Light-mediated polarization of the PIN3 auxin transporter for the phototropic response in Arabidopsis.

Phototropism is an adaptation response, through which plants grow towards the light. It involves light perception and asymmetric distribution of the plant hormone auxin. Here we identify a crucial part of the mechanism for phototropism, revealing how light perception initiates auxin redistribution that leads to directional growth. We show that light polarizes the cellular localization of the auxin efflux carrier PIN3 in hypocotyl endodermis cells, resulting in changes in auxin distribution and differential growth. In the dark, high expression and activity of the PINOID (PID) kinase correlates with apolar targeting of PIN3 to all cell sides. Following illumination, light represses PINOID transcription and PIN3 is polarized specifically to the inner cell sides by GNOM ARF GTPase GEF (guanine nucleotide exchange factor)-dependent trafficking. Thus, differential trafficking at the shaded and illuminated hypocotyl side aligns PIN3 polarity with the light direction, and presumably redirects auxin flow towards the shaded side, where auxin promotes growth, causing hypocotyls to bend towards the light. Our results imply that PID phosphorylation-dependent recruitment of PIN proteins into distinct trafficking pathways is a mechanism to polarize auxin fluxes in response to different environmental and endogenous cues.

Spatial distribution of motor units recruited during electrical stimulation of the quadriceps muscle versus the femoral nerve.

INTRODUCTION: In this study we investigated differences in the spatial recruitment of motor units (MUs) in the quadriceps when electrical stimulation is applied over the quadriceps belly versus the femoral nerve. METHODS: M-waves and mechanical twitches were evoked using over-the-quadriceps and femoral nerve stimulation of gradually increasing intensity from 22 young, healthy subjects. Spatial recruitment was investigated using recruitment curves of M-waves recorded from the vastus medialis (VM) and vastus lateralis (VL) and of twitches recorded from the quadriceps. RESULTS: At maximal stimulation intensity (Imax), no differences were found between nerve and over-the-quadriceps stimulation. At submaximal intensities, VL M-wave amplitude was higher for over-the-quadriceps stimulation at 40% Imax, and peak twitch force was greater for nerve stimulation at 60% and 80% Imax. CONCLUSIONS: For the VM, MU spatial recruitment during nerve and over-the-quadriceps stimulation of increasing intensity occurred in a similar manner, whereas significant differences were observed for the VL. Muscle Nerve, 2013.

Test-retest repeatability of the pupil light response to blue and red light stimuli in normal human eyes using a novel pupillometer.

In this study, we evaluated the repeatability of pupil responses to colored light stimuli in healthy subjects using a prototype chromatic pupillometer. One eye of 10 healthy subjects was tested twice in the same day using monochromatic light exposure at two selected wavelengths (660 and 470 nm, intensity 300 cd/m(2)) presented continuously for 20 s. Pupil responses were recorded in real-time before, during, and after light exposure. Maximal contraction amplitude and sustained contraction amplitude were calculated. In addition, we quantified the summed pupil response during continuous light stimulation as the total area between a reference line representing baseline pupil size and the line representing actual pupil size over 20 s (area under the curve). There was no significant difference in the repeated measure compared to the first test for any of the pupil response parameters. In conclusion, we have developed a novel prototype of color pupillometer which demonstrates good repeatability in evoking and recording the pupillary response to a bright blue and red light stimulus.

Spatial variation in the decline of European birds as shown by the barn owl Tyto alba diet

Capsule The analysis of 635 papers about the diet of the European Barn Owl Tyto alba showed that 83 751 birds were captured out of 3.44 million prey items (2.4%). Birds were more frequently captured on islands than mainland, in southern than northern Europe and in eastern than western Europe. Between 1860 and 2012, the consumption of birds decreased in northern and eastern Europe. Among avian prey, the House Sparrow Passer domesticus, the most frequently captured bird (65.7%), decreased in frequency during the last 150 years in eastern Europe.