Climate seasonality limits leaf carbon assimilation and wood productivity in tropical forests

The seasonal climate drivers of the carbon cycle in tropical forests remain poorly known, although these forests account for more carbon assimilation and storage than any other terrestrial ecosystem. Based on a unique combination of seasonal pan-tropical data sets from 89 experimental sites (68 include aboveground wood productivity measurements and 35 litter productivity measurements), their associate canopy photosynthetic capacity (enhanced vegetation index, EVI) and climate, we ask how carbon assimilation and aboveground allocation are related to climate seasonality in tropical forests and how they interact in the seasonal carbon cycle. We found that canopy photosynthetic capacity seasonality responds positively to precipitation when rainfall is < 2000 mm.yr−1 (water-limited forests) and to radiation otherwise (light-limited forests); on the other hand, independent of climate limitations, wood productivity and litterfall are driven by seasonal variation in precipitation and evapotranspiration respectively. Consequently, light-limited forests present an asynchronism between canopy photosynthetic capacity and wood productivity. Precipitation first-order control indicates an overall decrease in tropical forest productivity in a drier climate.Peer reviewe

Development of Novel Monoamine Oxidase‑B (MAO-B) Inhibitors with Reduced Blood–Brain Barrier Permeability for the Potential Management of Noncentral Nervous System (CNS) Diseases

Studies indicate that MAO-B is induced in peripheral inflammatory diseases. To target peripheral tissues using MAO-B inhibitors that do not permeate the blood–brain barrier (BBB) the MAO-B-selective inhibitor deprenyl was remodeled by replacing the terminal acetylene with a CO₂H function, and incorporating a <i>para</i>-OCH₂Ar motif (compounds <b>10a</b>–<b>s</b>). Further, in compound <b>32</b> the C-2 side chain corresponded to CH₂CN. In vitro, <b>10c</b>, <b>10j</b>, <b>10k</b>, and <b>32</b> were identified as potent reversible MAO-B inhibitors, and all four compounds were more stable than deprenyl in plasma, liver microsomal, and hepatocyte stability assays. In vivo, they demonstrated greater plasma bioavailability. Assessment of in vitro BBB permeability showed that compound <b>10k</b> is a P-glycoprotein (P-gp) substrate and <b>10j</b> displayed mild interaction. Importantly, compounds <b>10c</b>, <b>10j</b>, <b>10k</b>, and <b>32</b> displayed significantly reduced BBB permeability after intravenous, subcutaneous, and oral administration. These polar MAO-B inhibitors are pertinent leads for evaluation of efficacy in noncentral nervous system (CNS) inflammatory disease models