Swept source optical coherence tomography Gabor fusion splicing technique for microscopy of thick samples using a deformable mirror

We present a swept source optical coherence tomography (OCT) system at 1060 nm equipped with a wavefront sensor at 830 nm and a deformable mirror in a closed-loop adaptive optics (AO) system. Due to the AO correction, the confocal profile of the interface optics becomes narrower than the OCT axial range, restricting the part of the B-scan (cross section) with good contrast. By actuating on the deformable mirror, the depth of the focus is changed and the system is used to demonstrate Gabor filtering in order to produce B-scan OCT images with enhanced sensitivity throughout the axial range from a Drosophila larvae. The focus adjustment is achieved by manipulating the curvature of the deformable mirror between two user-defined limits. Particularities of controlling the focus for Gabor filtering using the deformable mirror are presented. © 2015 Society of Photo-Optical Instrumentation Engineers

Mutations in shaking-B prevent electrical synapse formation in the Drosophila giant fiber system

The giant fiber system (GFS) is a simple network of neurons that mediates visually elicited escape behavior in Drosophila. The giant fiber (GF), the major component of the system, is a large, descending interneuron that relays visual stimuli to the motoneurons that innervate the tergotrochanteral jump muscle (TTM) and dorsal longitudinal flight muscles (DLMs). Mutations in the neural transcript from the shaking-B locus abolish the behavioral response by disrupting transmission at some electrical synapses in the GFS. This study focuses on the role of the gene in the development of the synaptic connections. Using an enhancer-trap line that expresses lacZ in the GFs, we show that the neurons develop during the first 30 hr of metamorphosis. Within the next 15 hr, they begin to form electrical synapses, as indicated by the transfer of intracellularly injected Lucifer yellow. The GFs dye-couple to the TTM motoneuron between 30 and 45 hr of metamorphosis, to the peripherally synapsing interneuron that drives the DLM motoneurons at approximately 48 hr, and to giant commissural interneurons in the brain at approximately 55 hr. Immunocytochemistry with shaking-B peptide antisera demonstrates that the expression of shaking-B protein in the region of GFS synapses coincides temporally with the onset of synaptogenesis; expression persists thereafter. The mutation shak-B2, which eliminates protein expression, prevents the establishment of dye coupling shaking-B, therefore, is essential for the assembly and/or maintenance of functional gap junctions at electrical synapses in the GFS

Connexins, innexins and pannexins: Bridging the communication gap.

Multicellular organisms have evolved different mechanisms of intercellular communication, the most direct and quickest of which is through channels that link the cytoplasms of adjacent cells. In plants, a cytoplasmic continuity exists through elongated cytoplasmic bridges termed plasmodesmata, which cross the thick cell walls surrounding plant cells. In metazoans, cells are interconnected by channels which span the two plasma membranes and the intercellular space; these result from the docking of two half channels, which are hexameric torus of junctional proteins around an aqueous pore. These densely packed channels, localised in gap junctions, provide a direct route by which cells can exchange ions and small molecules, including oligonucleotides, siRNAs, and second messengers such as Ca2+, inositol phosphates and cyclic nucleotides. Gap junctions are found in essentially all tissues at some stage of development hinting at an enormous diversity of functions beyond their traditional roles in coordinating electrical activity in excitable tissues. All junctional channels have a similar overall structure but, unlike many other membrane channels, different gene families encode the membrane proteins that form them in different animal phyla (see Fig. 1). For a long time, gap junction structure and functions were mainly investigated in the vertebrates, where they were thought to be formed solely by connexins (Cxs). Then, in Drosophila (an arthropod) and C. elegans (a nematode), which have no Cx genes, gap junctions were found to be composed of another gene family, the innexins (Inxs, invertebrate analogues of Cxs), which have no sequence homology to Cxs [1]. The list of animal phyla with identified Inx family members progressively extended to annelida, platyhelminthes, mollusca and coelenterata. Inxs were also identified in polydnaviruses, symbiotic proviruses of parasitic wasps; these functional genes appear to have originated from, and co-evolved with, host insect innexins (see [2] and [3]). Sequences with low similarity to the invertebrate innexins were identified in vertebrate chordates, leading some authors to suggest that the protein family be re-named pannexins (from the Greek “pan”, neuter of the adjective “pas”, which means all, entire, and nexus, connection ; [4] and [5]. At present the vertebrate proteins and a few invertebrate innexins are referred to as pannexins (abbreviated Panx; see Fig. 1). For clarity, this term will be used here only to refer to the chordate innexin-like sequences. It also emerged that Cx genes were not restricted to vertebrate animals but were also present in invertebrate chordates (e.g. in tunicates, ascidians and appendicularians; see [6] for an analysis of their relationship to vertebrate connexins)