No abstract

CNS synapse assembly typically follows after stable contacts between "appropriate" axonal and dendritic membranes are made. We show that presynaptic boutons selectively form de novo following neuronal fiber adhesion to beads coated with poly-D-lysine (PDL), an artificial cationic polypeptide. As demonstrated by atomic force and live confocal microscopy, functional presynaptic boutons self-assemble as rapidly as 1 h after bead contact, and are found to contain a variety of proteins characteristic of presynaptic endings. Interestingly, presynaptic compartment assembly does not depend on the presence of a biological postsynaptic membrane surface. Rather, heparan sulfate proteoglycans, including syndecan-2, as well as others possibly adsorbed onto the bead matrix or expressed on the axon surface, are required for assembly to proceed by a mechanism dependent on the dynamic reorganization of F-actin. Our results indicate that certain (but not all) nonspecific cationic molecules like PDL, with presumably electrostatically mediated adhesive properties, can effectively bypass cognate and natural postsynaptic ligands to trigger presynaptic assembly in the absence of specific target recognition. In contrast, we find that postsynaptic compartment assembly depends on the prior presence of a mature presynaptic ending.

Hydrophobe Quantenpunkte können in die Doppelschichtmembran von Lipidvesikeln eingeschlossen und von dort selektiv in Plasmamembranen oder in das Cytoplasma lebender Zellen freigesetzt werden (siehe Bild). Die Zell‐ und Lipidmembranen können jede Art von hydrophoben Nanopartikeln einschließen, deren Größe mit der Membrandicke übereinstimmt, was Möglichkeiten für Einzelzellanwendungen in der Nanobiotechnologie bietet.

Spherical supported bilayer membranes (SS-BLMs) are very attractive candidates in modern bioanalytics and biorecognition studies. A uniform, facile method of preparing different SS-BLMs on silica beads is reported. Confocal fluorescence microscopy and cryo-TEM imaging have been used to characterize these SS-BLMs. Thermal analysis data and FRAP experiments show that the bilayer properties of the SS-BLM are consistent with those of lipid vesicles from which they are formed. The possibility of modulating the size, lipid type and functionality, and mechanical stability makes these rigid liposomes very attractive candidates in biosensors, drug screening, and gene delivery-related applications. This is especially true in work with native vesicle membranes derived from living cells because the existing methods can only accommodate anionic membranes to a limited extent.

To understand the molecular anatomy of myelin membranes, we performed a large-scale, liquid chromatography-coupled tandem mass spectrometry (LC-MS/MS)-based lipidome and proteome screen on freshly purified human and murine myelin fractions. We identified more than 700 lipid moieties and above 1,000 proteins in the two species, including 284 common lipids and 257 common proteins. This study establishes the first comprehensive map of myelin membrane components in human and mice. Although this study demonstrates many similarities between human and murine myelin, several components have been identified exclusively in each species. Future quantitative validation studies focused on interspecies differences will authenticate the myelin membrane anatomy. The combined lipidome and proteome map presented here can nevertheless be used as a reference library for myelin health and disease.

The formation of functional synapses on artificial substrates is a very important step in the development of engineered in vitro neural networks. Spherical supported bilayer lipid membranes (SS-BLMs) are used here as a novel substrate to demonstrate presynaptic vesicle accumulation at an in vitro synaptic junction. Confocal fluorescence microscopy, cryo-transmission electron microscopy (cryo-TEM), and fluorescence recovery after photobleaching (FRAP) experiments have been used to characterize the SS-BLMs. Conventional immunocytochemistry combined with confocal fluorescence microscopy was used to observe the formation of presynaptic vesicles at the neuron-SS-BLM contacts. These results indicate that lipid phases may play a role in the observed phenomenon, in addition to the chemical and electrostatic interactions between the neurons and SS-BLMs. The biocompatibility of lipid bilayers along with their membrane tunability makes the suggested approach a useful "toolkit" for many neuroengineering applications including artificial synapse formation and synaptogenesis in vivo.

Abstract. Congenital lobar emphysema (CLE) and tension pneumothorax (TPT) are rarely reported in dogs. A case of CLE of the right middle lung lobe predisposing to air trapping, alveolar hyperinflation, and pleural rupture resulting in fatal spontaneous TPT in a 6-month-old mixed breed dog is described. The unique alteration of ''bloat line'' was observed in this case in addition to compressive atelectasis of all other lung lobes and lack of negative pressure within the thoracic cavity, signifying markedly elevated intrathoracic pressure. Bronchial cartilage hypoplasia and bronchiectasis were confirmed microscopically, which likely led to abnormal dynamic collapse of bronchi during expiration, consequentially leading to increased intrapulmonary pressure, bullous emphysema, and pleural rupture resulting in TPT. TPT consequent to CLE may therefore be considered one of the potential causes of sudden death in young dogs without overt clinical illness.

Spherically supported bilayer lipid membranes (SS-BLMs) exhibiting co-existing membrane microdomains were created on spherical silica substrates. These 5 μm SiO2-core SS-BLMs are shown to interact dynamically when interfaced with living cells in culture, while keeping the membrane structure and lipid domains on the SS-BLM surface intact. Interactions between the SS-BLMs and cellular components are examined via correlating fluorescently labeled co-existing microdomains on the SS-BLMs, their chemical composition and biophysical properties with the consequent organization of cell membrane lipids, proteins, and other cellular components. This approach is demonstrated in a proof-of-concept experiment involving the dynamic organization of cellular cytoskeleton, monitored as a function of the lipid domains of the SS-BLMs. The compositional versatility of SS-BLMs provides a means to address the relationship between the phenomenon of lipid phase separation and the other contributors to cell membrane lateral heterogeneity.