Protein 4.1B Contributes to the Organization of Peripheral Myelinated Axons

Neurons are characterized by extremely long axons. This exceptional cell shape is likely to depend on multiple factors including interactions between the cytoskeleton and membrane proteins. In many cell types, members of the protein 4.1 family play an important role in tethering the cortical actin-spectrin cytoskeleton to the plasma membrane. Protein 4.1B is localized in myelinated axons, enriched in paranodal and juxtaparanodal regions, and also all along the internodes, but not at nodes of Ranvier where are localized the voltage-dependent sodium channels responsible for action potential propagation. To shed light on the role of protein 4.1B in the general organization of myelinated peripheral axons, we studied 4.1B knockout mice. These mice displayed a mildly impaired gait and motility. Whereas nodes were unaffected, the distribution of Caspr/paranodin, which anchors 4.1B to the membrane, was disorganized in paranodal regions and its levels were decreased. In juxtaparanodes, the enrichment of Caspr2, which also interacts with 4.1B, and of the associated TAG-1 and Kv1.1, was absent in mutant mice, whereas their levels were unaltered. Ultrastructural abnormalities were observed both at paranodes and juxtaparanodes. Axon calibers were slightly diminished in phrenic nerves and preterminal motor axons were dysmorphic in skeletal muscle. βII spectrin enrichment was decreased along the axolemma. Electrophysiological recordings at 3 post-natal weeks showed the occurrence of spontaneous and evoked repetitive activity indicating neuronal hyperexcitability, without change in conduction velocity. Thus, our results show that in myelinated axons 4.1B contributes to the stabilization of membrane proteins at paranodes, to the clustering of juxtaparanodal proteins, and to the regulation of the internodal axon caliber

The node of Ranvier in CNS pathology.

Healthy nodes of Ranvier are crucial for action potential propagation along myelinated axons, both in the central and in the peripheral nervous system. Surprisingly, the node of Ranvier has often been neglected when describing CNS disorders, with most pathologies classified simply as being due to neuronal defects in the grey matter or due to oligodendrocyte damage in the white matter. However, recent studies have highlighted changes that occur in pathological conditions at the node of Ranvier, and at the associated paranodal and juxtaparanodal regions where neurons and myelinating glial cells interact. Lengthening of the node of Ranvier, failure of the electrically resistive seal between the myelin and the axon at the paranode, and retraction of myelin to expose voltage-gated K(+) channels in the juxtaparanode, may contribute to altering the function of myelinated axons in a wide range of diseases, including stroke, spinal cord injury and multiple sclerosis. Here, we review the principles by which the node of Ranvier operates and its molecular structure, and thus explain how defects at the node and paranode contribute to neurological disorders

Sonic enhancement of physical and chemical cleaning of coal

This period, laboratory tests were performed to investigate the effects of coal particle size on the sonically enhanced desliming of Illinois No. 6 coal. Desliming removes fine clay particles which can interfere with surface-controlled cleaning processes, and thus it is an important step prior to beneficiation procedures. A 10-kHz Swen Sonic near-field apparatus, configured for continuous-rinse desliming of coal in the presence of sonic waves, was used in the tests. Comparison of data for sonically deslimed coal and the initial wet-sieved sample showed ash content reduced from 22.2 to 16.5% by weight as a result of exposure to pulsed sonic energy at a 50-second total sonication time. Desliming of isolated coal-mineral composite particles resulted in preferential liberation of mineral-rich undersize material. The ash content of the undersize material varied between 24.2 and 31.2% by weight, showing no systematic decrease as the sonication time increased. Laboratory-scale flotation tests using a Hallimond tube were performed to study the effects of coal oxidation and sonic pretreatment of oxidized coals on the surface-controlled cleaning of coal. Other experiments were conducted to determine the effect of sonication on coal and pyrite surfaces

Development of mercury and chloride monitors for coal gasifiers

Ames Laboratory will develop an integrated sampling and analysis system suitable for on-line monitoring of mercury (Hg) and hydrogen chloride (HCl) in advanced coal-based gasifiers. The objectives of this project are to (1) summarize current technology for monitoring Hg and HCl in gaseous effluents; (2) identify analytical techniques for such determinations in high-temperature, high-pressure gases from coal-based systems for producing electrical power; (3) evaluate promising analytical approaches, and (4) produce reliable on-line monitors which are adaptable to plant-scale diagnostics and process control. For HG, the techniques selected for further consideration were atomic absorption and atomic fluorescence. For HCl, non-dispersive infrared absorption, a dry colorimetric procedure, and ion mobility spectroscopy were selected for testing in the laboratory. Results to date are described

Utilization of coal associated minerals. Quarterly report No. 10, January 1-March 31, 1980

In the preceding quarterly report, it was reported that while sampling the Solvent Refined Coal II (SRC II) pilot plant at Fort Lewis, Washington, the plant went down and vacuum bottoms waste material representing the minerals flow at the last steady state condition were obtained. This plant has been sampled again and samples of the incoming feed coal, sized coal and vacuum bottoms waste material were obtained. As part of our effort to trace the same mineral suite through mining, preparation and conversion, new samples of feed coal, cleaned coal and refuse were obtained from the District 4 commercial preparation plant. This preparation plant supplies coal to the SRC II pilot plant at Fort Lewis, Washington. A study of the thermal insulating properties of fired flyash based structural materials was completed and is included

The influence of sociality on the conservation biology of social insects.

Social insects (ants, bees, wasps and termites) as a group are species rich and ecologically dominant. Many are outstanding “ecological engineers”, or providers of “ecosystem services”, or potential bioindicator species. Few social insects are currently formally classified as Threatened, but this is almost certainly due to a lack of information on population sizes and trends in scarce species. The main influence that sociality has on threats faced by social insects is in reducing effective population sizes, increasing population genetic subdivision and possibly reducing levels of genetic variation relative to solitary species. The main influence that sociality has on threats from social insects is via its role in the ecological success of invasive species, which frequently pose a major hazard to native biotas. In some cases, social features underpinning ecological success in the original range almost certainly contribute to the success of invasive social insects. However, recent studies show or strongly suggest that, in some of the most notoriously invasive populations of ants, bees and wasps, novel social traits have arisen that greatly enhance the rate of spread and ecological competitiveness of these populations. Sociality can therefore represent either a liability or an asset in its contribution to the persistence of social insect populations

Ultra-rapid axon-axon ephaptic inhibition of cerebellar Purkinje cells by the pinceau

International audienceExcitatory synaptic activity in the brain is shaped and balanced by inhibition. Because inhibition cannot propagate, it is often recruited with a synaptic delay by incoming excitation. Cerebellar Purkinje cells are driven by long-range excitatory parallel fiber inputs, which also recruit local inhibitory basket cells. The axon initial segment of each Purkinje cell is ensheathed by basket cell axons in a structure called the pinceau, which is largely devoid of chemical synapses. In mice, we found at the single-cell level that the pinceau mediates ephaptic inhibition of Purkinje cell firing at the site of spike initiation. The reduction of firing rate was synchronous with the presynaptic action potential, eliminating a synaptic delay and allowing granule cells to inhibit Purkinje cells without a preceding phase of excitation. Axon-axon ephaptic intercellular signaling can therefore mediate near-instantaneous feedforward and lateral inhibition