Repetitive spreading depression induces nestin protein expression in the cortex of rats and mice. Is this upregulation initiated by N-methyl-D-aspartate receptors?

NoIn the November issue (2001) of Neuroscience Letters, Holmin et al. (Neurosci. Lett. 314 (2001) 151) reported that the synthesis of the intermediate filament protein nestin was upregulated by potassium-induced depolarization in the rat cortex. In this letter, we provide supplementary evidence that repeated cortical spreading depression elicited by potassium induces a delayed upregulation of nestin. However, we argue against the authors' conclusion, Nestin expression was N-methyl-D-aspartate (NMDA)-receptor dependent since dizocilpine (MK-801) treatment abolished the response because spreading depression itself is very sensitive to NMDA-receptor block, and the drug treatment was initiated prior to potassium application to the cortex in Holmin et al.'s study

Genetic diversity maintained among fragmented populations of a tree undergoing range contraction

Dwarf birch (Betula nana) has a widespread boreal distribution but has declined significantly in Britain where populations are now highly fragmented. We analysed the genetic diversity of these fragmented populations using markers that differ in mutation rate: conventional microsatellites markers (PCR-SSRs), RADseq generated transition and transversion SNPs (RAD-SNPs), and microsatellite markers mined from RADseq reads (RAD-SSRs). We estimated the current population sizes by census and indirectly, from the linkage disequilibrium found in the genetic surveys. The two types of estimate were highly correlated. Overall we found genetic diversity to be only slightly lower in Britain than across a comparable area in Scandinavia where populations are large and continuous. Whilst the ensemble of British fragments maintain diversity levels close to Scandinavian populations, individually they have drifted apart and lost diversity; particularly the smaller populations. An ABC analysis, based on coalescent models, favours demographic scenarios in which Britain maintained high levels of genetic diversity through post-glacial recolonisation. This diversity has subsequently been partitioned into population fragments that have recently lost diversity at a rate corresponding to the current population-size estimates. We conclude that the British population fragments retain sufficient genetic resources to be the basis of conservation and re-planting programmes. Use of markers with different mutation rates gives us greater confidence and insight than one marker set could have alone, and we suggest that RAD-SSRs are particularly useful as high mutation rate marker set with a well-specified ascertainment bias, which are widely available yet often neglected in existing RAD datasets