Conditioned stimulus determinants of conditioned response form in Pavlovian fear conditioning.

Four experiments using barpress conditioned suppression in rats found that tone evoked more freezing (immobility) than did light. Still, tone and light appeared to have similar conditioned value as assessed by suppression in Experiments 1, 2, and 3, and by blocking, second-order conditioning, and overconditioning assays in Experiments 1, 2, and 3, respectively. Experiment 4 arranged for tone to evoke less suppression than light but more freezing. Results suggest that in fear conditioning, the nature of the conditioned stimulus affects the form of conditioned responding (strong vs. weak freezing). This conclusion extends one drawn by P. C. Holland (see record 1977-12147-001) on the basis of his work in appetitive conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Functional analysis of nodulin 26, an aquaporin in soybean root nodule symbiosomes

Upon infection of soybean roots, nitrogen-fixing bacteria become enclosed in a specific organelle known as the symbiosome. The symbiosome membrane (SM) is a selectively permeable barrier that controls metabolite flux between the plant cytosol and the symbiotic bacterium inside. Nodulin 26 (NOD 26), a member of the aquaporin (AQP) water channel family, is a major protein component of the SM. Expression of NOD 26 in Xenopus oocytes gave a mercury-sensitive increase in osmotic water permeability (Pf). To define the biophysical properties of NOD 26 water channels in their native membranes, symbiosomes were isolated from soybean root nodules and the SM separated as vesicles from the bacteria. Permeabilities were measured using stopped-flow fluorimetry in SM vesicles with entrapped carboxyfluorescein. Osmotic water permeability (Pf) of SM was high, with a value of 0.05 +/- 0.003 cm/s observed at 20 degrees C (mean +/- S.E.; n = 15). Water flow exhibited a low activation energy, was inhibited by HgCl2 (0.1 mM), and exhibited a unit conductance of 3.2 +/- 1.3 x 10(-15) cm3/s, a value 30-fold lower than that of AQP 1, the red blood cell water channel. Diffusive water permeability (Pd) was 0.0024 +/- 0.0002 cm/s, and the resulting Pf to Pd ratio was 18.3, indicating that water crosses the SM in single file fashion via the NOD 26 water channel. In addition to high water permeability, SM vesicles also show high mercury-sensitive permeability to glycerol and formamide, but not urea, suggesting that NOD 26 also fluxes these solutes. Overall, we conclude that NOD 26 acts as a water channel with a single channel conductance that is 30-fold lower than AQP 1. Because the solutes that permeate NOD 26 are far larger than water, and water appears to cross the channel via a single file pathway, solute flux across NOD 26 appears to occur by a pathway that is distinct from that for water.     

Observing bullying at school: The mental health implications of witness status.

This study explores the impact of bullying on the mental health of students who witness it. A representative sample of 2,002 students aged 12 to 16 years attending 14 schools in the United Kingdom were surveyed using a questionnaire that included measures of bullying at school, substance abuse, and mental health risk. The results suggest that observing bullying at school predicted risks to mental health over and above that predicted for those students who were directly involved in bullying behavior as either a perpetrator or a victim. Observing others was also found to predict higher risk irrespective of whether students were or were not victims themselves. The results are discussed with reference to past research on bystander and witness behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Progress and technology: their interdependency

This essay discusses the reciprocal relationship between progress and technology. It demonstrates that progress cannot be separated from technological improvements because improvements are believed to be the result of progress, and technological improvements cannot be conceived without progress because progress is believed to be the result of improvements. The idea of technological progress lies deep in the historical past, and can be found as early as the Greeks. Thinkers, such as Bacon, Descartes and Marx, who gave their support to the idea of progress in reference to technology, are analyzed, as are other significant factors, such as the cultural and historical importance of Christianity, which introduced both an eschatological interpretation of history and a linear conception of time. In conjunction with the ideas discussed above, technological progress is sustained by its own mythology, which extends and perpetuates the idea of progress indefinitely into the future.