Subcellular mapping of dendritic activity in optic flow processing neurons

Dendritic integration is a fundamental element of neuronal information processing. So far, few studies have provided a detailed spatial picture of this process, describing the properties of local dendritic activity and its subcellular organization. Here, we used 2-photon calcium imaging in optic flow processing neurons of the fly Calliphora vicina to determine the preferred location and direction of local motion cues for small branchlets throughout the entire dendrite. We found a pronounced retinotopic mapping on both the subcellular and the cell population level. In addition, dendritic branchlets residing in different layers of the neuropil were tuned to distinct directions of motion. Summing the local receptive fields of all dendritic branchlets reproduced the characteristic properties of these neurons’ axonal output receptive fields. Our results corroborate the notion that the dendritic morphology of vertical system cells allows them to selectively collect local motion inputs with particular directional preferences from a spatially organized input repertoire, thus forming filters that match global patterns of optic flow. Furthermore, we suggest that the facet arrangement across the fly’s eye shapes the subcellular direction tuning to local motion stimuli. These data illustrate a highly structured circuit organization as an efficient way to hard-wire a complex sensory task.     

Cytolysis of Free-Living Algae by Complement

Cells of Euglena gracilis show a marked change in cell shapewhen normal rat serum is added—they contract assuminga spherical shape. Contraction is followed by irreversible cytolysis.Examination of lysed cells by electron microscopy revealed numerouslesions of about 10 nm inner diameter in the cell membrane.However, heat-inactivated sera neither affected the characteristicelongated state of Euglena nor caused any lesions in the cellmembrane. Assay using radiolabelled (¹²⁵1) anti C5b-C9(m) antibodiesshowed that the lytic complexes are integrated into the cellmembrane of Euglena. When C4-deficient and factor D-depletedsera were used as complement sources, the results showed thatthe killing of Euglena was dependent on an intact alternativepathway of the complement. This serum-mediated lysis of algaealso occurred in different systematic groups: Chilomonas paramecium(Cryptophyceae), Chroomonas spec. (Cryptophyceae), Ochromonasdanica (Chrysophyceae), Astasia longa (Euglenophyceae), Distigmaelegans (Euglenophyceae), and Polytomella spec. (Chlorophyceae). (Received May 28, 1986; Accepted September 16, 1986)     

Electrocatalytic evidence of the diversity of the oxygen reaction in the bacterial bd oxidase from different organisms

Cytochrome bd oxidase is a bacterial terminal oxygen reductase that was suggested to enable adaptation to different environments and to confer resistance to stress conditions. An electrocatalytic study of the cyt bd oxidases from Escherichia coli, Corynebacterium glutamicum and Geobacillus thermodenitrificans gives evidence for a different reactivity towards oxygen. An inversion of the redox potential values of the three hemes is found when comparing the enzymes from different bacteria. This inversion can be correlated with different protonated glutamic acids as evidenced by reaction induced FTIR spectroscopy. The influence of the microenvironment of the hemes on the reactivity towards oxygen is discussed.     

Binary regression: Total gain in positive and negative predictive values

Models that predict disease incidence or disease recurrence are attractive for clinicians as well as for patients. The usefulness of a risk prediction model is linked to the two questions whether the observed outcome is confirmed by the prediction and whether the risk prediction is accurate in predicting the future outcome, respectively. The first phrasing of the question is linked to considering sensitivity and specificity and the latter to the positive and negative predictive values. We present the measures of standardized total gain in positive and negative predictive values dealing with the performance or accuracy of the prediction model for a binary outcome. Both measures provide a useful tool for assessing the performance or accuracy of a set of predictor variables for the prediction of a binary outcome. This concept is a tool for evaluating the optimal prediction model in future research.     

Dose-dependent improvement of myoclonic hyperkinesia due to Valproic acid in eight Huntington's Disease patients: a case series

Background  

Chorea in Huntington's Disease (HD) is usually treated with antidopaminergic neuroleptics like haloperidol, olanzapine and tiaprid or dopamine depleting drugs like tetrabenazine. Some patients with hyperkinesia, however, react to treatment with antidopaminergic drugs by developing extrapyramidal side effects. In earlier studies valproic acid showed no beneficial effect on involuntary choreatic movements. Myoclonus is rare in HD and is often overseen or misdiagnosed as chorea.     

Acceptor-photobleaching FRET analysis of core kinetochore and NAC proteins in living human cells

Faithful chromatin segregation is mediated and controlled by the kinetochore protein network which assembles at centromeres. In this study, the neighbourhood relations of inner kinetochore and nucleosome-associated complex (NAC) proteins were analysed in living human interphase cells by acceptor photobleaching FRET. The data indicate that CENP-U is in close vicinity to CENP-I as well as to CENP-B and that CENP-M is close to CENP-T. This article has been submitted as a contribution to the Festschrift entitled “Uncovering cellular sub-structures by light microscopy” in honour of Professor Cremer’s 65th birthday.     

Assisted Colonization: A Question of Focal Units and Recipient Localities

Assisted colonization as an adaptation strategy to conserve or restore biodiversity in the face of climate change deservedly evokes controversy. Assisted colonization is perceived by some as a last option for conserving endangered species and by others as a risky and unwise management effort due to current gaps of knowledge. Based on the pros and cons of the recent debate, we show that the current discussion mainly focuses on the assisted colonization of rare and endangered species beyond their natural range of distribution. We suggest that a more useful approach for the conservation of endangered species could occur by focusing on the relevant foundation or keystone species, which ensure ecosystem integrity for a multitude of dependent species by governing the habitat structure and micro‐climate of the site. Examples of foundation species include dominant tree species in forests or dominant corals in coral reefs. For a given conservation or restoration need (e.g. conservation of rare species), we recommend the assisted colonization of pre‐adapted ecotypes of the relevant foundation species from climates similar to future expectations for the target site. This approach could lead to climate‐safe habitats for endangered species with minimal adverse effects on recipient ecosystems.