Post-puff respiration measures on smokers of different tar yield cigarettes

The purpose of this study was to determine the effect of different tar yield cigarette brands on the post-puff inhalation/exhalation depth and duration for established smokers of the brands. The study was conducted with 74 established smokers of 1–17 mg Federal Trade Commission (FTC) tar products. The subjects were participating in a five-day inpatient clinical biomarker study during which time they were allowed to smoke their own brand of cigarette whenever they wished. On two separate days, the subjects' breathing pattern was measured using respiratory inductive plethysmography while they smoked one cigarette. This enabled the measurement of the post-puff inhalation volume, exhalation volume, inhalation duration, and exhalation duration for each subject after each puff on two of their own brand of cigarettes

Monitoring intermediate folding states of the td group I intron in vivo

Group I introns consist of two major structural domains, the P4-P6 and P3-P9 domains, which assemble through interactions with peripheral extensions to fold into an active ribozyme. To assess group I intron folding in vivo, we probed the structure of td wild-type and mutant introns using dimethyl sulfate. The results suggest that the majority of the intron population is in the native state in accordance with the current structural model, which was refined to include two novel tertiary contacts. The importance of the loop E motif in the P7.1-P7.2 extension in assisting ribozyme folding was deduced from modeling and mutational analyses. Destabilization of stem P6 results in a deficiency in tertiary structure formation in both major domains, while weakening of stem P7 only interferes with folding of the P3-P9 domain. The different impact of mutations on the tertiary structure suggests that they interfere with folding at different stages. These results provide a first insight into the structure of folding intermediates and suggest a putative order of events in a hierarchical folding pathway in vivo

First-instar monarch larval growth and survival on milkweeds in southern California: effects of latex, leaf hairs and cardenolides

Growth rate and survival of first-instar larvae of Danaus plexippus, a milkweed specialist, depended on milkweed species, and was related to the amount of latex produced from wounds, leaf cardenolide concentrations and the presence of leaf hairs. Larval growth was more rapid and survival was higher on leaves of Asclepias californica with experimentally reduced latex, and this species has characteristically high latex, low- to mid-range cardenolide concentrations, and very hirsute leaves. Similarly, growth was higher on reduced latex leaves of both A. eriocarpa (a high latex/high cardenolide, hirsute species) and A. erosa (glabrous fleshy leaves, high latex/high cardenolides). There were no differences in either survival or growth rate between larvae on reduced latex or control leaves of the low latex/low cardenolide A. fascicularis with soft glabrous leaves and both survival and growth rate were higher on this species than the other species tested. Larval growth rates on leaves with reduced latex were similar among ten milkweed species tested to date but differed from growth rates on intact leaves suggesting that latex and possibly included cardenolides are both important in first-instar monarch larval growth, development and survival. We show for a range of ecologically important milkweeds that experiments on cut plant material (no latex outflow) lead to higher growth rates compared to intact plants. Such laboratory assays based on detached leaves will be misleading if the objective is to determine the impact of treatments such as Bt-maize pollen on monarchs on field plants