“Broken Promises: A History of Conscription in Canada Revised edition (Book Review)” by J.L. Granatstein and J.M. Hitsman

Review of Broken Promises: A History of Conscription in Canada (Revised Edition) by J.L. Granatstein and J.M. Hitsma

Review of “Crerar’s Lieutenants: Inventing the Canadian Junior Army Officer, 1939-45” by Geoffrey Hayes

Review of Crerar’s Lieutenants: Inventing the Canadian Junior Army Officer, 1939-45 by Geoffrey Haye

Extracellular NAD and ATP: Partners in immune cell modulation

Extracellular NAD and ATP exert multiple, partially overlapping effects on immune cells. Catabolism of both nucleotides by extracellular enzymes keeps extracellular concentrations low under steady-state conditions and generates metabolites that are themselves signal transducers. ATP and its metabolites signal through purinergic P2 and P1 receptors, whereas extracellular NAD exerts its effects by serving as a substrate for ADP-ribosyltransferases (ARTs) and NAD glycohydrolases/ADPR cyclases like CD38 and CD157. Both nucleotides activate the P2X7 purinoceptor, although by different mechanisms and with different characteristics. While ATP activates P2X7 directly as a soluble ligand, activation via NAD occurs by ART-dependent ADP-ribosylation of cell surface proteins, providing an immobilised ligand. P2X7 activation by either route leads to phosphatidylserine exposure, shedding of CD62L, and ultimately to cell death. Activation by ATP requires high micromolar concentrations of nucleotide and is readily reversible, whereas NAD-dependent stimulation begins at low micromolar concentrations and is more stable. Under conditions of cell stress or inflammation, ATP and NAD are released into the extracellular space from intracellular stores by lytic and non-lytic mechanisms, and may serve as ‘danger signals–to alert the immune response to tissue damage. Since ART expression is limited to naïve/resting T cells, P2X7-mediated NAD-induced cell death (NICD) specifically targets this cell population. In inflamed tissue, NICD may inhibit bystander activation of unprimed T cells, reducing the risk of autoimmunity. In draining lymph nodes, NICD may eliminate regulatory T cells or provide space for the preferential expansion of primed cells, and thus help to augment an immune response

Can an old alien benefit from rising ocean temperatures? An experimental and field study on the growth and local distribution of Codium fragile subsp. fragile (Chlorophyta)

Codium fragile subsp. fragile (hereafter C. fragile) is a widespread non-native chlorophyte. Experimental and observational approaches were used to examine the influence of temperature on its growth and local distribution in southwestern Norway, where it has been established for over 80 years. Growth was measured in laboratory experiments at current and predicted seasonal minimum and maximum seawater temperatures, and under natural conditions by recording length over 1 year in the field. The results indicated that if temperatures increase, C. fragile growth rate may increase in spring, but not in mid-autumn/winter due to low light. Thallus fragmentation was common in autumn/winter in the field, but very rare in the winter-temperature laboratory experiment, indicating that low temperature is not the only driver. Growth occurred at temperatures which are reported as too low for growth in other locations, suggesting that C. fragile can acclimatise/adapt to local temperature regimes. Local distribution was examined by surveying abundance using categories based on the number of thalli and their arrangement (scattered/patch/zone) at 46 stations from 2011 to 2016. Codium fragile colonised the stations relatively often, but was frequently lost from sites with only bedrock compared to sites with stony substratum present (cobbles/boulders). It was more likely to be consistently present at sites with stones and could form dominant patches of canopy in the upper sublittoral on this substratum. An increase in the number of stations with C. fragile present was seen after two mild winters, suggesting that higher minimum temperatures may increase site occupancy of C. fragile in this region