is a education organization based out in Burlington, Vermont, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 17592 authors who have published 38251 publications receiving 1609874 citations. The organization is also known as: UVM & University of Vermont and State Agricultural College.

Mechanism of water stress-induced xylem embolism.

Abstract: We investigated the hypothesis that water stress-induced xylem embolism is caused by air aspirated into functional vessels from neighboring embolized ones (e.g. embolized by physical damage) via pores in intervessel pit membranes. The following experiments with sugar maple (Acer saccharum Marsh.) support the hypothesis. (a) Most vessels in dehydrating stem segments embolized at xylem pressures 3 megapascals. This same pressure difference was found to be sufficient to force air across intervessel pits from air injection experiments of hydrated stem segments. This suggests air entry at pits is causing embolism in dehydrating stems. (b) Treatments that increased the permeability of intervessel pits to air injection also caused xylem to embolize at less negative xylem pressures. Permeability was increased either by perfusing stems with solutions of surface tension below that of water or by perfusion with a solution of oxalic acid and calcium. The mechanism of oxalic-calcium action on permeability is unknown, but may relate to the ability of oxalate to chelate calcium from the pectate fraction of the pit membrane. (c) Diameter of pores in pit membranes measured with the scanning electron microscope were within the range predicted by hypothesis (

Anxiolytics and antidepressants for smoking cessation.

Abstract: Background There are two reasons to believe antidepressants and anxiolytics might help in smoking. First, anxiety and depression are symptoms of nicotine withdrawal, and smoking cessation sometimes precipitates depression. Second, smoking appears to be due, in part, to deficits in dopamine, serotonin and norepinephrine, all of which are increased by anxiolytics and antidepressants. Objectives The aim of this review is to assess the effectiveness of such drugs in aiding long term smoking cessation. The drugs include bupropion; buspirone; diazepam; doxepin; fluoxetine; imipramine; meprobamate; moclobemide; nortriptyline; tryptophan; ondansetron; venlafaxine and the beta-blockers metoprolol, oxprenolol and propanolol. Search strategy We searched the Cochrane Tobacco Addiction Group trials register which includes trials indexed in Medline, Embase, SciSearch and PsycLit, and meetings abstracts. Selection criteria We considered randomized trials comparing anxiolytic or antidepressant drugs to placebo or an alternative therapeutic control for smoking cessation. We excluded trials with less than 6 months follow-up. Data collection and analysis We extracted data in duplicate on the type of study population, the nature of the drug therapy, the outcome measures, method of randomisation, and completeness of follow-up. The main outcome measure was abstinence from smoking after at least six months follow-up in patients smoking at baseline. We used the most rigorous definition of abstinence for each trial, and biochemically validated rates if available. Where appropriate, we performed meta-analysis using a fixed effects model. Main results There was one trial each of the anxiolytics diazepam, meprobamate, metoprolol and oxprenolol. There were two trials of the anxiolytic buspirone. None of these showed evidence of effectiveness in helping smokers to quit. There was one trial each of the antidepressants fluoxetine and moclobemide, two of nortriptyline, and four trials of bupropion. Nortriptyline and bupropion increased cessation and other antidepressants might also be effective. One trial found combined bupropion and nicotine patch produced higher quit rates than patch alone. Reviewer's conclusions There is little evidence that anxiolytics aid smoking cessation. Some antidepressants (bupropion and nortriptyline) can aid smoking cessation. It is not clear whether these effects are specific for individual drugs, or a class effect.