Brain potentials associated with pattern displacement and saccadic eye movements in humans and rhesus monkeys

Visual evoked potentials (VEPs) to the onset of motion of visual patterns and brain responses associated with saccadic eye movements (SRPs) were compared in human subjects and in rhesus monkeys. Three different velocities of pattern motion were employed. In humans, brain responses were recorded from six scalp areas. In monkeys, transcortical recordings were obtained from chronically implanted electrodes in the occipital, temporo-parietal, and frontal areas. In humans there was a clear difference in VEPs to the pattern motion between the anterior (Fz, Cz) and posterior (Pz, Oz) scalp regions. The earliest component was a positive peak at 85 ms at Oz followed by a negativity around 110 ms. In the fronto-central leads the VEP was characterized by a negativity at 145 ms and a subsequent broad positive component around 250 ms. SRP responses differed in the early components from the VEPs to pattern motion but a good correspondence was found in the morphology of the late components of the two types of brain potentials. Furthermore, flashed-on VEPs and SRPs elicited a late positivity of more pronounced amplitude than VEPs to pattern displacement. In monkeys similar findings were found: an early negative component of the pattern-displacement VEP could not be observed in the SRP responses over the visual cortex while the late portion of the SRP waveform was greater than the late positivity of the VEP to motion-onset.     

Study of the effect of volatile substances from cereal roots

We traced the liberation and biological effect of volatile substances released from the roots of cereals,i. e. barley, wheat, rye and oats, on seedlings of the same and other plant species. Experiments were carried out in a closed glass apparatus with a static or circulating atmosphere in which the CO₂ and O₂ were permanently absorbed and supplemented, respectively. In some experiments the air was bubbled through water or through solutions of boric acid, barium hydroxide and potassium permanganate. The roots of all four cereals tested released volatile substances with a biological activity which appeared to be non-specific with respect to plant species. The effect of volatile substances was partially decreased by bubbling through water, barium hydroxide and boric acid and was completely removed after passing through the solution of potassium permanganate. Volatile substances liberated from roots of barley inhibited elongation of roots and coleoptile, decreased SH-group content and caused excessive formation of root hairs as well as inhibition of both dry matter production and respiration of roots of rye seedlings. Ethylene was found in the atmosphere of experimental vessels.     

Bilayered clathrin coats on endosomal vacuoles are involved in protein sorting toward lysosomes

In many cells endosomal vacuoles show clathrin coats of which the function is unknown. Herein, we show that this coat is predominantly present on early endosomes and has a characteristic bilayered appearance in the electron microscope. By immunoelectron microscopy we show that the coat contains clathrin heavy as well as light chain, but lacks the adaptor complexes AP1, AP2, and AP3, by which it differs from clathrin coats on endocytic vesicles and recycling endosomes. The coat is insensitive to short incubations with brefeldin A, but disappears in the presence of the phosphatidylinositol 3-kinase inhibitor wortmannin. No association of endosomal coated areas with tracks of tubulin or actin was found. By quantitative immunoelectron microscopy, we found that the lysosomal-targeted receptors for growth hormone (GHR) and epidermal growth factor are concentrated in the coated membrane areas, whereas the recycling transferrin receptor is not. In addition, we found that the proteasomal inhibitor MG 132 induces a redistribution of a truncated GHR (GHR-369) toward recycling vesicles, which coincided with a redistribution of endosomal vacuole-associated GHR-369 to the noncoated areas of the limiting membrane. Together, these data suggest a role for the bilayered clathrin coat on vacuolar endosomes in targeting of proteins to lysosomes.     

Ubiquitin: same molecule, different degradation pathways

Ubiquitin is a common demoninator in the targeting of substrates to all three major protein degradation pathways in mammalian cells: the proteasome, the lysosome, and the autophagosome. The factors that direct a substrate toward a particular route of degradation likely include ubiquitin chain length and linkage type, which may favor interaction with particular receptors or confer differential susceptibility to deubiquitinase activities associated with each pathway.     

The emerging shape of the ESCRT machinery

The past two years have seen an explosion in the structural understanding of the endosomal sorting complex required for transport (ESCRT) machinery that facilitates the trafficking of ubiquitylated proteins from endosomes to lysosomes via multivesicular bodies (MVBs). A common organization of all ESCRTs is a rigid core attached to flexibly connected modules that recognize other components of the MVB pathway. Several previously unsuspected key links between multiple ESCRT subunits, phospholipids and ubiquitin have now been elucidated, which, together with the detailed morphological analyses of ESCRT-depletion phenotypes, provide new insights into the mechanism of MVB biogenesis.     

Humpback whale abundance in the North Pacific estimated by photographic capture‐recapture with bias correction from simulation studies

We estimated the abundance of humpback whales in the North Pacific by capture‐recapture methods using over 18,000 fluke identification photographs collected in 2004–2006. Our best estimate of abundance was 21,808 (CV = 0.04). We estimated the biases in this value using a simulation model. Births and deaths, which violate the assumption of a closed population, resulted in a bias of +5.2%, exclusion of calves in samples resulted in a bias of ?10.5%, failure to achieve random geographic sampling resulted in a bias of ?0.4%, and missed matches resulted in a bias of +9.3%. Known sex‐biased sampling favoring males in breeding areas did not add significant bias if both sexes are proportionately sampled in the feeding areas. Our best estimate of abundance was 21,063 after accounting for a net bias of +3.5%. This estimate is likely to be lower than the true abundance due to two additional sources of bias: individual heterogeneity in the probability of being sampled (unquantified) and the likely existence of an unknown and unsampled breeding area (?8.7%). Results confirm that the overall humpback whale population in the North Pacific has continued to increase and is now greater than some prior estimates of prewhaling abundance.