Widespread state-dependent shifts in cerebellar activity in locomoting mice

Excitatory drive enters the cerebellum via mossy fibers, which activate granule cells, and climbing fibers, which activate Purkinje cell dendrites. Until now, the coordinated regulation of these pathways has gone unmonitored in spatially resolved neuronal ensembles, especially in awake animals. We imaged cerebellar activity using functional two-photon microscopy and extracellular recording in awake mice locomoting on an air-cushioned spherical treadmill. We recorded from putative granule cells, molecular layer interneurons, and Purkinje cell dendrites in zone A of lobule IV/V, representing sensation and movement from trunk and limbs. Locomotion was associated with widespread increased activity in granule cells and interneurons, consistent with an increase in mossy fiber drive. At the same time, dendrites of different Purkinje cells showed increased co-activation, reflecting increased synchrony of climbing fiber activity. In resting animals, aversive stimuli triggered increased activity in granule cells and interneurons, as well as increased Purkinje cell co-activation that was strongest for neighboring dendrites and decreased smoothly as a function of mediolateral distance. In contrast with anesthetized recordings, no 1-10 Hz oscillations in climbing fiber activity were evident. Once locomotion began, responses to external stimuli in all three cell types were strongly suppressed. Thus climbing and mossy fiber representations can shift together within a fraction of a second, reflecting in turn either movement-associated activity or external stimuli.     

Application of Physiologically Based Absorption Modeling to Formulation Development of a Low Solubility,Low Permeability Weak Base: Mechanistic Investigation of Food Effect

Physiologically based pharmacokinetic (PBPK) modeling has been broadly used to facilitate drug development, hereby we developed a PBPK model to systematically investigate the underlying mechanisms of the observed positive food effect of compound X (cpd X) and to strategically explore the feasible approaches to mitigate the food effect. Cpd X is a weak base with pH-dependent solubility; the compound displays significant and dose-dependent food effect in humans, leading to a nonadherence of drug administration. A GastroPlus Opt logD Model was selected for pharmacokinetic simulation under both fasted and fed conditions, where the biopharmaceutic parameters (e.g., solubility and permeability) for cpd X were determined in vitro, and human pharmacokinetic disposition properties were predicted from preclinical data and then optimized with clinical pharmacokinetic data. A parameter sensitivity analysis was performed to evaluate the effect of particle size on the cpd X absorption. A PBPK model was successfully developed for cpd X; its pharmacokinetic parameters (e.g., C _max, AUC_inf, and t _max) predicted at different oral doses were within ±25% of the observed mean values. The in vivo solubility (in duodenum) and mean precipitation time under fed conditions were estimated to be 7.4- and 3.4-fold higher than those under fasted conditions, respectively. The PBPK modeling analysis provided a reasonable explanation for the underlying mechanism for the observed positive food effect of the cpd X in humans. Oral absorption of the cpd X can be increased by reducing the particle size (<100 nm) of an active pharmaceutical ingredient under fasted conditions and therefore, reduce the cpd X food effect correspondingly.     

Efficient APC/C substrate degradation in cells undergoing mitotic exit depends on K11 ubiquitin linkages

The ubiquitin proteasome system (UPS) directs programmed destruction of key cellular regulators via posttranslational modification of its targets with polyubiquitin chains. These commonly contain Lys-48 (K48)–directed ubiquitin linkages, but chains containing atypical Lys-11 (K11) linkages also target substrates to the proteasome—for example, to regulate cell cycle progression. The ubiquitin ligase called the anaphase-promoting complex/cyclosome (APC/C) controls mitotic exit. In higher eukaryotes, the APC/C works with the E2 enzyme UBE2S to assemble K11 linkages in cells released from mitotic arrest, and these are proposed to constitute an improved proteolytic signal during exit from mitosis. We tested this idea by correlating quantitative measures of in vivo K11-specific ubiquitination of individual substrates, including Aurora kinases, with their degradation kinetics tracked at the single-cell level. All anaphase substrates tested by this methodology are stabilized by depletion of K11 linkages via UBE2S knockdown, even if the same substrates are significantly modified with K48-linked polyubiquitin. Specific examination of substrates depending on the APC/C coactivator Cdh1 for their degradation revealed Cdh1-dependent enrichment of K11 chains on these substrates, whereas other ubiquitin linkages on the same substrates added during mitotic exit were Cdh1-independent. Therefore we show that K11 linkages provide the APC/C with a means to regulate the rate of substrate degradation in a coactivator-specified manner.     

Ocean climate prior to breeding affects the duration of the nestling period in the Atlantic puffin

Time-series covering 23 years for a long-lived seabird, the Atlantic puffin (Fratercula arctica L.) at R?st, northern Norway, was used to explore any indirect effects of climatic variations on chick production. By fitting statistical models on the duration of the nestling period, we found that it may be estimated using the average sea temperature and salinity at 0-20 m depth in March (having a positive and a negative effect, respectively). We propose that when the phytoplankton bloom occurs in early spring, adverse oceanographic conditions, i.e. low temperature and high salinity in March, have a negative effect on puffin reproduction by degradation of the prey availability (mainly Clupea harengus) for chick-feeding adults three months later.     

Local and large-scale climatic variables as predictors of the breeding numbers of endangered Lesser Black-backed Gulls on the Norwegian Coast

In the 1970s and 1980s, the nominate subspecies of the Lesser Black-backed Gull (Larus fuscus fuscus) showed a dramatic drop in breeding numbers on the Norwegian Coast, and in 2000, the population in some colonies was only 10–20% of the population in 1980. This decline has been attributed to the collapse in the stock of Norwegian spring spawning herring (Clupea harengus). In this study, we examined whether local climate (sea and air temperatures), winter NAO (North Atlantic Oscilliation), and the year-class strength and size of 0-group herring could predict the relative changes in breeding numbers between years, mainly after the population collapse. Breeding birds were counted in 19 of the years between 1980 and 2007 in an archipelago on the coast of Helgeland, northern Norway. The best model predicting changes in breeding numbers for the period between 1980 and 2005 (for which data on 0-group herring was available) included mean local air temperature in winter (January–March) and winter NAO, explaining 57% of the variation between years, while the other factors had little effect. When also adding the years 2006–2007 (no herring data), the best model included only mean air temperature in winter, explaining 41% of the variation. In conclusion, the high positive correlation between breeding numbers and climatic factors probably resulted from a higher availability of important fish prey after mild winters, for which 0-group herring presently may only account for a limited proportion. However, this prey might have been of much more importance prior to the population decline.