State University of New York System

About: State University of New York System is a education organization based out in Albany, New York, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 54077 authors who have published 78070 publications receiving 2985160 citations.

The toxicokinetics and metabolism of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) and their relevance for toxicity.

Abstract: This article reviews the present state of the art regarding the toxicokinetics and metabolism of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). The absorption, body distribution, and metabolism can vary greatly between species and also may depend on the congener and dose. In biota, the 2,3,7,8-substituted PCDDs and PCDFs are almost exclusively retained in all tissue types, preferably liver and fat. This selective tissue retention and bioaccumulation are caused by a reduced rate of biotransformation and subsequent elimination of congeners with chlorine substitution at the 2,3,7, and 8 positions. 2,3,7,8-Substituted PCDDs and PCDFs also have the greatest toxic and biological activity and affinity for the cytosolic arylhydrocarbon (Ah)-receptor protein. The parent compound is the causal agent for Ah-receptor-mediated toxic and biological effects, with metabolism and subsequent elimination of 2,3,7,8- substituted congeners representing a detoxification process. Congener-specific affinity of PCDDs and PCDFs for the Ah-receptor, the genetic events following receptor binding, and toxicokinetics are factors that contribute to the relative in vivo potency of an individual PCDD or PCDF in a given species. Limited human data indicate that marked species differences exist in the toxicokinetics of these compounds. Thus, human risk assessment for PCDDs and PCDFs needs to consider species-, congener-, and dose-specific toxicokinetic data. In addition, exposure to complex mixtures, including PCBs, has the potential to alter the toxicokinetics of individual compounds. These alterations in toxicokinetics may be involved in some of the nonadditive toxic or biological effects that are observed after exposure to mixtures of PCDDs or PCDFs with PCBs.

Encoding social signals in the mouse main olfactory bulb.

Abstract: Mammalian urine releases complex mixtures of volatile compounds that are used in reproduction, territoriality and conspecific recognition. To understand how such complex mixtures are represented in the main olfactory bulb, we analysed the electrophysiological responses of individual mitral cells to volatile compounds in mouse urine. In both males and females, urine volatile compounds evoke robust responses in a small subset of mitral cells. Fractionation of the volatile compounds using gas chromatography showed that out of the hundreds of compounds present, mitral cells are activated by single compounds. One cohort of mitral cells responded exclusively to male urine; these neurons were activated by (methylthio)methanethiol, a potent, previously unknown semiochemical present only in male urine. When added to urine, synthetic (methylthio)methanethiol significantly enhances urine attractiveness to female mice. We conclude that mitral cells represent natural odorant stimuli by acting as selective feature detectors, and that their activation is largely independent of the presence of other components in the olfactory stimulus.

Designs for Collective Cognitive Responsibility in Knowledge-Building Communities

Abstract: This article reports a design experiment conducted over three successive school years, with the teacher's goal of having his Grade 4 students assume increasing levels of collective responsibility for advancing their knowledge of optics. Classroom practices conducive to sustained knowledge building were co-constructed by the teacher and students, with Knowledge Forum software supporting the production and refinement of the community's knowledge. Social network analysis and qualitative analyses were used to assess online participatory patterns and knowledge advances, focusing on indicators of collective cognitive responsibility. Data indicate increasingly effective procedures, mirrored in students' knowledge advances, corresponding to the following organizations: (a) Year 1—fixed small-groups; (b) Year 2—interacting small-groups with substantial cross-group knowledge sharing; and (c) Year 3—opportunistic collaboration, with small teams forming and disbanding under the volition of community members, based on...