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Ruiz S.,Institute Investigaciones Biologicas Clemente | Ferreiro M.J.,Institute Investigaciones Biologicas Clemente | Menhert K.I.,University of Stockholm | Cantera R.,Institute Investigaciones Biologicas Clemente | Cantera R.,University of Stockholm

Previous studies have shown that the morphology of the neuromuscular junction of the flight motor neuron MN5 in Drosophila melanogaster undergoes daily rhythmical changes, with smaller synaptic boutons during the night, when the fly is resting, than during the day, when the fly is active. With electron microscopy and laser confocal microscopy, we searched for a rhythmic change in synapse numbers in this neuron, both under light:darkness (LD) cycles and constant darkness (DD). We expected the number of synapses to increase during the morning, when the fly has an intense phase of locomotion activity under LD and DD. Surprisingly, only our DD data were consistent with this hypothesis. In LD, we found more synapses at midnight than at midday. We propose that under LD conditions, there is a daily rhythm of formation of new synapses in the dark phase, when the fly is resting, and disassembly over the light phase, when the fly is active. Several parameters appeared to be light dependent, since they were affected differently under LD or DD. The great majority of boutons containing synapses had only one and very few had either two or more, with a 70:25:5 ratio (one, two and three or more synapses) in LD and 75:20:5 in DD. Given the maintenance of this proportion even when both bouton and synapse numbers changed with time, we suggest that there is a homeostatic mechanism regulating synapse distribution among MN5 boutons. © 2013 Ruiz et al. Source

Callejas C.,Institute Investigaciones Biologicas Clemente | Callejas C.,Laboratorio Of Tecnologia Molecular | Gill P.R.,Institute Investigaciones Biologicas Clemente | Gill P.R.,Laboratorio Of Tecnologia Molecular | And 4 more authors.
World Journal of Microbiology and Biotechnology

Cyanobacterial 16S ribosomal RNA gene diversity was examined in a benthic mat on Fildes Peninsula of King George Island (62o09′54. 4′′S, 58o57′20. 9′′W), maritime Antarctica. Environmental DNA was isolated from the mat, a clone library of PCR-amplified 16S rRNA gene fragments was prepared, and amplified ribosomal DNA restriction analysis (ARDRA) was done to assign clones to seven groups. Low cyanobacterial diversity in the mat was suggested in that 83% of the clones were represented by one ARDRA group. DNA sequences from this group had high similarity with 16S rRNA genes of Tychonema bourrellyi and T. bornetii isolates, whose geographic origins were southern Norway and Northern Ireland. Cyanobacterial morphotypes corresponding to Tychonema have not been reported in Antarctica, however, this morphotype was previously found at Ward Hunt Lake (83oN), and in western Europe (52oN). DNA sequences of three of the ARDRA groups had highest similarity with 16S rDNA sequences of the Tychonema group accounting for 9. 4% of the clones. Sequences of the remaining three groups (7. 6%) had highest similarity with 16S rRNA genes of uncultured cyanobacteria clones from benthic mats of Lake Fryxell and fresh meltwater on the McMurdo Ice Shelf. © 2010 Springer Science+Business Media B.V. Source

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