The positive regulation of cell proliferation by a calcium-cyclic AMP control couplet

Hepatocyte proliferation is positively regulated by calcium/cyclic AMP in vivo and in vitro

Involvement of cAMP and cAMP-dependent protein kinase in the initiation of DNA synthesis by rat liver cells.

Addition of calcium to calcium-deprived cultures of T51B rat liver cells caused brief bursts of cAMP production and cAMP-dependent protein kinase activity which were followed almost immediately by a stimulation of DNA synthesis. PKInh, a specific polypeptide inhibitor of the catalytic subunits of cAMP-dependent protein kinases, inhibited the DNA-synthetic response to calcium addition without stopping the preceding cAMP surge. Addition of cAMP to the calciumdeprived cultures increased protein kinase activity and stimulated DNA synthesis, both of which were inhibited by PKInh. DNA synthesis in these cultures was not stimulated by adding type I cAMP-dependent protein kinase holoenzyme to the calcium-deficient medium, but it was stimulated by type II cAMP-dependent protein kinase holoenzyme or the catalytic subunit from either type I or type II holoenzyme. The stimulatory actions of the type II holoenzyme or the catalytic subunits were inhibited by PKInh. Thus, a burst of cAMP-dependent protein kinase activity was ultimately responsible for the stimulation of DNA synthesis in calcium-deprived T51B cells by calcium or cAMP and it might also be involved in the events leading to initiation of DNA synthesis in many, if not all, normally cycling cells

Interannual similarity and variation in seasonal circulation of Mars' atmospheric Ar as seen by the Gamma Ray Spectrometer on Mars Odyssey

International audienceMore than 3 Mars' years (MY) of atmospheric argon (Ar) measurements are used to study annual and seasonal variations in atmospheric transport and mixing. Data are obtained over the period 20 May 2002 to 4 May 2008 by the Gamma Subsystem (GS) of the Gamma Ray Spectrometer (GRS) on the Mars Odyssey spacecraft in orbit around Mars. Here we augment previous studies of Mars' Ar in which strong seasonal variations were observed and horizontal meridional mixing coefficients for the southern hemisphere were computed. Comparison of year-to-year seasonal abundance shows strong similarity but also some short-period (~15-30 L s) and interannual variations. Evidence for short periods of strong eddy transport is exhibited during autumn and winter. The seasonal change in Ar concentration for southern latitudes is relatively gradual and well defined, but seasonal changes at high northern latitudes are chaotic and indicate that atmospheric disturbance is ubiquitous. Major topographic landforms (Elysium, Tharsis, Noachis Terra, Hellas) apparently have little control over seasonal Ar concentration at the spatial resolution of the GRS data set. Some indication of local enhanced Ar concentration is present from 30N to 60N for the Hellas and Tharsis sectors in late winter and early spring. The data show some significant (3) differences between MY 26 and MY 27 in geographical sectors that are likely produced by local weather. The GS data do not show seasonal variation of Ar at equatorial and low-latitude zones, in contrast to those from the Alpha Particle X-ray Spectrometer (APXS) measurements from the Mars Exploration Rovers. Copyright 2012 by the American Geophysical Union

Control of the initiation of chromosome replication by Ca 2+ , Ca 2+ -calmodulin and cAMP: An overview

NRC publication: Ye

Using concept-based instruction in the L2 classroom: Perspectives from current and future language teachers

A number of recent studies (see, for example, Lantolf, 2010; Negueruela & Lantolf, 2006; van Compernolle, 2011) have focused on the use of learning tools developed according to the principles of concept-based instruction (CBI). Using videorecorded data from interviews and observations of classroom instruction, our study seeks to contribute to the CBI research by examining the implementation of this framework from the perspectives of pre-service and novice teachers of French and Spanish. Therefore, the overarching goal of this study is to understand how and to what extent teachers embrace or reject a pedagogical approach that does not necessarily align with a textbook’s explanation of a grammar point. We have chosen to focus on the teaching of verbal aspect since textbooks for learners of both French and Spanish typically present rules of thumb for learning past tense use without explaining the systematic concept of verbal aspect. The case studies presented in this article demonstrate that – in some instances and for a variety of reasons – experienced, novice, and pre-service teachers prefer materials, techniques, and approaches that are more familiar, albeit not as potentially beneficial for learners